Abstract
Patients with psoriasis attending general practitioner and dermatology clinics may complain about their joints, but it may be difficult for the nonrheumatologist to distinguish psoriatic arthritis (PsA) from other forms of arthritis. A screening tool for PsA would therefore be useful to both general practitioners and dermatologists and help identify patients for further evaluation by a rheumatologist. Although several screening tools have been developed, the Psoriasis Epidemiology Screening Tool (PEST) has the advantage of simplicity and ease of use. This new instrument consists of 5 simple questions supported by the addition of a manikin for patient markup. During development, the questionnaire has shown a sensitivity of 0.94 and a specificity of 0.78. Further validation of this and the other questionnaires is now required. A “head to head” study of the PEST, ToPAS (Toronto Psoriatic Arthritis Screening questionnaire), and PASE (Psoriatic Arthritis Screening and Evaluation) tools is planned in a secondary-care population with psoriasis. This study is important not only to confirm the comparative performance of the instruments, but also to confirm the high figures for sensitivity in a secondary-care population.
In a presentation at the 2009 annual meeting of GRAPPA (Group for Research and Assessment of Psoriasis and Psoriatic Arthritis) in Stockholm, Sweden, the author described the development of the Psoriasis Epidemiology Screening Tool (PEST), which was developed to screen for psoriatic arthritis (PsA) in patients with psoriasis1.
The questions used in the development of PEST were derived from the Psoriatic Arthritis Questionnaire (PAQ), an instrument originally developed in Canada in the late 1990s and modified by Alenius, et al2. To the core questions in that questionnaire were added other questions used in epidemiological surveys in France3 and a final question about dactylitis, making 16 questions in all. These questions, together with a figure of a manikin for patient markup1, were sent by post to a sample of patients with psoriasis identified from the electronic databases of 2 large general practices in Bradford, West Yorkshire, UK. Subsequently, a random sample of respondents was invited for a full examination in the rheumatology clinic of St. Lukes Hospital, Bradford, where the presence of PsA was established, using the CASPAR (Classification of Psoriatic Arthritis) criteria. This process enabled a more complete statistical analysis of the value of individual questions in detecting the presence of PsA, and the significant predictors were entered into a multivariate model to enable data reduction and the elimination of redundancy. The resulting more concise 5-question PEST instrument is shown in Figure 1. The comparative performance of the PEST and the PAQ (Swedish modification) was examined by receiver-operating characteristic (ROC) analysis and is reproduced in Table 1.
The PEST screening questionnaire for psoriatic arthritis (in people with psoriasis). Score 1 point for each question answered in the affirmative. A total score of 3 or more indicates psoriatic arthritis (sensetivity 0.97, specificity 0.79, positive predictive value 0.65, negative predictive value 0.99). From Ibrahim, et al. Clin Exp Rheumatol 2009;27:469–74; with permission.
Results of receiver operating characteristic curve analysis of the Psoriasis Epidemiology Screening Tool (PEST) and the Psoriatic Arthritis Questionnaire (PAQ) (Swedish modification).
The PEST questionnaire is a useful tool for screening for PsA in patients with psoriasis, but further validation and comparison with other tools is required. A study based in secondary care and comparing the PEST, ToPAS, and PASE tools is under way in the UK.
