PS05: The role of disease severity and illness perceptions in predicting health outcomes in people with hidradenitis suppurativa: a longitudinal study

Abstract

The role of disease severity and illness perceptions in predicting health outcomes in people with hidradenitis suppurativa: a longitudinal study K. Jones, A.P. Blanco, E. Rashid, F. Ferguson, J. Weinman and M. Turner King’s College London, Institute of Psychiatry, London, UK and St John’s Institute of Dermatology, Guy’s and St Thomas’ NHS Foundation Trust, London, UK Hidradenitis suppurativa (HS) is a chronic inflammatory skin disease that affects apocrine gland-bearing skin. It is characterized by inflamed nodules and abscesses that develop into sinus tracts and subsequent scarring. Research has found high rates of anxiety, depression and impaired quality of life (QoL) in people with HS. These outcomes have been linked to psychosocial and clinical factors, including how people perceive their illness (illness perceptions) and disease severity. One HS study found that illness perceptions were more strongly related to outcomes than disease severity; however, research has not explored the predictive utility of these factors in longitudinal design. The first aim was to examine whether illness perceptions at baseline predict QoL and symptoms of anxiety and depression over time, independently of disease severity. The second aim was to investigate the stability of illness perceptions over time, and whether this is associated with health outcomes. This was a longitudinal study of 135 participants with HS in a tertiary service. The Brief Illness Perceptions Questionnaire, Generalized Anxiety Disorder-2, Patient’s Health Questionnaire-2, Dermatology Life Quality Index and a pain visual analogue scale were completed at two timepoints (average duration between these was 8 83 months). Disease severity was assessed by dermatologists using the Hurley staging system. Multiple regressions indicated that, over time, illness perceptions explained an additional 13 7% of variance in anxiety symptoms (P < 0 05), 11 2% in depression symptoms (P < 0 05) and 12 1% in QoL (P < 0 01) over and above demographic and clinical factors, including disease severity. HS severity did not significantly increase the variance explained in health outcomes over time. Friedman’s two-way ANOVA by ranks and Wilcoxon signed rank tests indicated that illness perceptions were stable over time, apart from beliefs about identity and concern, which decreased (P <0 05). Spearman’s rho correlation coefficients showed that reductions in negative beliefs about consequences, timeline, personal control and concern were associated with improved health outcomes. Overall, illness perceptions were better predictors of QoL and symptoms of anxiety and depression over time than disease severity, and most perceptions remained stable. This illustrates the importance of assessing illness perceptions, anxiety, depression and QoL as routine aspects of HS multidisciplinary care, with the development of pathways into services targeting depression and anxiety being of key importance. Future research could replicate this study using a dynamic severity measure, as Hurley stage only measures static features. Research is also required to develop interventions for modifying illness perceptions alongside dermatological treatment.