MEASUREMENT OF ANTI-DSDNA - A COMPARATIVE-STUDY OF 2 ELISA AND THE CRITHIDIA ASSAY

We compared the measurement of anti-dsDNA by a commercial ELISA test ( DIASTAT), an in-house ELISA and the Crithidia luciliae assay in cross- sectional sera samples of 209 systemic lupus erythematosus (SLE) patie nts and 64 patients with a variety of rheumatological, autoimmune and non-autoimmune diseases in Hong Kong, The Crithidia assay was found to be the least sensitive (17%) but most specific (95%) method for detec tion of a positive result in SLE patients, The DIASTAT assay has a hig her sensitivity (68%) but lower specificity (80%) than the in-house EL ISA test (32% sensitivity and 89% specificity). The positive predictiv e value of the three assays are comparable at 90-92% while DIASTAT had the highest negative predictive value (44%), There was good linear co rrelation (r = 0.7) between the two ELISAs. ELISA can serve as a usefu l screening test for anti-dsDNA in SLE patients and doubtful cases can then be confirmed by another method such as radio-immunoassay.