To determine probability of finding antinuclear antibodies (ANA) and anti extractable nuclear antigens (ENA) positive samples and associating ANA patterns with anti-ENA reactivities among a consecutive cohort of samples of systemic rheumatic disease patients referred for ANA testing.
Prospective cohort study.
Immunology Department, Armed Forces Institute of Pathology, Rawalpindi, Pakistan, from January to June 2016.
All the samples referred for ANA testing with clinical suspicion of systemic rheumatic disease were included. After screening, ANA positive samples were subjected to anti-ENA antibodies testing (including anti-SSA, antiSSB, anti-Sm, anti-RNP, anti-SCL-70 and anti-Jo-1 antibodies) and ANA pattern and titer determination.
Of 4,347 samples received, 397 were positive for ANA (9%). Of 397, 96 (24%) samples positive on ENA screen were tested for anti-ENA reactivity. Anti-SSA antibodies were found in 59 samples. Commonest ANA patterns were coarse and fine speckled (43 and 22 samples of 81 tested), while majority of samples carried ANA in titers of 1:40 and 1:80 (22 and 18 samples of 81 tested). No specific ANA pattern was associated with any particular anti-ENA reactivity.
Among samples/patients referred for investigations of autoimmune disorders, probability of finding positive ANA is approximately 9%. Of these 9%, about 24% also show reactivity against ENA. Commonest ANA pattern is coarse speckled and majority of such patients carry ANA in titers ranging from 1:40 to 1:80. Commonest ENA reactivity was against SSA.