Comparison of different methods for the detection ofanti-Ro/SSA antibodies in connective tissue diseases.

OBJECTIVE: To compare the performance characteristics of various tests commonly used to detect anti-SSA/Ro autoantibodies in the sera of patients affected by connective tissue diseases (CTD). METHODS: Indirect immunofluorescence (IIF) with HEp-2000 as substrate (ImmunoConcepts, USA), Ouchterlony's double immunodiffusion (ID) (home made), commercial Varelisa ReCombi anti-Ro kit (Pharmacia & Upjohn, Germany), research kits (60 kDa and 52 kDa) with human recombinant antigens (Pharmacia & Upjohn, Germany) and a commercial western blot (WB) kit (MarDx, USA) were evaluated in our study. Sixty-four sera from patients affected by CTD were tested: 15 had primary Sjögren's syndrome (SS), 34 only had sicca syndrome, and 15 had systemic lupus erythematosus (SLE). Thirty sera from healthy subjects were selected as controls. RESULTS: 54 sera were positive by at least one method. The specificity of all tests was good. The prevalence of anti-SSA antibodies on 54 positive sera was 76% (ID), 89% (IIF), 89% (Varelisa), 89% (ELISA Ro-60 kDa), 67% (ELISA Ro-52 kDa) and 85% (WB). Some differences were found between WB and ELISA in the detection of anti-60 kDa SSA and anti-52 kDa SSA; in 3 SS sera only anti-52 kDa protein was found by WB. CONCLUSION: Our data confirm that, although IIF HEp 2000 (Immuno Concepts) and Varelisa anti-Ro (Pharmacia & Upjohn) both performed well, a combination of 2 or more methods must still be recommended for anti-SSA antibody detection