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 lag | Time lag 3 months | Time 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 count | 0.17*** | 0.14** | 0.11* |
| Tender joint count | 0.08 | 0.02 | 0.00 |
| ESR | 0.24*** | 0.13* | 0.10 |
| DAS28 | 0.22*** | 0.13* | 0.08 |