Performance evaluation of a line blot assay system for detection of anti-PM-Scl antibody in Japanese patients with systemic sclerosis.

OBJECTIVE

To evaluate the performance of a line blot (LB) assay for identifying anti-PM-Scl antibody (Ab).

METHODS

We screened 56 serum samples from systemic sclerosis patients using a protein immunoprecipitation (IP) assay and an LB assay (Systemic Sclerosis Profile Euroline® Blot test kit) to detect anti-PM-Scl Ab. We compared the results obtained by the IP and LB assays.

RESULTS

Among the 56 serum samples of SSc patients, 9 sera were positive for anti-PM-Scl75 Ab and 1 for anti-PM-Scl100 Ab by the LB assay. The protein IP assay revealed that none of the samples precipitated 75 or 100 kDa proteins identical to the anti-PM-Scl Ab reference serum, regardless of the positive or negative results obtained in the LB assay. Therefore, the false-positive rates for both anti-PM-Scl75 Ab and anti-PM-Scl100 Ab by the LB assay were 100%.

CONCLUSION

Detection of anti-PM-Scl Ab assessed with a commercial LB assay requires extreme caution since it may yield false-positive data.