Patients' visual analogue scale: a useful method for assessing psoriasis severity.

The quality of life of patients with psoriasis can be severely diminished. The disease often affects life at a physical, social and emotional level (1). In clinical studies, a wide variety of assessment tools is used to evaluate the severity of psoriasis, but there is a lack of standardization (2). The introduction of quality of life (QoL) instruments has improved psoriasis evaluation, but there is a need for consensus in order to make valid comparisons between studies (3). The Psoriasis Area and Severity Index (PASI) is the most commonly used method to describe severity of psoriasis, and the Dermatology Life Quality Index (DLQI) is the most common method for measuring QoL in randomized controlled trials (4). The visual analogue scale (VAS) is an often-used tool to measure subjective phenomena, which has shown good reliability and validity in terms of assessment of pain (5). The aim of this study was to compare the simple VAS instrument with the most-used instruments for measuring psoriasis severity and QoL.