A Multicenter Analysis of Subjectivity of Indirect Immunofluorescence Test in Antinuclear Antibody Screening
Vildan TURAN FARAŞAT1, Talat ECEMİŞ1, Yavuz DOĞAN2, Aslı Gamze ŞENER3, Gülfem TEREK ECE4, Pınar Erbay DÜNDAR5, Tamer ŞANLIDAĞ6
1Department of Medical Microbiology, Manisa Celal Bayar University, Faculty of Medicine, Manisa, Turkey
2Department of Medical Microbiology, Dokuz Eylül University, Faculty of Medicine, Izmir, Turkey
3Department of Medical Microbiology, Katip Çelebi University, Faculty of Medicine, Izmir, Turkey
4Department of Medical Microbiology, Izmir Medicalpark Hospital, Izmir, Turkey
5Department of Public Health, Manisa Celal Bayar University, Faculty of Medicine, Manisa, Turkey
6Department of Medical Microbiology, Manisa Celal Bayar University, Faculty of Medicine, Manisa, Turkey
Keywords: Antinuclear antibodies, autoimmune rheumatic diseases, indirect immunofluorescence, subjectivity
Objectives: This study aims to evaluate the interpretation of the antinuclear antibody (ANA)-indirect immunofluorescence (IIF) test results based on the interpreter-related subjectivity and to examine the inter-center agreement rates with the performance of each laboratory.
Patients and methods: The ANA-IIF testing was carried out in a total of 600 sera and evaluated by four laboratories. The inter-center agreement rates were detected. The same results given by the four centers were accepted as gold standard and the predictive values of each center were calculated.
Results: The inter-center agreement was reported for ANA-IIF test results from 392 of 600 (65.3%) sera, while 154 of 392 results were positive. Four study centers reported 213 (35.5%), 222 (37.0%), 266 (44.3%), and 361 (60.2%) positive test results, respectively. In terms of the patterns, the highest and lowest positive predictive values were 72.3% and 42.7%, respectively, while the highest and lowest negative predictive values were 99.6% and 61.5%, respectively. The agreement for semi-quantitative evaluation at three levels of fluorescence intensity stated by four centers was detected in 100 sera at 87% 3(+), while the other two levels were 6% and 7%. The highest predictive value for the highest fluorescence intensity of 3(+) was found to be 71.9%.
Conclusion: Significant differences may be observed among laboratories in terms of qualitative results, patterns, and semi-quantitative determination of the fluorescence intensity in the ANA-IIF testing, particularly at low fluorescence intensity levels and in those with speckled patterns. In case of any discrepancy between ANA-IIF test and clinical prediagnosis, the test should be repeated in another laboratory, if necessary.