A new study published in the Journal of Clinical Laboratory Analysis explored antinuclear antibody (ANA) positivity rate, titers and patterns in patients with systemic autoimmune rheumatic diseases (SARD), including systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), primary Sjögrens syndrome (pSS), systemic sclerosis (SSc) and mixed connective tissue disease (MCTD), compared with healthy controls (HC).

In this study, assess antinuclear antibody titers and patterns were retrospectively identified and compared by indirect immunofluorescence assay (IIFA) using human epithelial cells (HEp-2) and primate liver tissue substrate, according to international consensus in SARD. Serum complement 3 (C3), C4 and immunoglobulin G were compared among subgroups with different ANA titers.

The results founda total of 3 510 samples, including 2034 SLE, 973 RA, 155 SSc, 309 pSS, and 39 MCTD cases. There was no difference in age between HC and SARD, excluding RA. While the ANA positivity rate in SARD and HC was 78.7% and 12.2%, respectively. A titer of ≥1:320 revealed a positive predictive value(PPV) of 84.0% in SARD. SLE patients with ANA titers ≥1:320 had significantly lower levels of C3 and C4. AC-4 (31.2%) was the major pattern in patients with SARD, followed by AC-5 (23.9%) and AC-1 (18.8%). In addition, SLE mostly presented with AC-4 (30.3%). Several mixed patterns provided a significant hint for SSc and SLE. The major pattern in HC was AC-2 (12.2%).

In inference, it was stated that assess antinuclear antibody positivity, titers and patterns elicit differences in various SARD, contributing to the classification of SARD.

Source: Journal of Clinical Laboratory Analysis. 2020 Oct 13;e23546. doi: 10.1002/jcla.23546.