Convergent Validity of Suffering and Quality of Life as measured by The Hidradenitis Suppurativa Quality of Life

BACKGROUND Hidradenitis suppurativa (HS) is a painful chronic, recurrent inflammatory skin disease with great impact on health-related quality of life (HRQOL). Recently, Hidradenitis SuppuraTiva cORe outcomes set International Collaboration (HISTORIC) established HRQOL as a core domain set for HS clinical trials and developed the Hidradenitis Suppurativa Quality of Life (HiSQOL) as a validated outcome measurement instrument. OBJECTIVES To provide further convergent validity of HiSQOL by comparing it to Dermatology Life Quality Index (DLQI) and Pictorial Representation of Illness and Self Measure-Revised 2 (PRISM-R2). METHODS In this cross-sectional study, 103 participants completed HiSQOL, PRISM-R2 and DLQI. PRISM-R2 is an instrument designed to measure suffering and reports the two measures, Illness Perception Measure (IPM) and Self-Illness Separation (SIS). Correlation analyses were performed including a sub-analysis for a subgroup of patients with high scores in the HS-specific domains of HiSQOL. RESULTS A very strong correlation was found between HiSQOL and DLQI (ρ = 0.93, P < 2.2 × 10-16 , (95% CI: 0.89;0.95)), and moderately strong correlations were found between HiSQOL and SIS (ρ = -0.73, P < 2.2 × 10-16 , (95% CI: -0.81; -0.62)) and DLQI and SIS (ρ = -0.70, P < 2.2 × 10-16 , (95% CI: -0.79; -0.59)). IPM was positively associated with HiSQOL and DLQI and negatively with SIS. CONCLUSIONS HiSQOL is a valid measure of quality of life for HS patients, and we suggest that HiSQOL can be used as a measure of suffering as well.