Antinuclear antibodies measured by enzyme immunoassay in patients with systemic lupus erythematosus: relation to disease activity

To evaluate the correlation between measurements of antinuclear antibodies serum levels by enzyme immunoassay (ANA-EIA), and the degree of systemic lupus erythematosus disease activity. To retest the performance of the test compared to measurement of antinuclear antibodies by immunofluorescence (ANA-IIF). Eighty-five sera from 71 patients with SLE were tested. Demographic, clinical, laboratory, and SLEDAI status were collected. The sera were tested for ANA-EIA and by ANA-IIF at 1:40 and 1:160 dilutions. Serum levels of ANA-EIA were compared to the overall SLEDAI score and to each of its components. A SLEDAI score of >= 6 was considered clinically significant. The sera of fifty-one healthy volunteers served as controls. Serum levels of ANA-EIA were significantly higher in patients with a SLEDAI score of >= 6 compared to the group of patients with a SLEDAI score of < 6 (P = 0.004). High serum levels of ANA-EIA correlated significantly with elevated anti DS-DNA antibodies (P < 0.001), low C-3 or C-4 levels (P < 0.001), pyuria (P < 0.011), arthritis (P = 0.019), and new rash (P = 0.019). Levels of ANA-EIA were significantly higher in patients tested positive by IIF compared to those who tested negative. Higher serum levels of ANA-EIA correlated with clinically significant disease activity in patients with SLE. Higher serum levels of ANA-EIA also correlated with some single items of the SLEDAI. The results also reiterated the validity of ANA-EIA testing in patients with SLE. Further longitudinal studies are needed in order to test the hypothesis that serum ANA-EIA levels might reflect fluctuations in disease activity.