BSA75, BSA90, and BSA100: New Clinical Tools for Measuring Improvement in Psoriasis

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Currently, there is no widely accepted tool for assessing the severity of psoriasis in the clinical setting.1-5 Moreover, there is still a need for a simple assessment tool to assist in evaluating a patient’s response to therapy in clinical practice.6

The body surface area (BSA) is a familiar and widely used measurement by clinicians. It is easily calculated by the rule of nines or with the patient’s open palm and thumb approximating 1% of the BSA.7 Body surface area is an uncomplicated concept for patients to understand and interpret. It also promotes patient empowerment and self-care by allowing patients to monitor short-term and long-term response to therapy.

The National Psoriasis Foundation Medical Board published treatment targets for plaque psoriasis. One of the conclusions states, “The acceptable response at 3 months postinitiation was either BSA 3% or less or BSA improvement 75% or more from baseline.”8

We propose a new nomenclature that a 75% improvement in BSA be recognized as BSA75, a 90% improvement in BSA as BSA90, and a 100% improvement in BSA as BSA100. These classifications would be analogous to corresponding improvements in the following psoriasis area and severity index (PASI) scores: PASI 75, PASI 90, PASI 100.9 A loss of BSA goals/milestones (ie, BSA75) could encourage and facilitate physician-patient conversations and further direct modifications to disease management and treatment therapy.

A potential drawback to the implementation of this novel categorization system is that other notable aspects of psoriasis would not be assessed, such as erythema, induration, or scale; subjective measurements; patient quality of life; patient symptoms; areas of involvement (eg, palms, soles of feet); and disease course. Nevertheless, the BSA75, BSA90, and BSA100 classifications can serve as practical, objective, and straightforward tools to monitor disease progression and treatment response in psoriasis patients, which may potentially promote improved patient outcomes in clinical practice.

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