IL17A and systemic lupus erythematosus: However, the results showed that the correlation between the circulating IL-17 level and SLE activity was slightly stronger when circulating IL-17 was measured by ELISA (Fisher z = 0.41; Z = 5.029, P < 0.001) than by non-ELISA (Fisher z = 0.40; Z = 2.200, P = 0.028), although no statistically significant difference was found between groups (P = 0.810).