Table 1.
Variables used in the marginal structural weight models*
| Variable | Variable type |
|---|---|
| Demographics | |
| Age at symptom onset and at each assessment | Decades |
| Sex | 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 prior to assessment | |
| Stopped <10 years prior to assessment | |
| Current smoker | |
| Serologic and genetic | |
| Anti-CCP antibody status at baseline (Axis-Shield DIASTAT kit) | <5 units/ml |
| ≥5 units/ml | |
| CRP level category at baseline and assessment (end-point immunoturbidimetric agglutination) | ≤10 mg/liter |
| >10 mg/liter | |
| RF status at baseline and assessment (latex agglutination) | <1:40 |
| ≥1:40 | |
| Number of copies of the shared epitope | 0 |
| 1 | |
| 2 | |
| Homozygous for the shared epitope | 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 swollen and tender joints at baseline and assessment | Tertiles by assessment |
| Presence of nodules at baseline and assessment | No |
| Yes | |
| HAQ score 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 of the SF-36 | |
| Mental component score of the SF-36 | |
| 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 |
*
Anti-CCP = anti–cyclic citrullinated peptide; CRP = C-reactive protein; RF = rheumatoid factor; DAS28 = Disease Activity Score in 28 joints; ACR = American College of Rheumatology; RA = rheumatoid arthritis; HAQ = Health Assessment Questionnaire; SF-36 = Medical Outcomes Study Short Form 36; SSZ = sulfasalazine; MTX = methotrexate; DMARDs = disease-modifying antirheumatic drugs.