Multivariable logistic regression analysis of treatments and other factors associated with medication adherence*
| Parameter (retained based on backward selection) | Component being rated | OR (95% CI)† | ||
| RA population | PsA population | AS population | ||
| Treatment | ||||
| csDMARD-TNFi combination | TNFi | 5.45 (3.35 to 8.87)‡ | 1.22 (0.54 to 2.75) | 22.69 (6.34 to 81.21)‡ |
| NSAID-TNFi combination | TNFi | NA | NA | 6.33 (1.84 to 21.84)‡ |
| TNFi monotherapy | TNFi | 3.63 (1.72 to 7.69)‡ | 1.23 (0.55 to 2.73) | 13.10 (4.27 to 40.18)‡ |
| csDMARD monotherapy | csDMARD | Reference | Reference | 1.27 (0.20 to 7.86) |
| csDMARD-TNFi combination | csDMARD | 2.09 (1.35 to 3.25)‡ | 0.50 (0.22 to 1.10) | 3.23 (0.99 to 10.58) |
| NSAID-csDMARD combination | csDMARD | NA | NA | 1.19 (0.28 to 5.08) |
| csDMARD-TNFi combination | NSAID | NA | NA | 1.69 (0.38 to 7.57) |
| NSAID-TNFi combination | NSAID | NA | NA | 1.15 (0.33 to 4.04) |
| NSAID-csDMARD combination | NSAID | NA | NA | 1.19 (0.28 to 5.08) |
| Sociodemographic factors | ||||
| Age, years | 1.05 (1.03 to 1.06)‡ | 1.07 (1.04 to 1.11)‡ | 1.03 (1.01 to 1.06)‡ | |
| Race (white vs other) | 2.25 (1.51 to 3.36)‡ | ― | 3.10 (1.66 to 5.78)‡ | |
| Sex (female vs male) | ― | ― | 1.73 (0.96 to 3.12) | |
| Illness perception | ||||
| BIPQ item 1—Consequences | ― | ― | 1.10 (0.99 to 1.23) | |
| BIPQ item 2—Timeline | 1.08 (1.00 to 1.17) | ― | ― | |
| BIPQ item 8–Emotional Representation | ― | ― | 0.86 (0.77 to 0.95)‡ | |
| Disease-/medication-related factors | ||||
| Disease duration, years | 0.97 (0.95 to 0.99)‡ | ― | ― | |
| Number of pretreatments (>3 vs ≤3) | ― | ― | 0.34 (0.16 to 0.72)‡ | |
| Duration of current treatment, years | ― | 0.91 (0.85 to 0.97)‡ | ― | |
| Treatment response (complete vs non-complete)§ | ― | 2.19 (1.17 to 4.09)‡ | ― | |
| Beliefs factors | ||||
| BMQ-Specific Necessity | 1.12 (1.07 to 1.18)‡ | 1.13 (1.04 to 1.23)‡ | 1.18 (1.09 to 1.28)‡ | |
| BMQ-Specific Concerns | 0.92 (0.87 to 0.97)‡ | ― | ― | |
| BMQ-General Harm | 0.88 (0.83 to 0.95)‡ | 0.85 (0.77 to 0.94)‡ | ― | |
― = eliminated from model; NA=not applicable (NSAIDs were only taken by patients with AS; therefore there are no data for NSAID-containing regimens for patients with RA and PsA).
*Adherence was defined as a binary variable: highly adherent (MMAS-4© score=4) or not highly adherent (MMAS-4© score <4).
†Except where noted, ORs represent the impact of treatment vs reference (csDMARD in csDMARD monotherapy for RA and PsA; NSAID monotherapy for AS) or the impact of a 1-unit or 1 year increase (other factors); empty cells denote that a variable was not selected in the regression model for the respective indication.
‡P<0.05 vs OR of 1.
§Determined by treating physician; treatment response was categorised as ‘complete response’, ‘partial response’, ‘no response’ or ‘not evaluable’.
AS, ankylosing spondylitis; BIPQ, Brief Illness Perception Questionnaire; BMQ, Beliefs about Medicines Questionnaire; GC, glucocorticoid; IMID, immune-mediated inflammatory disease; MMAS-4©, 4-item Morisky Medication Adherence Scale; NA, not applicable; NSAID, non-steroidal anti-inflammatory drug; OR, odds ratio; PsA, psoriatic arthritis; RA, rheumatoid arthritis; TNFi, tumour necrosis factor inhibitor; csDMARD, conventional synthetic disease-modifying antirheumatic drug.