Background ANA – heterogeneous group of autoantibodies, reacting with the different components of nucleus and cytoplasm. ANA is main serological marker SLE and others systemic autoimmune rheumatic diseases (SARDs). The implementation of new highly productive methods of immune analysis with the use of automated systems into clinical practice creates the preconditions for standardization and improvement of reproducibility of ANA determination.
Objectives To compare the diagnostic value of automated methods of ANA determination (IIF-HEp-2 and ELISA) in SLE.
Methods We studied 83 patients (pts) with SLE (72 females, 9 males, median age 31,5, 16-65 years; the median diseases duration was 4 years, 2 months-36 years); 30 pts with others SARDs: 10 – Sjogren's syndrome; 10 – systemic sclerosis; 10 – rheumatoid arthritis; 38 pts with other RD: 10 – psoriatic arthritis, 8 – gout, 10 – osteoarthrosis, 10 – ankylosing spondylitis; 30 healthy controls (HC). ANA was determinated with IIF-HEp-2 by the AKLIDES automated system (“Medipan GmbH”, Germany) and ELISA on the “Alegria” analysator (“Orgentec”, Germany). Positive results of ANA measuring corresponded with the values ≥1:160 (IIF-HEp-2) and ≥1,3 U (ELISA).
Results The agreement of positive/negative results of ANA determination by IIF-HEp-2 and ELISA of RD pts and HC (n=181) was high (kappa=0,77). The results of ANA determination by the both methods matched in 88,4% of cases (positive – 47,5%, negative – 40,9% of pts). ANA determination by IIF-HEp-2 had more sensitivity in comparison with ELISA (93,9% and 81,9% respectively, p<0,02). By the level of positive likelihood ratio (+LR) (>2 and ≤5) both tests were applied to category of “useful” for SLE diagnosis. The negative likelihood ratio (-LR) of ANA determination by ELISA demonstrated “useful” diagnostic value of this test (>0,2 and ≤0,5). The –LR ANA determination by IIF-HEp-2 (0,08, p<0,001) was lower, than ELISA (0,25), and corresponded to the rank of tests, which are most “useful” for the exception of SLE diagnosis (<0,2) (Table 1).
Conclusions The results of the automated ANA determination by IIF-HEp-2 and ELISA have the high degree of correspondence and they allow to relate both tests to the amount of “useful” for SLE diagnosis. By the level sensitivity and –LR clinical value of ANA determination by IIF-HEp-2 had better results, then ELISA.
Disclosure of Interest None declared