To test the predictive value of the cross-linked carboxyterminal telopeptide of type I collagen (ICTP; a marker of type I collagen degradation), rheumatoid factor (RF) and C-reactive protein (CRP) for disease progression in patients with early rheumatoid arthritis (RA) METHOD: We tested the value of baseline values of RF, CRP and ICTP for the prediction of radiological joint progression over 3 yr in 63 consecutive patients with early RA who were treated with the 'saw-tooth strategy'.
Age- and sex-adjusted risks as odds ratios (95% confidence intervals) of elevated serum ICTP, RF positivity and increased CRP for progressive joint disease (defined as an increase of > 20 in Larsen's index on radiographs of the hands and feet) were 3.9 (1.3, 11.9), 3.9 (1.0, 15.5) and 2.6 (0.9, 7.5), respectively. Better prediction was achieved when the tests were used in combination, and where there was both elevated ICTP and positive RF the odds ratio was 9.1 (2.5, 32.9). This test combination showed good sensitivity and specificity (71 and 77%, respectively), with a positive predictive value of 65% and a likelihood ratio of 3.1.
This kind of risk profile, in which the tests used reflect different aspects of the disease process, may be useful in early disease assessment to find patients who will need the most active drug therapy.