Two considerations for patients with psoriasis and their clinicians: What defines mild, moderate, and severe psoriasis? What constitutes a clinicallysignificant improvement when treating psoriasis?

The definitions of psoriasis severity and clinically significant improvemen t in psoriasis are used to classify treatments, obtain Food and Drug Admini stration approval, and determine product labeling and reimbursement. The Me dical Advisory Board of the National Psoriasis Foundation has addressed the se issues because of their importance in the clinical trials that are condu cted to gain FDA approval of indications. Narrow indications, which are wit hout a sound rational basis, will-in this era of constant oversight by thir d party payers-affect physicians' ability to manage patients with psoriasis . Body surface area (BSA) is usually used to define severity fur clinical t rials. It is not optimal for defining psoriasis severity because there are some patients with low BSA involvement who have very severe psoriasis and s ome patients with high BSA involvement who have mild psoriasis. We conclude that a quality of life (QOL) standard is better than BSA measurement for i dentifying patients with severe psoriasis. The second issue is what defines clinically significant improvement for patients with psoriasis. Setting an arbitrarily high criterion of clinical efficacy for new psoriasis treatmen ts will likely limit the development and approval of useful treatments. To maximize the availability of useful psoriasis treatments, it is our thesis that psoriasis treatments should be approved when they have been shown to p roduce a statistically significant level of improvement in well-designed cl inical trials.