Development and pilot-testing of a psoriasis screening tool

Background There is a need to validate psoriasis self-reports in epidemiological studies, where individuals may not be seeing dermatologists or other health care providers. Objectives To develop and pilot test the Psoriasis Screening Tool (PST) in an ambulatory setting. Patients and methods The PST was designed with eight closed-ended questions requiring a 'yes' or 'no' response. Typical images of skin, nail and scalp changes in psoriasis were included with respective questions. We administered the PST to 222 consecutive individuals being seen at a dermatology clinic. All English-speaking subjects completed the PST without assistance. A board-certified dermatologist established the diagnosis of psoriasis or excluded psoriasis in all participants. Results A total of 222 completed PST questionnaires were included for analysis. There were 111 individuals in the psoriasis group and 111 individuals in the nonpsoriasis group. A combination of three questions resulted in a sensitivity of 96·4% [95% confidence interval (CI) 93·2-98·0] and specificity of 97·3% (95% CI 94·1-98·9) for psoriasis. Adding a pictorial question increased the sensitivity of the screening tool to 98·2% (95% CI 95·0-99·5). Of the 111 individuals with psoriasis, 69% answered yes to having plaque-type psoriasis, 50% answered yes to having nail involvement, 66% answered yes to having scalp involvement, and 59% answered yes to having inverse-type psoriasis. Conclusions This pilot study suggests that the PST can distinguish individuals with psoriasis from individuals without psoriasis in an English-speaking population being seen at an outpatient dermatology clinic. Furthermore, the PST may be used to identify psoriasis phenotypes. Although the PST may be limited by spectrum bias in this pilot study, we believe it remains a reliable tool to collect information on psoriasis in remote populations.