Factors associated with drug levels and anticertolizumab antibodies longitudinally over 12 months using GEE
| Variable | Certolizumab drug level β coefficient (95% CI) | p Value | ADAb level β coefficient (95% CI) | p Value |
|---|---|---|---|---|
| Univariate analysis | ||||
| Age | 0.14 (−0.017 to 0.29) | 0.08 | 0.021 (−2.16 to 2.21) | 0.99 |
| Female gender* | 4.76 (0.21 to 9.29) | 0.040 | −67.36 (−146.14 to 11.41) | 0.094 |
| BMI | −0.46 (−0.89 to −0.041)* | 0.032 | −0.92 (−6.03 to 4.19) | 0.72 |
| CRP | −0.099 (−0.17 to −0.029)* | 0.005 | 0.57 (−0.32 to 1.47) | 0.21 |
| ESR | −0.12 (−0.22 to −0.020)* | 0.019 | 0.40 (−0.95 to 1.74) | 0.58 |
| Baseline methotrexate use | −0.11 (−4.68 to 4.47) | 0.96 | −3.65 (−53.38 to 46.08) | 0.89 |
| Baseline methotrexate dose | 0.23 (0.33 to 0.78) | 0.43 | 4.94 (3.74 to −13.6) | 0.27 |
| Baseline oral steroid use | 3.15 (−1.89 to 8.20) | 0.22 | −29.77 (−69.54 to 10.0) | 0.14 |
| Any nbDMARD use at baseline† | 3.15 (−1.89 to 8.20) | 0.22 | −54.66 (−125.37 to 16.05) | 0.14 |
| Antidrug antibody level | −0.037 (−0.055 to −0.018)* | <0.0001 | – | |
| Certolizumab drug level | – | – | −2.56 (−4.09 to −1.03)* | 0.001 |
| Adherence | 10.43 (4.76 to 16.11)* | <0.0001 | −45.05 (−108.35 to 18.25) | 0.16 |
| Multivariate model‡ | ||||
| Antidrug antibody level | −0.044 (−0.059 to −0.028)* | <0.0001 | – | |
| Adherence | 7.08 (0.71 to 13.45)* | 0.029 | – | |
| Female gender | 1.77 (−4.21 to 7.76) | 0.56 | – | |
| BMI | −0.13 (−0.68 to 0.43) | 0.65 | – | |
| CRP | −0.065 (−0.14 to 0.013) | 0.102 | – | |
*p<0.05.
†nbDMARD use included methotrexate, sulfasalazine, leflunomide or hydroxychloroquine at baseline.
‡Adjusted for variables significant in the univariate analysis. CRP was used instead of ESR in the multivariate model, as was measured in all patients. In the second column, certolizumab drug level is used as the dependant variable in the GEE model; in the fourth column, anticertolizumab antibodies are used as the dependant variable in the GEE model.
ADAb, antidrug antibody; BMI, body mass index; ESR, erythrocyte sedimentation rate; GEE, generalised estimating equation; nbDMARD, non-biologic disease-modifying antirheumatic drug.