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

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).

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.

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.

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.