Objectives: Diagnosis of Systemic Autoimmune Rheumatic Diseases using antinuclear autoantibodies (ANA) is dependent on many factors and varies between populations, such that the screening dilution used for indirect immunofluorescence assay (IIFA) should be defined locally for each population. The aim of the study was firstly, to assess the prevalence of ANA in the Polish adult population depending on age, sex and the cut-off threshold used for the results obtained. Second, we estimated the occurrence of individual types of ANA staining patterns.
Methods: The tested material included serum samples from 1731 participants (1043 women and 688 men) that were tested with the commercially available IIFA using two cut-off thresholds 1:100 and 1:160.
Results: We found ANA in 260 participants (15.0%), but the percentage of positive results strongly depended on the cut-off level. For a cut-off threshold 1:100, the positive population was 19.5% and for the 1:160 cut-off threshold, it was 11.7%. The most prevalent ANA staining pattern was AC-2 Dense Fine speckled (50%), followed by AC-21 Reticular/AMA (14.38%) ANA were more common in women (72%); 64% of ANA positive patients were over 50 years of age.
Conclusion: ANA prevalence in the Polish population is at a level observed in other highly developed countries. ANA were more prevalent in women and elderly individuals. In order to reduce the number of positive results released, we suggest that Polish laboratories should set 1:160 as the cut-off threshold.