The PASI (psoriasis area and severity index) can be used to evaluate the severity of psoriasis at a given time. Plotting a patient’s PASI over time gives a curve reflecting the severity of the psoriasis over the period. E-PAP (evaluation for prognosis with averaged PASI) is the average area under the curve for this plot. This can be helpful in monitoring the long-term follow-up of patients under treatment.


AP(n) = area under curve for interval plot of days versus PASI score =

= (((PASI on evaluation day n) + (PASI on evaluation day n+1)) / 2) * (number of days between evaluation day n and evaluation day n+1)



= SUM(AP(n) for period) / (total number of days in period)


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