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

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Abstract
Objective To determine serum lipoprotein(a) (Lp[a]) 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 significantly 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.