Autoantibody to NA14 is an independent marker primarily for Sjogren's syndrome

Nuclear Autoantigen of 14 kDa (NA14) was originally identified using the serum of a Sjögren's syndrome (SS) patient as probe in screening a human testis cDNA expression library. To date there is no report in the systematic analysis of the prevalence of autoantibodies to NA14. In this study, anti-NA14 was determined in several rheumatic diseases from independent cohorts in the US and Japan. The prevalence of anti-NA14 were 18/132 (13.6%) in primary SS, 0/50 (0%) secondary SS, 2/100 (2%) SLE, 1/43 (2.3%) scleroderma, 0/54 (0%) rheumatoid arthritis, 1/29 (3.4%) polymyositis/dermatomyositis, and 0/58 (0%) normal healthy controls. The frequencies of anti-NA14 positive sera in primary SS are statistically greater than normal healthy controls (p=0.006), secondary SS (p=0.044), and other rheumatic diseases. Furthermore, among 11 anti-NA14 positive primary SS sera, 4/11 (36.3%) sera were negative for both anti-SS-A/Ro and SS-B/La antibodies. Thus anti-NA14 autoantibodies may be useful for the discrimination of primary versus secondary SS and serve as a diagnostic marker for primary SS especially in seronegative (anti-SS-A/Ro and anti-SS-B/La antibodies negative) patients with SS.