Variables used in the marginal structural weight models
| Variable | Variable type |
|---|---|
| Demographics | |
| Age at symptom onset and at each assessment | Decades |
| Gender | Male/Female |
| Months from symptom onset at baseline and at each assessment | Tertiles by assessment |
| Smoking status at each assessment | Never smoked/Stopped ≥ 10 years before assessment/ Stopped <10 years before assessment/Current smoker |
| Serological and genetic | |
| Anti-CCP status at baseline (Axis-Shield DIASTAT kit) | <5 U/ml/≥5 U/ml |
| CRP category at baseline and assessment (end point immunoturbidimetric agglutination) | ≤ 10 mg/l/>10 mg/l |
| RF status at baseline and by assessment (latex agglutination) | <1:40/ ≥1:40 |
| Number of copies of the SE | 0/1/2 |
| Homozygous for SE | No/Yes |
| Disease activity and severity | |
| DAS28 score at baseline and assessment | |
| ACR criteria for RA cross-sectional at baseline and cumulative at assessment | Not met/Met |
| Number of swollen, tender and (both tender and swollen) joints at baseline and assessment | Tertiles by assessment |
| Presence of nodules at baseline and assessment | No/Yes |
| HAQ group at baseline and assessment | <1/≥1 to <2/≥2 |
| Presence of erosions by assessment | No/Yes |
| Larsen score by assessment | Tertiles by assessment |
| Physical Component Score (PCS) of SF36 | |
| Mental Component Score (MCS) of SF36 | |
| Diagnosed with any of 14 defined comorbidities by assessment | No/Yes |
| Treatment and hospital attendance | |
| Attended/referred to hospital since last assessment | No/Yes |
| Treated with SSZ, MTX, other DMARDs and steroids at baseline and by assessment | No/Yes |
| Ceased treatment since last assessment or by assessment due to inefficacy or adverse event | No/Yes |
| Remission by baseline and assessment | No/Yes |
ACR, American College of Rheumatology; anti-CCP, anti-cyclic citrullinated peptide; CRP, C-reactive protein; DAS28, 28 joint count Disease Activity Score; DMARDs, disease-modifying antirheumatic drugs; HAQ, Health Assessment Questionnaire; MCS, Mental Component Score; MTX, methotrexate; PCS, Physical Component Score; RA, rheumatoid arthritis; RF, rheumatoid factor; SE, shared epitope; SSZ, sulfasalazine.