Table 5

 Longitudinal regression analysis by generalised estimating equations on the levels of CTX-II, with longitudinal variables representing arthritis added with a time lag of three or six months

Standardised regression coefficient
No time lagTime lag 3 monthsTime lag 6 months
Figures represent standardised regression coefficients for the longitudinal relation between assessments of arthritis and CTX-II. The higher the value of the standardised regression coefficient, the stronger is the longitudinal relation between indices of arthritis and CTX-II. Asterisks indicate the level of significance for testing the hypothesis that the standardised regression coefficient  =  0 (no relation): *p<0.05, **p<0.01, ***p<0.001.
Model with three months time lag:
lnCTX-IIt  =  constant + a1.RF (0,1) + a2.treatment (0,1) + a3.RD (0,1) + b1.ESRt-3 months + b2.lnCTX-IIt-1 + c1.t + c2.t2
Model with six months time lag:
lnCTX-IIt  =  constant + a1.RF (0,1) + a2.treatment (0,1) + a3.RD (0,1) + b1.ESRt-6 months + b2.lnCTX-IIt-1 + c1.t + c2.t2
Small letters in italics are regression coefficients: a refers to baseline variables (fixed); b refers to longitudinal variables (time dependent), and c refers to time variables (RF, rheumatoid factor (0 = absent; 1 = present); treatment (0 = sulfasalazine; 1 = COBRA); RD, radiographic damage at baseline (0 = absent; 1 = present); lnCTX-II, the natural logarithm of CTX-II. See text for further explanations).
CTX-II, collagen type II; DAS28, 28 joint disease activity score; ESR, erythrocyte sedimentation rate.
Swollen joint count0.17***0.14**0.11*
Tender joint count0.080.020.00