Serum lipoprotein(a) and apolipoprotein(a) phenotypes in patients with rheumatoid arthritis

Objective. To determine serum lipoprotein(a) (Lp[al) concentrations and to analyze the apolipoprotein(a) (Apo[a]) phenotype in patients with rheumatoid arthritis (RA). Methods. The subjects included 131 patients with RA and 200 healthy control subjects. Serum Lp(a) concentrations were measured by enzyme-linked immunosorbent assay, and the Apo(a) phenotype was determined by immunoblotting. HLA-DR typing was also done. Results. The mean serum Lp(a) level was significant ly higher (P < 0.001) in the RA patients (27.5 mg/dl) than in the controls (15.0 mg/dl), The S3 allele was found in 70.0% of the patients versus 39.5% of the controls (P < 0.001). There was no significant difference in HLA-DR4 positivity between patients with and without the S3 phenotype. Conclusion. The serum Lp(a) level was increased in patients with RA, possibly partly because of S3 phenotype predominance.