PASI100

PASI100 is a clinical endpoint in dermatology describing complete skin clearance of psoriasis, defined as a 100 percent reduction from baseline in the Psoriasis Area and Severity Index (PASI). The PASI is a composite score that evaluates lesion severity—erythema, thickness, and scaling—and the extent of involvement across four body regions: head, upper limbs, trunk, and lower limbs. Each region is scored for severity (0-3 for each of three features) and area affected (0-6), with the total PASI ranging from 0 to 72. A PASI100 result corresponds to a final score of zero, indicating no detectable psoriatic plaques by standard assessment.

In clinical trials of systemic therapies, PASI100 is an indicator of complete or near-complete disease control and is reported alongside other endpoints such as PASI75 and PASI90. While many patients may achieve partial improvements, PASI100 remains a stringent target and is not reached by all patients even with effective treatments. The rate of PASI100 can vary by treatment class, patient population, and study design, and may be influenced by disease duration and affected body regions. The PASI100 endpoint gained prominence with the increased efficacy of biologic therapies during the 2010s.

Limitations include potential regional variation in clearance, differences in assessment timing, and the possibility that a zero PASI score does not fully capture patient experience or quality of life. Some patients may have residual symptoms in highly visible areas such as the scalp or nail psoriasis that are not always weighed the same in PASI calculations. Consequently, PASI100 is often interpreted in context alongside patient-reported outcomes and alternative assessments such as the static Physician's Global Assessment (sPGA).

See also: Psoriasis Area and Severity Index (PASI); PASI75; PASI90.

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