Reliability and sensitivity of diagnostic tests for primary Sjogren's syndrome

Objective. To investigate whether diagnostic tests for primary Sjogren's sy ndrome (pSS) are reproducible when repeated after one year (reliability). T o evaluate whether the sensitivity of the diagnostic tests increases with r epeated testing. Methods. A structured interview investigating the subjective sensation of d ry eyes and dry mouth, and the diagnostic tests Schirmer L unstimulated who le saliva collection (UWSC), serological tests for antinuclear antibodies ( ANA), for anti-Ro/SSA and anti-La/SSB antibodies as well as Waaler's test f or rheumatoid factor, were performed twice with a one year interval in 66 p atients with pSS. Reliability was given as the percentage of positive tests remaining positive at the second examination, while sensitivity was given as the percentage of patients with positive tests. Results, Highest reliability was obtained for the sensation of dry mouth (9 8.2%) and sensation of dry eyes (96.4%), and anti-SSA/SSB antibodies (93.3% ). Lowest reliability was obtained for rheumatoid factor at cutoff titer 1: 32 (70.6%) and positive Schirmer I in one eye (77.4%). The reliability for ANA was 80% at cutoff titer 1:32, and increased to 93.3% at cutoff titer 1: 128. UWSC had a reliability of 84.2%. The pooled sensitivity for all the te sts increased significantly (p < 0.05) compared to the examination, which h ad the lowest sensitivity. Conclusion. The diagnostic tests for pSS are generally highly reliable when performed twice with a one year interval. The gain in sensitivity by repea ting the tests is limited. being most marked for Schirmer I.