Interobserver variation of psoriasis area and severity index in a clinical setting

Background: Severity scoring systems are important parameters in assessing the severity of a disease aiding in categorization of disease and its prompt treatment. However, reliability of these scoring systems and inter-observer variation is a concern. In the recent years, there has been a lot of debate on reliability of Psoriasis Area and Severity Index (PASI) scoring as there is a wide range of difference in the scoring when assessed by each observer. We conducted this study to assess the inter-observer variation of PASI scoring observed in out-patient department of Dermatology at a tertiary care hospital. Methods: Total of 35 patients clinically presenting with chronic plaque type psoriasis, irrespective of disease duration and treatment taken were enrolled in the study. PASI scoring was assessed by 3 different observers (2st year, 3nd year postgraduate residents and clinical staff) independently on each patient and reliability was determined by intra-class coefficient. (ICC). Results: Our study showed an excellent reproducibility of PASI score when an inter-observer variation was performed. Most of the parameters showed an agreement of >0.9 (ICC) which was statistically significant (<0.001). However it was noted that “erythema” in head, upper limbs and lower limbs was in less agreement with ICC when compared to other parameters, yet excellent. Mean PASI score was 10.96, 10.78 and 10.47 among observer 1, 2 and 3 respectively. Conclusion: Our study concludes that PASI is a reproducible and reliable clinical tool with less inter-observer variation if done by trained qualified observers to assess the severity of chronic plaque type psoriasis although its application gets tedious and difficult in busy dermatology clinics. Limitation: A small sample size.