lab000040
10.3205/lab000040
urn:nbn:de:0183-lab0000409
Report
Quality of bacteriological infection serology in Germany: analysis of the 2017 proficiency testing trials
Zur Qualität bakteriologisch-infektionsserologischer Verfahren in Deutschland: Auswertung der infektionsserologischen Ringversuche 2017
Smit
Smit
Renata
R
Dr.
Institute for Laboratory Medicine, Microbiology and Infection Control, Northwest Medical Centre, Academic Teaching Hospital, Medical Faculty, Goethe University, Steinbacher Hohl 2–26, 60488 Frankfurt am Main, GermanyInstitute for Laboratory Medicine, Microbiology and Infection Control, Northwest Medical Centre, Academic Teaching Hospital, Medical Faculty, Goethe University, Frankfurt am Main, GermanyINSTAND e.V., Düsseldorf, Germany
renata_smit@t-2.net
author
Hunfeld
Hunfeld
Klaus-Peter
KP
Institute for Laboratory Medicine, Microbiology and Infection Control, Northwest Medical Centre, Academic Teaching Hospital, Medical Faculty, Goethe University, Frankfurt am Main, Germany
INSTAND e.V., Düsseldorf, Germany
German Society for Hygiene and Microbiology, Safety of Quality commission, Hannover, Germany
author
German Medical Science GMS Publishing House
Düsseldorf
610
external quality assurance
EQA
proficiency testing trials
bacteriological infection serology
Germany
externe Qualitätssicherung
EQA
Ringversuche
bakteriologische Infektionsserologie
Deutschland
20201207
engl
This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 License.
Dieser Artikel ist ein Open-Access-Artikel und steht unter den Lizenzbedingungen der Creative Commons Attribution 4.0 License (Namensnennung).
1869-4241
11
GMS Zeitschrift zur Förderung der Qualitätssicherung in medizinischen Laboratorien
GMS Z Forder Qualitatssich Med Lab
05
Bakteriologisch-serologische Tests können bakterielle Antigene und Antikörper (IgG und IgM) in einer Probe von Körperflüssigkeiten nachweisen, um die Diagnose von Krankheiten zu erleichtern, den Immun- und Impfstatus von Patienten zu untersuchen oder die Ausbreitung von Infektionen zu kontrollieren. Die Teilnahme von Laboratorien an der externen Leistungssicherung (EQA) kann den Vergleich von Leistung und Ergebnissen zwischen verschiedenen Laboratorien ermöglichen, um ein angemessenes diagnostisches Qualitätsmanagement und damit eine hohe Präzision der Testergebnisse zu gewährleisten, die zu einer genauen und schnellen Behandlung führen kann. Der vorliegende Beitrag fasst die Ergebnisse der bakteriologischen Infektionsserologie als Teil der 2017 durchgeführten Ringversuche zusammen und diskutiert sie mit dem Ziel, das diagnostische Management der Laboratorien in Deutschland zu verbessern.
Bacteriological serological tests can detect bacterial antigens and antibodies (IgG and IgM) in samples of body fluids to help diagnose diseases, assess a patient’s immune and vaccination status and control the spread of infections. Participation by laboratories in external quality assurance (EQA) enables the comparison of performance and results among different laboratories. This ensures an appropriate quality management for diagnostic testing and, thus, highly precise test results that lead to accurate and rapid treatment. This paper summarizes and discusses the results of the bacteriological infectious serology as part of proficiency testing trials conducted in 2017 and aims to improve the diagnostic management of laboratories in Germany.
1 IntroductionSerological tests can be used to detect viral and bacterial antigens and antibodies (IgG and IgM) in a sample of blood, cerebrospinal fluid (CSF) or urine . Serological testing is often used to help diagnose diseases, assess a patient’s immune and vaccination status, and control the spread of infection in a certain population , , . Selecting the appropriate test can lead to a fast, accurate interpretation of the diagnostic findings, as well as proper and immediate treatment . All tests have to meet standard operating procedures and should be validated or verified to comply with the laboratory’s quality management. Participation in external quality assurance (EQA) can ensure the accuracy of the diagnostic test results. EQA also allows a comparison of performance and results between different laboratories, the identification of problems associated with equipment, methods and materials, and the improvement of quality management. It also identifies training needs and monitors the role of training and its impact. EQA helps to assure physicians, patients and health authorities that the laboratory is producing reliable results. EQA participation is usually required for accreditation , . This paper summarizes and discusses the results of bacteriological infection serology as part of proficiency testing trials conducted in 2017. The findings can help to improve the diagnosis of individual constellations and optimize the test systems used. This paper deals with a standardized form.
2 Methods2.1 ParticipantsIn 2017, 125,999 laboratories participated in two proficiency testing trials. 10,640 participants were from Germany and 1,450 were from other European countries. One trial was carried out in May and the other in November 2017 (Table 1 ).2.2 Sample collection and EQA progressAs the proficiency testing provider, the Society for Promoting Quality Assurance in Medical Laboratories e.V. (INSTAND e.V., Düsseldorf) in Germany sent unknown control samples (31, 32, 61 and 62) for each study group (310–334) to participating laboratories twice per year to test for one or more components present in the samples , . All samples were prepared according to standard operating procedures , . Samples 31 and 32 were sent to participating laboratories in May 2017, while samples 61 and 62 were sent in November 2017 , . The control samples for Yersinia, Bordetella pertussis, Campylobacter, Mycoplasma pneumonia and Coxiella burnetii were only analyzed once that year , .2.3 Target valuesThe results of all laboratories were compared to the assigned target value that was determined with the highest level of accuracy and precision using a reference measurement procedure in line with the guideline of the German Medical Association (RiLiBÄK). When a uniform target value could not be determined for the quantitative test results, the robust mean of all participants was established as the target value. With respect to the qualitative test results, either the mode of the results of the reference laboratories or the mode of the results of the participants was set as the target value , , .
3 Results3.1 Tetanus toxoid (310)3.1.1 Sample informationSamples 31, 32, 61 and 62 originated from clinically healthy blood donors.3.1.2 Determination of the target valuesFor the tests conducted in May, the mode of the results of all participants was set as the target value for the qualitative test results, while the mode of the results of the reference laboratories was established as the target value for the semi-quantitative test results. For the November tests, the mode of the results of the reference laboratories was set as the target value for the qualitative test results, while the robust mean of all participants was established as the target value for the semi-quantitative test results , . The results are listed in Table 2 .3.1.3 Overall diagnostic interpretation and commentary on the test resultsAntibody detection has no diagnostic relevance in determining a tetanus infection, but it can be used to assess an individual’s immune or vaccination status for tetanus toxoid . Results of this trial show that samples 31, 61 and 62 had tetanus toxoid antibody titers ranging from 1.4 to 2.9 IU/ml, suggesting protective immunity against tetanus toxoid; however, a booster vaccination would be needed in 5 to 10 years to achieve long-term protection. The level of antibodies in sample 32 was 0.9 IU/ml, suggesting that there was protective immunity; however, a booster vaccination would be needed in 2 to 5 years to provide long-term protection. It is important to note that vaccinations should primarily be done in accordance with the recommendations of the German Standing Committee on Vaccination (STIKO) and not based simply on measured antibody levels . Pass rates for ELISA tests were 100% for the qualitative results and 81.5–96.8% for the quantitative results. The pass rate for the overall diagnostic results was between 98.5% and 99.3%.3.2 Treponema pallidum antibodies (311)3.2.1 Sample informationSamples 32 and 62 originated from healthy blood donors without clinical evidence of syphilis. Sample 31 was taken from a patient with a known syphilis infection that had been sufficiently treated in the past. Sample 61 was donated during blood donor screening by an individual that had been treated for a syphilis infection several years ago.3.2.2 Determination of the target valuesFor the qualitative test results, the mode of the results of the reference laboratories was set as the target value. In the case of the semi-quantitative test results, the mode of the results of all participants was set as the target value for the May tests, while the results of the reference laboratories were stipulated as the target value for November , . The results are listed in Table 3 .3.2.3 Overall diagnostic interpretation and commentary on the test resultsSamples 32 and 62 showed no clinical or serological evidence of a syphilis infection. In the positive sampl<![CDATA[e 3</PlainText></TextGroup>1 (target value (modal): TPPA: 320, VDRL: negative, IgM-FTA-ABS: negative), the results clearly indicated a past infection without the need for further treatment because the IgM-FTA-ABS test was negative. The overall pass rate of all test methods in sample 31 was 77.2%. The positive sample 61 (target value: TPPA: 640, polyval. ELISA: positive, IgG-ELISA: positive, VDRL: negative, FTA-ABS-Ig<TextGroup><PlainText>G: 8</PlainText></TextGroup>0, FTA-ABS-IgM and IgM-ELISA: negative) indicated a syphilis infection and achieved an overall pass rate for all test methods of 86.9%. The distribution of the immunoblot bands for the positive samples 31 (Figure 1 <ImgLink imgNo="1" imgType="figure"/>, Figure 2 <ImgLink imgNo="2" imgType="figure"/>) and 61 (Figure 3 <ImgLink imgNo="3" imgType="figure"/>) are shown below <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The pass rates for the overall diagnostic results of the negative sample<TextGroup><PlainText>s 3</PlainText></TextGroup>2 and 62 were between 96.4% and 98.8%, whereas the pass rates of the positive samples 31 and 61 were between 77.2% and 86.9%.</Pgraph><SubHeadline>3.3 Chlamydia trachomatis antibodies (312)</SubHeadline><SubHeadline2>3.3.1 Sample information</SubHeadline2><Pgraph>Samples 31, 32, 61 and 62 originated from clinically healthy blood donors.</Pgraph><SubHeadline2>3.3.2 Determination of the target values</SubHeadline2><Pgraph>The mode of the results of the reference laboratories was set as the target value for the qualitative test results, while for the semi-quantitative results, the mode of the results of all participants was set as the target value <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are listed in Table 4 <ImgLink imgNo="4" imgType="table"/>.</Pgraph><SubHeadline2>3.3.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>Samples 32 and 61 showed no serological evidence of a <Mark2>C. trachomatis</Mark2> infection. In sample 31, IgG antibodies by ELISA C. spp and blot as well as IgA-ELISA C. spp were detected, indicating an infection with <Mark2>C. trachomatis</Mark2>. In sample 62, IgG and IgA antibodies were detected, suggesting an infection with <Mark2>C. trachomatis</Mark2>. In sample 61, the lowest pass rate was 50% for the qualitative detection of IgG antibodies by immunoblot. In sample 31, the lowest pass rates for the qualitative detection of IgG antibodies by immunoblot and ELISA were 50% and 50.9% respectively. The pass rates for the overall diagnostic results of the negative samples (samples 32 and 61) were between 76.1% and 98.8%, while the pass rates for the positive samples (samples 31 and 62) were between 86.7% and 98.4%.</Pgraph><SubHeadline>3.4 Chlamydia trachomatis antibodies – direct detection by ELISA/PCR (313)</SubHeadline><SubHeadline2>3.4.1 Sample information</SubHeadline2><Pgraph>Samples 31, 32, 61 and 62 originated from clinically healthy blood donors.</Pgraph><SubHeadline2>3.4.2 Determination of the target values</SubHeadline2><Pgraph>For the qualitative test results, the mode of the results of all participants was set as the target value. In the case of the semi-quantitative test results, the mode of the results of the reference laboratories was established as the target value for the tests conducted in May, while the mode of the results of all participants was stipulated as the target value for November <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are presented in Table 5 <ImgLink imgNo="5" imgType="table"/>.</Pgraph><SubHeadline2>3.4.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>Samples 31 and 62 showed no clinical or serological evidence of <Mark2>C. trachomatis</Mark2>, while samples 32 and 61 tested positive for the pathogen, indicating a <Mark2>C. trachomatis</Mark2> infection. The pass rate of all samples for the overall clinical diagnostic results was 100%.</Pgraph><SubHeadline>3.5 Chlamydia pneumonia antibodies (314)</SubHeadline><SubHeadline2>3.5.1 Sample information</SubHeadline2><Pgraph>Samples 31, 32, 61 and 62 were taken from clinically healthy blood donors.</Pgraph><SubHeadline2>3.5.2 Determination of the target values</SubHeadline2><Pgraph>For the tests conducted in May, the results of the reference laboratories was set as the target value for the qualitative results, while for the semi-quantitative test results, the mode of the results of the reference laboratories was set as the target value. For November, the mode of the results of the reference laboratories was set as the target value for the qualitative test results, while for the semi-quantitative results, the mode of the results of all participants was set as the target value <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results and pass rates are shown in Table 6 <ImgLink imgNo="6" imgType="table"/>.</Pgraph><SubHeadline2>3.5.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>In samples 32, 61 and 62, no evidence of an infection with <Mark2>C. pneumoniae</Mark2> was detected, while the test results for the tested pathogen in sample 31 were positive. In sample 31, IgG was detected, with borderline positive results for IgA antibodies, indicating an infection with <Mark2>C</Mark2><TextGroup><Mark2>. p</Mark2></TextGroup><Mark2>neumoniae</Mark2>. All samples had qualitative results of 84.6–100% for all ELISA tests. All MIFT tests were between 66.7 and 100% with respect to the qualitative results and in a range of 64.7–100% for the quantitative results. The pass rates for overall diagnostic results of the negative samples 32, 61 and 62 were between 96.8% and 100%, while for the positive sample 31, the pass rate was 98.2%.</Pgraph><SubHeadline>3.6 Yersinia antibodies (315)</SubHeadline><SubHeadline2>3.6.1 Sample information</SubHeadline2><Pgraph>Sample 31 was obtained from a healthy blood donor. Sample 32 was donated by a patient with gastroenteritis and arthralgia in his recent medical history.</Pgraph><SubHeadline2>3.6.2 Determination of the target values</SubHeadline2><Pgraph>For the tests conducted in May, the mode of the results of all participants was set as the target value for the qualitative test results, while for the semi-quantitative test results, the mode of the results of the reference laboratories was set as the target value. However, in November, the mode of the results of the reference laboratories was set as the target value for the qualitative test results, while the results of the reference laboratories were stipulated as the target value of the semi-quantitative results <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are listed in Table 7 <ImgLink imgNo="7" imgType="table"/>.</Pgraph><SubHeadline>3.7 Chlamydia trachomatis antibodies – direct detection by IFT (316)</SubHeadline><SubHeadline2>3.7.1 Sample information</SubHeadline2><Pgraph>Samples 31, 32, 61 and 62 were taken from clinically healthy blood donors.</Pgraph><SubHeadline2>3.7.2 Determination of the target values </SubHeadline2><Pgraph>The mode of the results of all participants was established as the target value for the qualitative test results <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are listed in Table 5 <ImgLink imgNo="5" imgType="table"/>.</Pgraph><SubHeadline2>3.7.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>Samples 32 and 62 showed no serological evidence of <Mark2>C. trachomatis</Mark2>, while samples 31 and 61 tested positive for the pathogen, indicating an infection with <Mark2>C. trachomatis</Mark2>. The pass rates for the overall diagnostic results of the negative samples 32 and 62 were between 95.7% and 100% and thus in line with previous years, while the pass rate for the positive samples 31 and 61 was 100%.</Pgraph><SubHeadline>3.8 Bordetella pertussis antibodies (317)</SubHeadline><SubHeadline2>3.8.1 Sample information</SubHeadline2><Pgraph>Samples 61 and 62 were donated by healthy blood donors without evidence of any respiratory infections in their recent medical history.</Pgraph><SubHeadline2>3.8.2 Determination of the target values</SubHeadline2><Pgraph>For the qualitative test results, the mode of the results of the reference laboratories was set as the target value, while for the semi-quantitative test results, the robust mean of all participants was established as the target value <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are listed in Table 8 <ImgLink imgNo="8" imgType="table"/>.</Pgraph><SubHeadline>3.9 Diphtheria toxoid antibodies (318)</SubHeadline><SubHeadline2>3.9.1 Sample information</SubHeadline2><Pgraph>Samples 61 and 62 were donated by healthy pre-immunized blood donors, while samples 31 and 32 originated from clinically healthy blood donors.</Pgraph><SubHeadline2>3.9.2 Determination of the target values</SubHeadline2><Pgraph>In the case of the semi-quantitative test results, the r<TextGroup><PlainText>obu</PlainText></TextGroup>st mean of all participants was established as the target value. For the qualitative test results, the mode of the results of the reference laboratories was set as the target value for the May tests, while for November, the mode of the results of all participants was set as the target value <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are shown in Table 9 <ImgLink imgNo="9" imgType="table"/>.</Pgraph><SubHeadline2>3.9.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>Antibody detection against the diphtheria toxin and toxoid (DT) is not suitable for identifying an acute case of diphtheria; it can only be used to assess the immune and vaccination status for diphtheria <TextLink reference="3"></TextLink>. Findings suggested that protective immunity did exist in samples 61 and 62, while in sample 31, there was no protective immunity, therefore a booster vaccination was recommended. The titer level (0.922 IU/ml) of sample 32 indicated protective active immunity, however, a booster vaccination would be needed to provide long-term protection. Vaccination recommendations should primarily be made following STIKO recommendations <TextLink reference="3"></TextLink>. ELISA tests had qualitative results of 100% and quantitative results of 88.1–97.6%. The pass rates for the overall diagnostic results were in the range of 96.0–100%.</Pgraph><SubHeadline>3.10 Campylobacter antibodies (319)</SubHeadline><SubHeadline2>3.10.1 Sample information</SubHeadline2><Pgraph>Samples 31 and 32 originated from clinically healthy blood donors.</Pgraph><SubHeadline2>3.10.2 Determination of the target values</SubHeadline2><Pgraph>The mode of the results of the reference laboratories was set as the target value for the qualitative test results. In the case of the semi-quantitative test results, the mode of the results of all participants was set as the target value for the May tests; however, the robust mean of all participants was established as the target value <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink> for November. The results are listed in Table 10 <ImgLink imgNo="10" imgType="table"/>.</Pgraph><SubHeadline2>3.10.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>Specific IgG, IgM and IgA antibodies were detected using the commercially available ELISA, immunoblot and IFT tests. No evidence of an infection with <Mark2>C. jejuni</Mark2> was detected in sample 32, while sample 31 tested positive for IgG antibodies against the tested pathogen, indicating a <Mark2>Campylobacter</Mark2> infection. In sample 31, qualitative and quantitative results for ELISA were 100% for IgG, IgM and IgA antibodies, while in sample 32 they ranged from 91.7–100%. The pass rate for the overall diagnostic results of sample 32 was 96.52%, while it was 86.8% for sample 31.</Pgraph><SubHeadline>3.11 Procalcitonin (320)</SubHeadline><SubHeadline2>3.11.1 Sample information</SubHeadline2><Pgraph>Samples 31, 32, 61 and 62 were donated by healthy blood donors.</Pgraph><SubHeadline2>3.11.2 Determination of the target values</SubHeadline2><Pgraph>The mode of the results of the reference laboratories was set as the target value for the qualitative test results, while the robust mean of all participants was established as the target value for the semi-quantitative test results <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are presented in Table 11 <ImgLink imgNo="11" imgType="table"/>.</Pgraph><SubHeadline2>3.11.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>The findings of samples 32 and 66 indicated the likel<TextGroup><PlainText>ihoo</PlainText></TextGroup>d of systemic inflammatory reaction (sepsis), while the findings of samples 31 and 61 indicated that systemic infection is unlikely. The qualitative result in all four samples was 100%. The quantitative test results in samples 31 and 61 were 100%, while they were 92.8% in sample 32, and 95.6% in sample 62. The semi-quantitative results in samples 31 and 32 were 100%, while they were 93.8% in samples 61 and 62. The overall d<TextGroup><PlainText>iagnost</PlainText></TextGroup>ic evaluation of all four samples was between 89.5 and 100%.</Pgraph><SubHeadline>3.12 Streptococci antibodies (321)</SubHeadline><SubHeadline2>3.12.1 Sample information</SubHeadline2><Pgraph>Samples 31 and 32 were donated by healthy blood donors.</Pgraph><SubHeadline2>3.12.2 Determination of the target values</SubHeadline2><Pgraph>The mode of the results of the reference laboratories was set as the target value for the qualitative test results, while in the case of the semi-quantitative test results, the robust mean of all participants was established as the target value <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are displayed in <TextGroup><PlainText>Table 12 </PlainText></TextGroup><ImgLink imgNo="12" imgType="table"/>.</Pgraph><SubHeadline2>3.12.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>In the qualitative results, titers of streptococcal antibodies above the cut-off value (200 IU/ml) indicated an infection with <Mark2>Streptococcus</Mark2>. Titers between 200 and 400 indicated a past or recent infection <TextLink reference="5"></TextLink>. A much higher titer occurs when there is severe infection or an acute secondary disease. The latex agglutination method used to detect Streptococcus-O-lysine antibodies had a qualitative and quantitative test result of 33.3% in sample 31, while in sample 32, the quantitative test result was 66.7%. The overall pass rate of Streptococcus-O-lysine antibody detection was 100%, while the overall pass rate of streptodornase detection was between 33.3% and 100%.</Pgraph><SubHeadline>3.13 Rheumatoid factor (323)</SubHeadline><SubHeadline2>3.13.1 Sample information</SubHeadline2><Pgraph>Samples 31 and 32 were taken from clinically healthy blood donors.</Pgraph><SubHeadline2>3.13.2 Determination of the target values</SubHeadline2><Pgraph>The mode of the results of the reference laboratories was set as the target value for the qualitative test results, while in the case of the semi-quantitative test results, the robust mean of all participants was established as the target value <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are indicated in <TextGroup><PlainText>Table 13 </PlainText></TextGroup><ImgLink imgNo="13" imgType="table"/>.</Pgraph><SubHeadline2>3.13.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>The qualitative test results for both samples for all methods were 100%. The qualitative and quantitative test results for sample 31 for method 1 was 50%, while the quantitative test result for sample 32 for method 1 was 50%.</Pgraph><SubHeadline>3.14 Mycoplasma pneumonia antibodies (324)</SubHeadline><SubHeadline2>3.14.1 Sample information</SubHeadline2><Pgraph>Samples 61 and 62 originated from patients with several known respiratory infections in their recent medical history.</Pgraph><SubHeadline2>3.14.2 Determination of the target values</SubHeadline2><Pgraph>The mode of the results for all participants was set as the target value for the qualitative and semi-quantitative test results <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are presented in <TextGroup><PlainText>Table 14 </PlainText></TextGroup><ImgLink imgNo="14" imgType="table"/>.</Pgraph><SubHeadline2>3.14.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>Evidence of an infection with <Mark2>M. pneumonia</Mark2> was detected in both samples. In both samples both the reference laboratories and most participants found variable results and weak IgG and IgA seroreactivity <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The pass rat<TextGroup><PlainText>e f</PlainText></TextGroup>or the overall diagnostic results was 100% for sampl<TextGroup><PlainText>e 6</PlainText></TextGroup>1 and 82.7% for sample 62.</Pgraph><SubHeadline>3.15 Coxiella burnetii antibodies (325)</SubHeadline><SubHeadline2>3.15.1 Sample information</SubHeadline2><Pgraph>Sample 61 was donated by a healthy blood donor who showed no evidence of a recent infection. Sample 62 was donated by a patient a few months after having acute <Mark2>C. burnetii</Mark2> pneumonia.</Pgraph><SubHeadline2>3.15.2 Determination of the target values</SubHeadline2><Pgraph>The mode of the results of the reference laboratories was set as the target value for the qualitative test results, while the mode of the results of all participants was set as the target value for the semi-quantitative test results <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are shown in Table 15 <ImgLink imgNo="15" imgType="table"/>.</Pgraph><SubHeadline2>3.15.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>Sample 61 tested negative for <Mark2>C. burnetii</Mark2>, while sampl<TextGroup><PlainText>e 6</PlainText></TextGroup>2 tested positive. Sample 61 exhibited IgG phase I IFT titers of 5120 (median), IgG phase II IFT titers of 2560 (median) as well as weakly reactive IgM and IgA results. These results suggested a relatively recent case of pneumonia. Most participants and expert laboratories made variable clinical comments as to whether the test constellation should be interpreted as an acute or chronic <Mark2>Coxiella</Mark2> infection <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>.</Pgraph><Pgraph>The pass rate for the overall diagnostic results of sampl<TextGroup><PlainText>e 6</PlainText></TextGroup>1 was 100%, while the pass rate of sample 62 wa<TextGroup><PlainText>s 8</PlainText></TextGroup>9.0%.</Pgraph><SubHeadline>3.16 Salmonella antibodies (331)</SubHeadline><SubHeadline2>3.16.1 Sample information</SubHeadline2><Pgraph>Samples 31, 32, 61 and 62 originated from clinically healthy blood donors.</Pgraph><SubHeadline2>3.16.2 Determination of the target values</SubHeadline2><Pgraph>The mode of the results of the reference laboratories was set as the target value for the qualitative test results, while the results of the reference laboratories were stipulated as the target value of the semi-quantitative results <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are listed in Table 16 <ImgLink imgNo="16" imgType="table"/>.</Pgraph><SubHeadline2>3.16.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>No evidence of a <Mark2>Salmonella</Mark2> infection was detected in all samples. The pass rates for all samples for the overall diagnostic results were between 94.4% and 98.4%.</Pgraph><SubHeadline>3.17 Borrelia burgdorferi antibodies (332)</SubHeadline><SubHeadline2>3.17.1 Sample information</SubHeadline2><Pgraph>Samples 31 and 61 originated from a healthy blood donor without evidence of a tick bite or clinical Lyme borreliosis in his medical history. Sample 32 was donated by a patient with past Lyme arthritis treated several years ago and confirmed by culture and PCR. Sample 62 was donated two years after the infection by a patient with successfully treated Lyme arthritis.</Pgraph><SubHeadline2>3.17.2 Determination of the target values</SubHeadline2><Pgraph>The mode of the results of the reference laboratories was set as the target value for the qualitative test results <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The results are listed in Table 17 <ImgLink imgNo="17" imgType="table"/>.</Pgraph><SubHeadline2>3.17.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>No evidence of an infection with <Mark2>B. burgdorferi</Mark2> was dete<TextGroup><PlainText>cted i</PlainText></TextGroup>n samples 31 and 61, while pathogens were dete<TextGroup><PlainText>cted i</PlainText></TextGroup>n samples 32 and 62, indicating an infection with <Mark2>B</Mark2><TextGroup><Mark2>. b</Mark2></TextGroup><Mark2>urgdorferi</Mark2>. Samples 32 and 62 showed high IgG antibody titers together with borderline reactive IgM test results, suggesting a late phase of the borrelia-specific immune response. Figure 4 <ImgLink imgNo="4" imgType="figure"/> and Figure 5 <ImgLink imgNo="5" imgType="figure"/> show the distribution of specific IgG and IgM borrelia immunoblot bands for sample 32 <TextLink reference="7"></TextLink>, <TextLink reference="8"></TextLink>. The distribution of the immunoblot bands reported for the positive sample 62 is depicted in Figure 6 <ImgLink imgNo="6" imgType="figure"/>.</Pgraph><Pgraph>The pass rates for the overall diagnostic results of the negative samples 31 and 61 were between 98.2% and 98.7%, while for the positive samples 32 and 62 they were between 82.5% and 94.8%.</Pgraph><SubHeadline>3.18 Helicobacter pylori antibodies (334)</SubHeadline><SubHeadline2>3.18.1 Sample information</SubHeadline2><Pgraph>Samples 31, 32 and 61 originated from clinically healthy blood donors. Sample 62 was taken from a helicobacter-positive patient shortly after finishing eradication therapy.</Pgraph><SubHeadline2>3.18.2 Determination of the target values</SubHeadline2><Pgraph>The mode of the results of the reference laboratories was set as the target value for the qualitative test results. The results are shown in Table 18 <ImgLink imgNo="18" imgType="table"/>.</Pgraph><SubHeadline2>3.18.3 Overall diagnostic interpretation and commentary on the test results</SubHeadline2><Pgraph>There was no evidence of an infection with <Mark2>H. pylori</Mark2> in samples 32 and 61. Samples 31 and 62 showed positive IgG and IgA antibody reactivity by ELISA and immunoblot, indicating an infection or colonization with <Mark2>H. pylori</Mark2>. In sample 61, the qualitative result for IgA blot was 60%, while for IgG blot it was 71.4%. The pass rates for the overall diagnostic results of the positive samples 31 an<TextGroup><PlainText>d 6</PlainText></TextGroup>2 were between 91.3% and 93.0%, while for the negative samples 61 and 32 they were between 82.5% and 95.7%.</Pgraph></TextBlock>
<TextBlock linked="yes" name="4 Discussion and conclusion">
<MainHeadline>4 Discussion and conclusion</MainHeadline><Pgraph>EQA can be used as a tool in improving diagnostic processes in laboratories. It leads to more reliable and prompt diagnostic results, which sustain the quality and efficiency of patient care. The results of the EQA presented in this report generally show moderate to very good diagnostic quality. However, some special comments on serology need to be made:</Pgraph><Pgraph>Regarding the <Mark2>Treponema pallidum</Mark2> serology (311), sample 31 had low pass rates of 66.7% for the qualitative detection of IgM antibodies by immunoblot and 73.9% for the detection of IgG antibodies by FTA-ABS. These contributed to the poor overall pass rate of 77.2% for all test methods. Generally, laboratory results in 2017 showed better pass rates compared to the results in 2016. In the case of <Mark2>Chlamydia trachomatis</Mark2> serology (312), the overall pass rate was between 50% and 100% for all tests in sample 31. A pass rate of 50% was observed for the qualitative detection of IgG antibodies by immunoblot. Next, pass rates of 50.9% and 63.6% were observed for the qualitative detection of IgG and IgM a<TextGroup><PlainText>ntibodi</PlainText></TextGroup>es respectively, both detected by ELISA in the above-mentioned sample. In sample 61, the lowest pass rate of 50% was observed for the qualitative detection of IgG antibodies by immunoblot, while in sample 62 the lowest pass rate was 75% for the same method. With regard to <Mark2>Chlamydia pneumonia</Mark2> serology (314), the overall pass rate was between 64.7% and 100% for all tests in sample 31. A pass rate of 66.7% was observed for the qualitative detection and 64.7% for the quantitative detection of IgM antibodies by MIFT. A pass rate of 77.8% was observed for the qualitative detection of IgA antibodies, also by MIFT, and a pass rate of 66.7% was recorded for the qualitative detection of IgG antibodies by immunoblot in the above-mentioned sample. In sampl<TextGroup><PlainText>e 3</PlainText></TextGroup>2, the lowest pass rate of 77.8% was observed for the qualitative detection of IgM antibodies by MIFT. Generally, the pass rates were lower in 2017 compared to the results in 2016. In the case of <Mark2>Yersinia</Mark2> antibody serology (315), the lowest pass rate of 76.9% was observed for the qualitative detection of IgG antibodies by immunoblot in sample 31. Sample 32 recorded the lowest pass rate of 70% for the qualitative detection of IgM antibodies by immunoblot. In the case of <Mark2>Campylobacter</Mark2> serology (319), the lowest pass rate of 64.7% was observed for qualitative and 72.2% for quantitative detection by CFT in sample 31. In the same sample, a pass rate of 75% was detected for the qualitative detection of IgA by immunoblot. Sample 32 recorded the lowest pass rate of 75% for the qualitative detection of IgG antibodies by immunoblot. With respect to <Mark2>Streptococci</Mark2> serology (321), the pass rate was 33.3% for qualitative and quantitative detection by latex agglutination in sample 31, while in sample 32, a pass rate of 66.7% for quantitative detection by latex agglutination was observed. Generally, the pass rates were lower in 2017 than in 2016. Regarding rheumatoid factor serology (323), the pass rate was 50% for qualitative and quantitative detection using the nephelometry method in sample 31, while a pass rate of 50% for quantitative detection by the same method mentioned above was observed in sample 32. With regard to <Mark2>Mycoplasma pneumonia</Mark2> serology (324), the pass rate was 63.6% and 66.7% for qualitative and quantitative detection respectively, using PHA in sample 62. In the same sample, the pass rate was 68.9% for the quantitative detection of IgA antibodies by ELISA. With respect to the <Mark2>Coxiella burnetii</Mark2> serology (325), the overall pass rate was 100% in the diagnostic assessment of sample 61. The lowest pass rate for quantitative detection of IgA by IFT was 63.6%, showing poorer laboratory results than the pass rate in 2016. In the case of the <Mark2>Borrelia burgdor</Mark2><TextGroup><Mark2>fer</Mark2></TextGroup><Mark2>i</Mark2> serology (332), both samples 31 and 32 showed the lowest pass rate of 75% in the qualitative detection by line immunoblot. In the diagnostic assessment of sample 31, an overall pass rate of 98.2% was recorded, while in sample 32, it was 82.5%. In the <Mark2>Helicobacter pylori</Mark2> serology (334), the overall pass rate for sample 61 was between 60% and 100%. In terms of the qualitative result, the pass rate was 71.4% for IgG detection and 60% for IgA detection, both by immunoblot.</Pgraph><Pgraph>The above-mentioned findings and comments show, as in previous years, the need for further improvement in certain diagnostic procedures. This will achieve more standardized and higher quality testing in Germany to ensure even better diagnostic test results in the routine clinical setting. This will maintain quality and efficiency in patient care.</Pgraph></TextBlock>
<TextBlock linked="yes" name="Notes">
<MainHeadline>Notes</MainHeadline><SubHeadline>Competing interests</SubHeadline><Pgraph>The authors declare that they have no competing interests.</Pgraph></TextBlock>
<References linked="yes">
<Reference refNo="1">
<RefAuthor>Murray PR</RefAuthor>
<RefTitle>The clinician and the Microbiology Laboratory</RefTitle>
<RefYear>2015</RefYear>
<RefBookTitle>Mandell, Douglas and Bennett’s Principles and Practice of Infectious Diseases</RefBookTitle>
<RefPage>191-223</RefPage>
<RefTotal>Murray PR. The clinician and the Microbiology Laboratory. In: Bennett JE, Dolin R, Blaser MJ, editors. Mandell, Douglas and Bennett’s Principles and Practice of Infectious Diseases. 8th Ed. Philadelphia: Elsevier Saunders; 2015. p. 191-223.</RefTotal>
</Reference>
<Reference refNo="2">
<RefAuthor>Smit R</RefAuthor>
<RefAuthor>Hunfeld KP</RefAuthor>
<RefTitle>Quality of bacteriological infection serology in Germany: analysis of the 2016 proficiency testing trials</RefTitle>
<RefYear>2020</RefYear>
<RefJournal>GMS Z Forder Qualitatssich Med Lab</RefJournal>
<RefPage>Doc04</RefPage>
<RefTotal>Smit R, Hunfeld KP. Quality of bacteriological infection serology in Germany: analysis of the 2016 proficiency testing trials. GMS Z Forder Qualitatssich Med Lab. 2020;11:Doc04. DOI: 10.3205/lab000039</RefTotal>
<RefLink>https://doi.org/10.3205/lab000039</RefLink>
</Reference>
<Reference refNo="3">
<RefAuthor>Wellinghausen N</RefAuthor>
<RefAuthor>Abele-Horn M</RefAuthor>
<RefAuthor>Donoso Mantke O</RefAuthor>
<RefAuthor>Enders M</RefAuthor>
<RefAuthor>Fingerle V</RefAuthor>
<RefAuthor>Gärtner B</RefAuthor>
<RefAuthor>Hagedorn J</RefAuthor>
<RefAuthor>Rabenau HF</RefAuthor>
<RefAuthor>Reiter-Owona I</RefAuthor>
<RefAuthor>Tintelnot K</RefAuthor>
<RefAuthor>Weig M</RefAuthor>
<RefAuthor>Zeichhardt H</RefAuthor>
<RefAuthor>Hunfeld KP</RefAuthor>
<RefTitle></RefTitle>
<RefYear>2016</RefYear>
<RefBookTitle>MiQ 35a–c Qualitätsstandards in der mikrobiologisch-infektiologischen Diagnostik: Infektionsimmunologische Methoden Teil 1–3</RefBookTitle>
<RefPage></RefPage>
<RefTotal>Wellinghausen N, Abele-Horn M, Donoso Mantke O, Enders M, Fingerle V, Gärtner B, Hagedorn J, Rabenau HF, Reiter-Owona I, Tintelnot K, Weig M, Zeichhardt H, Hunfeld KP. MiQ 35a–c Qualitätsstandards in der mikrobiologisch-infektiologischen Diagnostik: Infektionsimmunologische Methoden Teil 1–3. München, Jena: Urban & Fischer; 2016.</RefTotal>
</Reference>
<Reference refNo="4">
<RefAuthor>World Health Organization</RefAuthor>
<RefAuthor> Clinical and Laboratory Standards Institute</RefAuthor>
<RefAuthor> Centers for Disease Control and Prevention</RefAuthor>
<RefTitle></RefTitle>
<RefYear>2009</RefYear>
<RefBookTitle>Laboratory Quality Management System Training Toolkit – Current Laboratory Practice Series. Module 10: Assessment – External Quality Assessment (EQA)</RefBookTitle>
<RefPage></RefPage>
<RefTotal>World Health Organization; Clinical and Laboratory Standards Institute; Centers for Disease Control and Prevention. Laboratory Quality Management System Training Toolkit – Current Laboratory Practice Series. Module 10: Assessment – External Quality Assessment (EQA). Lyon, Wayne: WHO, CDC, CLSI; 2009. Available from: https://www.who.int/ihr/training/laboratory_quality/10_b_eqa_contents.pdf</RefTotal>
<RefLink>https://www.who.int/ihr/training/laboratory_quality/10_b_eqa_contents.pdf</RefLink>
</Reference>
<Reference refNo="5">
<RefAuthor>Müller I</RefAuthor>
<RefAuthor>Hunfeld KP</RefAuthor>
<RefTitle></RefTitle>
<RefYear>2017</RefYear>
<RefBookTitle>Manual June 2017. Testing Information Bacteriology Infection Serology DAkkS. D-EP-15027-02-00 – June 2017</RefBookTitle>
<RefPage></RefPage>
<RefTotal>Müller I, Hunfeld KP. Manual June 2017. Testing Information Bacteriology Infection Serology DAkkS. D-EP-15027-02-00 – June 2017. Düsseldorf: INSTAND e.V.; 2017 [last accessed 2020 Mar 12]. Available from: https://www.instand-ev.de/System/rv-files/Manual_Bacteriology%20Infection%20Serology%20June%202017.pdf</RefTotal>
<RefLink>https://www.instand-ev.de/System/rv-files/Manual_Bacteriology%20Infection%20Serology%20June%202017.pdf</RefLink>
</Reference>
<Reference refNo="6">
<RefAuthor>Müller I</RefAuthor>
<RefAuthor>Hunfeld KP</RefAuthor>
<RefTitle></RefTitle>
<RefYear>2017</RefYear>
<RefBookTitle>Manual November 2017 Testing Information Bacteriology Infection Serology DAkkS. D-EP-15027-02-00 – November 2017</RefBookTitle>
<RefPage></RefPage>
<RefTotal>Müller I, Hunfeld KP. Manual November 2017 Testing Information Bacteriology Infection Serology DAkkS. D-EP-15027-02-00 – November 2017. Düsseldorf: INSTAND e.V.; 2017 [last accessed 2020 Mar 12]. Available from: https://www.instand-ev.de/System/rv-files/Manual_Bacteriology%20Infection%20Serology_Nov'17.pdf</RefTotal>
<RefLink>https://www.instand-ev.de/System/rv-files/Manual_Bacteriology%20Infection%20Serology_Nov'17.pdf</RefLink>
</Reference>
<Reference refNo="7">
<RefAuthor>Müller I</RefAuthor>
<RefAuthor>Hunfeld KP</RefAuthor>
<RefTitle></RefTitle>
<RefYear>2017</RefYear>
<RefBookTitle>Report on INSTAND e.V. EQAS 310-334 – June 2017</RefBookTitle>
<RefPage></RefPage>
<RefTotal>Müller I, Hunfeld KP. Report on INSTAND e.V. EQAS 310-334 – June 2017. Düsseldorf: INSTAND e.V.; 2017 [last accessed 2020 Jan 12]. Available from: https://www.instand-ev.de/System/rv-files/1703_RV_310-334_en.pdf</RefTotal>
<RefLink>https://www.instand-ev.de/System/rv-files/1703_RV_310-334_en.pdf</RefLink>
</Reference>
<Reference refNo="8">
<RefAuthor>Müller I</RefAuthor>
<RefAuthor>Hunfeld KP</RefAuthor>
<RefTitle></RefTitle>
<RefYear>2017</RefYear>
<RefBookTitle>Report on INSTAND e.V. EQAS 310-334 – November 2017</RefBookTitle>
<RefPage></RefPage>
<RefTotal>Müller I, Hunfeld KP. Report on INSTAND e.V. EQAS 310-334 – November 2017. Düsseldorf: INSTAND e.V.; 2017 [last accessed 2020 Jan 12]. Available from: https://www.instand-ev.de/System/rv-files/1706_RV_310-334_en-End.pdf</RefTotal>
<RefLink>https://www.instand-ev.de/System/rv-files/1706_RV_310-334_en-End.pdf</RefLink>
</Reference>
</References>
<Media>
<Tables>
<Table format="png">
<MediaNo>1</MediaNo>
<MediaID>1</MediaID>
<Caption><Pgraph><Mark1>Table 1: Study groups and the number of participants included in two proficiency testing trials in Germany, 2017</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>2</MediaNo>
<MediaID>2</MediaID>
<Caption><Pgraph><Mark1>Table 2: Tetanus toxoid detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>3</MediaNo>
<MediaID>3</MediaID>
<Caption><Pgraph><Mark1>Table 3: Treponema pallidum antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>4</MediaNo>
<MediaID>4</MediaID>
<Caption><Pgraph><Mark1>Table 4: Chlamydia trachomatis antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>5</MediaNo>
<MediaID>5</MediaID>
<Caption><Pgraph><Mark1>Table 5: Chlamydia trachomatis antibody direct detection by ELISA/PCR during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>6</MediaNo>
<MediaID>6</MediaID>
<Caption><Pgraph><Mark1>Table 6: Chlamydia pneumonia antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>7</MediaNo>
<MediaID>7</MediaID>
<Caption><Pgraph><Mark1>Table 7: Yersinia antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>8</MediaNo>
<MediaID>8</MediaID>
<Caption><Pgraph><Mark1>Table 8: Bordetella pertussis antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>9</MediaNo>
<MediaID>9</MediaID>
<Caption><Pgraph><Mark1>Table 9: Diphtheria toxoid antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>10</MediaNo>
<MediaID>10</MediaID>
<Caption><Pgraph><Mark1>Table 10: Campylobacter antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>11</MediaNo>
<MediaID>11</MediaID>
<Caption><Pgraph><Mark1>Table 11: Procalcitonin detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>12</MediaNo>
<MediaID>12</MediaID>
<Caption><Pgraph><Mark1>Table 12: Streptococci antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>13</MediaNo>
<MediaID>13</MediaID>
<Caption><Pgraph><Mark1>Table 13: Rheumatoid factor detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>14</MediaNo>
<MediaID>14</MediaID>
<Caption><Pgraph><Mark1>Table 14: Mycoplasma pneumonia antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>15</MediaNo>
<MediaID>15</MediaID>
<Caption><Pgraph><Mark1>Table 15: Coxiella burnetii antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>16</MediaNo>
<MediaID>16</MediaID>
<Caption><Pgraph><Mark1>Table 16: Salmonella antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>17</MediaNo>
<MediaID>17</MediaID>
<Caption><Pgraph><Mark1>Table 17: Borrelia burgdorferi antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<Table format="png">
<MediaNo>18</MediaNo>
<MediaID>18</MediaID>
<Caption><Pgraph><Mark1>Table 18: Helicobacter pylori antibody detection during the 2017 proficiency testing trials</Mark1></Pgraph></Caption>
</Table>
<NoOfTables>18</NoOfTables>
</Tables>
<Figures>
<Figure format="png" height="406" width="606">
<MediaNo>1</MediaNo>
<MediaID>1</MediaID>
<Caption><Pgraph><Mark1>Figure 1: The distribution of the immunoblot bands reported for the positive sample 31 [7], [8]; recovery rate (%) of the submitted IgG immunoblot bands for sample 311/31 (May 2017), participants N=151</Mark1></Pgraph></Caption>
</Figure>
<Figure format="png" height="397" width="589">
<MediaNo>2</MediaNo>
<MediaID>2</MediaID>
<Caption><Pgraph><Mark1>Figure 2: The distribution of the immunoblot bands reported for the positive sample 31 [7], [8]; recovery rate (%) of the submitted IgM immunoblot bands for sample 311/31 (May 2017), participants N=103</Mark1></Pgraph></Caption>
</Figure>
<Figure format="png" height="326" width="788">
<MediaNo>3</MediaNo>
<MediaID>3</MediaID>
<Caption><Pgraph><Mark1>Figure 3: The distribution of the immunoblot bands reported for the positive sample 61 [7], [8]; recovery rate (%) of the submitted IgG immunoblot bands for sample 311/61 (Nov. 2017), participants N=130</Mark1></Pgraph></Caption>
</Figure>
<Figure format="png" height="372" width="734">
<MediaNo>4</MediaNo>
<MediaID>4</MediaID>
<Caption><Pgraph><Mark1>Figure 4: The distribution of the immunoblot bands reported for sample 32 [7], [8]; recovery rate (%) of the submitted IgG immunoblot bands for sample 332/32 (May 2017), participants N=314</Mark1></Pgraph></Caption>
</Figure>
<Figure format="png" height="370" width="733">
<MediaNo>5</MediaNo>
<MediaID>5</MediaID>
<Caption><Pgraph><Mark1>Figure 5: The distribution of the immunoblot bands reported for sample 32 [7], [8]; recovery rate (%) of the submitted IgM immunoblot bands for sample 332/32 (May 2017), participants N=285</Mark1></Pgraph></Caption>
</Figure>
<Figure format="png" height="395" width="773">
<MediaNo>6</MediaNo>
<MediaID>6</MediaID>
<Caption><Pgraph><Mark1>Figure 6: The distribution of the immunoblot bands reported for sample 62 [7], [8]; recovery rate (%) of the submitted IgG immunoblot bands for sample 332/62 (Nov 2017), participants N=284</Mark1></Pgraph></Caption>
</Figure>
<NoOfPictures>6</NoOfPictures>
</Figures>
<InlineFigures>
<NoOfPictures>0</NoOfPictures>
</InlineFigures>
<Attachments>
<NoOfAttachments>0</NoOfAttachments>
</Attachments>
</Media>
</OrigData>
</GmsArticle>]]></plaintext></textgroup></pgraph></textblock></origdata></gmsarticle>