Limitations of antinuclear antibody tests (HEp-2) are overcome with the autoimmune target test (IT-1) in systemic lupus erythematosus.

摘要

Controversy concerning the antinuclear antibody (ANA)-positive rates in patients with systemic lupus erythematous (SLE) has persisted, and many efforts in improving the test quality have been made. After reading the article "Abnormal ANA titers are less common than generally assumed in established cases of SLE" by Sjowall, et at, we would like to express our opinion. In this article, the 95th percentile titer (women 1:200, men 1:80) of healthy blood donors was chosen as the standard in determining the cutoff titer for the ANA test in patients with SLE. As a result, the article reported a fluorescent ANA-positive rate in patients with established SLE as 76%, and it focused on its result of a lower positive rate. However, this finding may result in misunderstanding, by leading investigators to accept a much lower ANA-positive rate than what had been previously reported. Further, it has a potential threat in questioning the basic pathogenesis of SLE, which is destined to possess ANA. Looking at the data from this article, the positive rates were low even when the cutoff titers were similar to the conventional screening titers (84% in 1:50,80% in 1:100), and the positive rate in healthy blood donors at 1:40 dilution level was as high as 45%. Looking at all these aspects, it would be more reasonable to think that the problem lies with the limitation of the HEp-2 cell line in detecting autoan-tibody in patients with established SLE than to merely conclude that abnormal ANA titers are less common. These limitations have been recognized in many studies testing the HEp-2 cell line. It would also be hard to deny that such limitations have troubled many investigators in interpreting then-data.