Anti-SSA/Ro antibody determination by enzyme-linked immunosorbent assay asa supplement to standard immunofluorescence in antinuclear antibody screening

The aim of this study was to investigate the frequency and possible clinica l relevance of SSA/Ro antibodies, as determined by enzyme-linked immunosorb ent assay (ELISA), in patient sera not exhibiting a concomitant positive re action by the standard immunofluorescence (IF) test using HEP-2 cells as su bstrate. SSA/Ro reactivity, as shown by ELISA, was found in 285 (7%) of 402 5 serum samples consecutively remitted for antinuclear antibody (ANA) scree ning. Seventy-five of these serum samples (26%), derived from 64 patients, were negative by the IF-ANA screening test. Serum samples from all 64 patie nts exhibiting SSA/Ro reactivity by ELISA without concomitant positivity by IF-ANA were further investigated by IF using transfected HEP-2 cells hyper expressing the 60,000 MW SSA/Ro antigen (HEP-2000(R)) and by immunodiffusio n (ID) and Western blot. In 55 of these 64 patients, SSA/Ro reactivity coul d be verified by one or more of the other techniques investigated. Twelve o f these patients fulfilled four or more American College of Rheumatology (A CR) criteria for systemic lupus erythematosus (SLE) and another five patien ts exhibited a histologically confirmed cutaneous lupus erythematosus (LE). In four of the 12 IF-ANA-negative patients with a diagnosis of SLE, the SS A/Ro reactivity was only detectable by ELISA and Western blot. In conclusio n, the use of a sensitive ELISA assay could provide a clinically important supplement to the routine ANA screening by IF, which does not detect certai n anti-SSA/Ro-containing sera among patients with relevant autoimmune diagn oses. Detection of anti-SSA/Ro antibodies, however, does not alone signify cutaneous LE or SLE but adds weight to these diagnoses that should rely hea vily on other clinical information.