A statistical model to predict the reduction of lichenification in atopic dermatitis

Acute symptoms of atopic dermatitis (AD), such as erythema, oedema/papulations and excoriations, respond quickly to topical corticosteroid treatment. Conversely, lichenification is regarded as a troublesome non-acute symptom of chronic AD which can take months of treatment before any improvement is seen. However, very little data actually support this opinion. Here, we analyse lichenification scores in 3 multicentre, short-term studies of nearly similar design. Two of these studies were active comparator dosage trials administered with either fluticasone propionate cream or ointment once or twice daily, the third study was a placebo control. In each of these 4-weeks studies lichenification was measured weekly. For the evaluation of the lichenification score over time a random-coefficients regression model was used. In all active treatments lichenification significantly improved (p < 0.005) within one week. Improvement continued afterwards, with > 80% of patients scoring no, very mild or mild lichenification after 4 weeks. We developed a model in which the lichenification score drops off linearly with the square root of time. The resulting convexly shaped downward time trend of lichenification was significant during all treatments and was significantly stronger during active treatment than with placebo. Fluticasone propionate can improve moderate to severe lichenification in a relative short period of time.