Table 4. Multiple linear regression analyses for determinants of ASAS HI sum scores in patients with ankylosing spondylitis.
| Univariable | Multivariable* | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Model A | Model B | Model C | Model D | ||||||||
| Variable | B (95% CI) | P | VIF | B (95% CI) | P | B (95% CI) | P | B (95% CI) | P | B (95% CI) | P |
| Gender, male | −1.60 (−2.58–−0.62) | 0.002 | 1 | −1.48 (−2.47–−0.49) | 0.004 | −2.30 (−3.28–−1.13) | <0.001 | −1.91 (−2.82–−1.00) | <0.001 | −1.91 (−2.80–−1.02) | <0.001 |
| Age, year | 0.04 (0.01–0.07) | 0.005 | 2 | −0.02 (−0.06–0.02) | 0.311 | 0.00 (−0.04–0.04) | 0.894 | -0.01 (−0.05–0.02) | 0.545 | -0.01 (−0.05–0.03) | 0.546 |
| Disease duration, year | 0.05 (0.02–0.09) | 0.001 | 2 | 0.05 (0.01–0.09) | 0.014 | 0.04 (−0.001–0.08) | 0.057 | 0.03 (-0.002–0.07) | 0.066 | 0.03 (-0.002–0.07) | 0.066 |
| Smoking, n (%) | 0.25 (−0.55–1.07) | 0.541 | 0.39 (-0.39–1.17) | 0.322 | 0.30 (-0.49–1.08) | 0.454 | 0.40 (-0.32–1.11) | 0.273 | 0.40 (-0.32–1.11) | 0.274 | |
| No. of comorbidities | 0.43 (0.10–0.76) | 0.010 | 1 | 0.16 (-0.18–0.51) | 0.357 | 0.16 (-0.18–0.51) | 0.354 | 0.16 (-0.16–0.48) | 0.325 | 0.16 (-0.16–0.48) | 0.325 |
| Extra-spinal manifestation | 1.07 (0.27–1.86) | 0.009 | 1 | 0.16 (−0.56–0.87) | 0.664 | 0.19 (−0.53–0.91) | 0.610 | 0.14 (−0.52–0.80) | 0.673 | 0.14 (−0.51–0.80) | 0.673 |
| Family history of AS | 0.26 (-0.55–1.08) | 0.529 | 0.01 (-0.70–0.73) | 0.975 | 0.04 (-0.68–0.76) | 0.922 | -0.06 (-0.72–0.60) | 0.864 | -0.06 (-0.72–0.60) | 0.864 | |
| ESR, mm/hour | 0.04 (0.01–0.07) | 0.003 | 5 | 0.00 (−0.02–0.02) | 0.993 | ||||||
| CRP, mg/dl | 0.25 (−0.01–0.50) | 0.057 | 0.00 (−0.21–0.21) | 0.999 | |||||||
| ASDAS-ESR | 2.14 (1.71–2.57) | <0.001 | 18 | 1.93 (1.48–2.37) | <0.001 | ||||||
| ASDAS-CRP | 1.77 (1.36–2.18) | <0.001 | 5 | 1.68 (1.28–2.08) | <0.001 | ||||||
| BASDAI | 1.38 (1.17–1.60) | <0.001 | 7 | 1.30 (1.08–1.52) | <0.001 | 1.30 (1.08–1.52) | <0.001 | ||||
| mSASSS | 0.02 (0.01–0.04) | 0.007 | 1 | 0.02 (-0.002–0.03) | 0.081 | 0.02 (-0.002–0.03) | 0.090 | 0.02 (0.01–0.04) | 0.007 | 0.02 (0.01–0.04) | 0.007 |
| AIC | 1003 | 1007 | 951# | 951# | |||||||
*Gender, age, disease duration, smoking, number of comorbidities, extra-spinal manifestations, family history of AS, mSASSS, and disease activity (model A, ASDAS-ESR; model B, ASDAS-CRP; model C, BASDAI+ESR; model C, BASDAI+CRP) were included in the multivariable analyses.
Abbreviations: ASAS HI, assessment of spondyloarthritis international society health index; P, p-value; CI, confidence interval; n, number; ESR, erythrocyte sedimentation rate; CRP, C-reactive protein; ASDAS, ankylosing spondylitis disease activity score; BASDAI, Bath ankylosing spondylitis disease activity index; mSASSS, modified Stoke ankylosing spondylitis spinal score, AIC, Akaike information criterion.
#The AIC in model C (951.35226) is trivially lower than that in model D (951.35234).