Abstract

The purpose of the present study was to investigate the value of different markers of collagen metabolism in assessing the disease process and further disease progression in patients with inflammatory arthritis, mainly rheumatoid arthritis (RA).

In a series of 59 patients with RA and knee joint effusion, the level of synovial fluid (SF) carboxyterminal telopeptide of type I collagen (ICTP), a marker for type I collagen degradation, was associated with the Larsen’s grade of the corresponding joint (p < 0.001). The mean SF concentrations of ICTP and the markers of type I and III collagen synthesis (the aminoterminal propeptides of type I and III procollagens, PINP and PIIINP) were higher than those in serum. In addition, the levels of these markers correlated with each other in both serum and SF (p < 0.001 in both occasions).

In a three-year follow-up study of 44 RA patients from the abovementioned series and 11 patients with other chronic arthritides, a high SF ICTP level turned out to reflect accelerated radiological progression in the assessed joint (p < 0.05). Contrary to this, the results on the SF leukocyte level were contradictory.

In a population-based cross-sectional series of 90 patients with advanced RA, elevated baseline serum ICTP levels discriminated the patients with a need for total joint replacement surgery from those with milder disease (p = 0.001) in a three-year follow-up. In a study of 52 patients with recent onset RA, the changes in BMD during a two-year follow-up were not associated with the serum level of markers of type I collagen metabolism. In this series, however, the decrease in BMD (measured in the spine and the femoral neck) was smaller than earlier reported.

In a three-year follow-up series of 63 patients with early RA, the patients with simultaneously elevated serum ICTP (> 4.6 mg/l) and RF positivity at baseline, had an increased risk for progressive joint disease (an increase in Larsen’s score > 20 as assessed from radiographs of hands and feet) with an odds ratio of 9.1 (95% CI 2.5 to 32.9). A risk profile of this kind may be useful in early disease assessment to identify the patients who will need the most active drug therapy.