RF04: Seven important criteria for the diagnosis of psoriasis in children: the results of a large UK multicentre diagnostic accuracy study (DIPSOC study)

E. Burden-Teh,^1,2 R. Murphy,^1,3 S. Gran,¹ T. Nijsten,^1,4 C. Hughes,¹ A. Abdul-Wahab,⁵ A. Bewley,⁶ N. Burrows,⁷ S. Darne,⁸ J.E. Gach,⁹ R. Katugampola,¹⁰ C.S. Jury,¹¹ K.-H. Kuet,³ J. Llewellyn,¹ T. McPherson,¹² J. Ravenscroft,¹³ S. Taibjee,¹⁴ C. Wilkinson¹⁵ and K.S. Thomas¹

¹Centre of Evidence Based Dermatology, University of Nottingham, Nottingham, UK; ²Department of Dermatology, Nottingham University Hospitals NHS Trust, Nottingham, UK; ³Department of Dermatology, Sheffield Children’s NHS Foundation Trust, Sheffield, UK; ⁴Department of Dermatology, Erasmus MC, Rotterdam, The Netherlands; ⁵Department of Dermatology, St George’s University Hospitals NHS Foundation Trust, London, UK; ⁶Department of Dermatology, Barts Health NHS Trust, London, UK; ⁷Department of Dermatology, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK; ⁸Department of Dermatology, The James Cook University Hospital, Middlesbrough, UK; ⁹Department of Dermatology, University Hospitals Coventry and Warwickshire NHS Trust, Coventry, UK; ¹⁰Department of Dermatology, Cardiff and Vale University Health Board, Cardiff, UK; ¹¹Department of Dermatology, Royal Hospital for Children, Glasgow, UK; ¹²Department of Dermatology, Oxford University Hospitals NHS Foundation Trust, Oxford, UK; ¹³Department of Paediatric Dermatology, Nottingham University Hospitals NHS Trust, Nottingham, UK; ¹⁴Department of Dermatology, Dorset County Hospital NHS Foundation Trust, Dorchester, UK; and ¹⁵Department of Dermatology, University Hospital Plymouth NHS Trust, Plymouth, UK

In children, psoriasis can be challenging to diagnose. Difficulties arise from differences in the clinical presentation compared with adults, because other childhood rashes are common and because psoriasis may be an unexpected diagnosis. Case identification underpins clinical trials and epidemiological research, both of which are needed to advance treatment and inform advice given to children and families. A case–control diagnostic accuracy study in 12 UK paediatric dermatology departments was undertaken between 2017 and 2019 [Developing Diagnostic Criteria for Psoriasis in Children (DIPSOC study)]. Eighteen clinical criteria agreed in an eDelphi consensus study involving the International Psoriasis Council were assessed by trained investigators who were blinded to the participant’s diagnosis. The primary objective of the study was to test the diagnostic accuracy (sensitivity and specificity) of (i) the consensus-agreed criteria and (ii) the best predictive diagnostic criteria (determined using backward logistic regression). Children (aged < 18 years) diagnosed by a dermatologist with psoriasis (160 cases) or a different scaly inflammatory rash (170 controls) were recruited. Both new and follow-up patients were included. Participants were, on average (SD), 9·3 (4·7) years and 70% were of white ethnicity. One-third (32%) were new consultations, and in 36% the disease severity was recorded as moderate or severe. Nearly all controls had eczema (95%). The sensitivity of the consensus agreed criteria and scoring algorithm (one major and/or three or more minor criteria) was 84·4%, specificity was 65·1% and area under the curve (AUC) was 0·75 (95% confidence interval 0·70–0·80). The seven diagnostic criteria that performed best were (i) scale and erythema in the scalp involving the hairline [odds ratio (OR) 2·17]; (ii) scaly erythema inside the external auditory meatus (OR 2·05); (iii) persistent well-demarcated erythematous rash anywhere on the body (OR 2·79); (iv) scaly erythematous plaques on the extensor surfaces of the elbows and knees (OR 2·01); (v) persistent erythema in the umbilicus (OR 3·06), (vi) well-demarcated erythematous rash in the napkin area involving the crural folds (OR 2·66); and (vii) family history of psoriasis (OR 3·66). The sensitivity of the best predictive model using the development cohort was 76·8%, specificity was 72·7% and AUC was 0·84 (95% CI 0·79–0·88). This study provides examination-based data on the clinical features of psoriasis in children. The results highlight the importance of scalp, auricular, umbilical and napkin involvement in children – sites that may be hidden by hair and clothing. Seven diagnostic criteria with good discriminatory ability in secondary-care patients are identified, which will inform further planned validation studies.