HLA-DRB1 genes, rheumatoid factor, and elevated C-reactive protein: independent risk factors of radiographic...

To evaluate the prognostic value of HLA-DRB1 antigens, rheumatoid factor (RF), and C-reactive protein (CRP) with the radiographic outcome of rheumatoid arthritis (RA).

In total, 139 patients with early RA (< 2 years) were followed up. At the end of 3 year treatment with disease modifying antirheumatic drugs (DMARD) HLA genotyping and external radiographic scoring were performed. The time up to the first development of erosive disease [Ratingen radiographic score (RS) > 0, > 5, > 10] was compared by methods of survival analysis.

At 4 years' disease duration, DRB1*04 or DRB1*01 positive patients had RS > 0 or > 10 (73% and 27%, respectively) significantly more frequently than DRB1*04 or DRB1*01 negative patients (37% and 7%, respectively). Nearly independently of the genetic predisposition, RF and elevated CRP at the start of DMARD treatment were predictive for erosive RA at 4 years. Elevated CRP (> or = 15 mg/l) increased the probability of erosive RA in DRB1*04 or DRB1*01 positive patients from 64.0% (in patients with CRP < 15 mg/l) to 83.9%, and in DRB1*04 and DRB1*01 negative patients from 18.8% to 70.1%. The corresponding figures for RF+ and RF- patients were 58.2% and 82.5% in HLA predisposed patients and 23.5% and 60.2% in those who were negative for DRB1*04 and DRB1*01. The probability of a RS > 10 was 40.9% for HLA predisposed patients with elevated CRP. In contrast, no case with RS > 10 was found in 43 patients who had neither of these 2 risk factors.

Our findings support that HLA predisposition plays an important role with regard to radiographic progression. However, this effect is modified by RF serum concentration and disease activity.