Table 2.
Multiple Logistic Regression Models of Subclinical ILD and Multiple Linear Regression Models of Log-transformed Quantitative Fibrosis Score
| Age (yr) |
Male Sex |
Ever-Smoking |
MUC5B Genotype (GT/TT) |
RF Positive |
CCP Antibody Positive |
Current Methotrexate Use |
RA Disease Duration (yr) |
|||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Subclinical ILD | Odds Ratio | P Value | Odds Ratio | P Value | Odds Ratio | P Value | Odds Ratio | P Value | Odds Ratio | P Value | Odds Ratio | P Value | Odds Ratio | P Value | Odds Ratio | P Value |
| Primary model | 1.07 (1.03 to 1.11) | <0.001 | 1.22 (0.45 to 3.28) | 0.694 | 1.04 (0.46 to 2.39) | 0.918 | 2.49 (1.01 to 6.12) | 0.047 | — | — | — | — | — | — | — | — |
| Expanded model | 1.08 (1.04 to 1.13) | <0.001 | 1.40 (0.49 to 4.00) | 0.533 | 1.50 (0.59 to 3.83) | 0.400 | 2.71 (1.04 to 7.05) | 0.041 | 0.31 (0.10 to 0.98) | 0.046 | 1.94 (0.46 to 8.22) | 0.367 | 0.45 (0.18 to 1.16) | 0.098 | 0.99 (0.95 to 1.03) | 0.597 |
| Reduced model | 1.07 (1.03 to 1.11) | <0.001 | — | — | — | — | 2.56 (1.04 to 6.28) | 0.041 | — | — | — | — | — | — | — | — |
| Quantitative Fibrosis | Age (yr) |
Male Sex |
Ever-Smoking |
MUC5B Genotype (GT/TT) |
RF Positive |
CCP Antibody Positive |
Current Methotrexate Use |
RA Disease Duration (yr) |
||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Coefficient | P Value | Coefficient | P Value | Coefficient | P Value | Coefficient | P Value | Coefficient | P Value | Coefficient | P Value | Coefficient | P Value | Coefficient | P Value | |
| Primary model | 0.03 (0.02 to 0.04) | <0.001 | 0.37 (0.03 to 0.71) | 0.036 | 0.38 (0.12 to 0.65) | 0.006 | 0.49 (0.16 to 0.82) | 0.004 | — | — | — | — | — | — | — | — |
| Expanded model | 0.04 (0.03 to 0.05) | <0.001 | 0.38 (0.05 to 0.71) | 0.026 | 0.32 (0.06 to 0.57) | 0.016 | 0.60 (0.29 to 0.91) | <0.001 | −0.12 (−0.45 to 0.21) | 0.467 | 0.23 (−0.14 to 0.61) | 0.224 | 0.27 (0.01 to 0.53) | 0.043 | −0.00 (−0.02 to 0.01) | 0.553 |
| Reduced model | 0.03 (0.02 to 0.04) | <0.001 | 0.45 (0.11 to 0.79) | 0.011 | 0.33 (0.06 to 0.60) | 0.017 | 0.51 (0.19 to 0.84) | 0.002 | — | — | — | — | 0.26 (−0.01 to 0.52) | 0.058 | — | — |
Definition of abbreviations: CCP = cyclic citrullinated peptide; ILD = interstitial lung disease; RA = rheumatoid arthritis; RF = rheumatoid factor.
Primary model: Based on our hypothesis, we analyzed the association between the MUC5B promoter variant and subclinical ILD using logistic regression models adjusted for age, male sex, and smoking history (never, ever). Expanded model: Exploratory multivariable analysis adjusting for additional covariates of interest including RA disease duration, seropositivity to RF, seropositivity to CCP, and current methotrexate use. Reduced model: Sensitivity analysis performed by fitting a reduced model using backward stepwise selection (threshold P < 0.1; covariates considered included age, MUC5B, male sex, ever-smoking history, RA disease duration, seropositivity to RF, seropositivity to CCP, and current methotrexate use.