Computer-aided measurement of psoriatic lesion area in a multicenter clinical trial--comparison to physician's estimations.

Background: There is a great need for accurate and informative outcome measures in clinical trials. In psoriasis, therapeutic effect is usually assessed by physician's estimation of psoriatic area and other signs. These measures were found to be un-reproducible. Several automated procedure for more reproducible measurement of psoriatic area were developed, but were not suitable for large-scale trials.

Objectives: In a multicenter clinical trial, we tested a method where the advantage of accurate computerized measurement of the area on the digital photograph was combined with physician's proficiency.

Methods: The patients with psoriasis in four study centers were included in a placebo controlled clinical trial. They were examined and photographed before and after the therapy with calcipotriol ointment or placebo. The psoriatic area was manually outlined on the patient's photographs and the area was automatically measured by a computer. The areas estimated by physician and measured by computer were compared.

Results: We found that computer-aided measurement of psoriatic lesion area improved the power of the clinical trial, compared to the standard approach, where physician's estimations of the psoriatic lesion area tend to overestimate. We also found that adapted PASI index, where the psoriatic area was not converted into an area grade, but was maintained as a continuous variable, also improved the power of the clinical trial.

Conclusions: Computer-aided measurement and an adapted PASI can be used as a powerful and reliable measure to evaluate the effects of antipsoriatic treatment.