Comparison of potential limitations when evaluating cutaneous psoriasis in trials with patients with psoriasis vs PsA.
| Variable or Factor | Psoriasis Trials | PsA Trials | Potential Risk of Bias |
|---|---|---|---|
| Primary endpoint | Psoriasis severity endpoint (eg, % reaching PASI75 or clear/almost clear compared to PBO) | Rheumatologic endpoint (eg, % reaching ACR20 compared to PBO) | Differences in statistical methodologies of evaluating primary and secondary endpoints |
| Baseline psoriasis severity | Moderate-severe (PASI12, BSA 10%, and sPGA ≥ 3 or moderate) | Presence or history of plaque psoriasis | Median baseline PASI scores in mild-moderate range, affecting validity (sensitivity to change) of metrics like PASI |
| Inclusion of patients in analysis | All randomized patients included in analysis | Some randomized patients excluded in analysis if baseline involvement is < 3% BSA | Potential inconsistency |
| Concomitant therapies | Washouts required for all DMARDs/systemic immunomodulatory agents (eg, MTX or prednisone) | Concomitant MTX, prednisone, or other csDMARD frequently allowed if on stable doses | Imprecision: small percentage of patients may reach PASI75, affecting effect size and confidence in effect |
| Typical efficacy assessor | Trained dermatologist | Trained rheumatologist | Imprecision: potential risk of interrater or intrarater reliability |
| Phenotype differences | Plaque psoriasis, typically without moderate-to-severe PsA | Plaque psoriasis with moderate-severe PsA | Plaque psoriasis may be biologically different in patients with PsA |
| Psoriasis morphology differences | Plaque, primarily on trunk and extremities | Plaque, but may have increased prevalence of nail, scalp, palmoplantar, intertriginous involvement | Imprecision and inconsistency: morphology of plaque psoriasis on the trunk and extremities differs from intertriginous or palmoplantar, affecting PASI metrics of induration, scale, and erythema, or responsiveness to therapy |
ACR20: American College of Rheumatology criteria of > 20% improvement since baseline; BSA: body surface area; csDMARD: conventional synthetic disease-modifying antirheumatic drugs; DMARD: disease-modifying antirheumatic drugs; MTX: methotrexate; PASI: Psoriasis Area and Severity Index; PASI75: ≥ 75% improvement of PASI since baseline; PBO: placebo; PsA: psoriatic arthritis; sPGA: static physician global assessment.