The Quality of Life in hand eczema questionnaire: validation of a new assessment instrument

Abstract

Background: Health related Quality of Life (HRQOL) is a patient reported outcome (PRO) used to evaluate clinical trials in various diseases. Health economic decisions are often based on HRQOL data, especially where the disease of interest is a chronic non life-threatening condition. Since there is no disease-specific HRQOL instrument to assess the impairments of patients with hand eczema (HE) we set out to develop an instrument to assess HE-specific HRQOL. The development process was done in an international group in order to receive an instrument which works in a culturally equivalent manner in different countries. Here we present the validation study of the German language version of the Quality of Life in hand eczema Questionnaire (QOLHEQ). Methods: The QOLHEQ was assessed up to three times in n = 316 HE patients. To explore construct validity we additionally assessed dermatology-specific (Dermatology Life Quality Index (DLQI) and Skindex-17) and generic (EuroQol -5 Dimensions (EQ -5D) HRQOL-instruments, a physician global assessment (PGA) of the HE and the disease severity as rated by the patient. The psychometric properties of the QOLHEQ were assessed using the Rasch model for each of the four subscales (symptoms, emotions, functioning and treatment/prevention) and a structural equation model to confirm the multi-dimensional structure of the QOLHEQ. We used several indices to test the responsiveness ofthe instrument. The analyses were done using AMOS 20, SPSS 20 and Rumm2030, Results: The study population was aged18 to 81 years (Mean: 46.7, SD 12.9), 45.9% were males. The PGA was normally distributed across the sample. After minor adaptations in the coding of two items all four subscales showed neither violations nor significant misfit to the Rasch model. The data revealed also a good fit to the structural equation model with HRQOL as primary construct and the four subscales as 2nd order factors. As expected the QOLHEQ showed a strong correlation with the dermatology-specific instruments (DLQI: r = 0.75 Skindex-17: r = 0.85) and a medium correlation with the EQ-5D (r =-0.51), the PGA (r = 0.34) and the disease severity reported by the patient (r = 0.59). The sensitivity to change of the QOLHEQ was superior compared with the other HRQOL-instruments as indicated by various responsiveness indices. Discussion: We have successfully developed and validated a diseases-specific HRQOL-instrument for HE. The QOLHEQ consists of 30 items assessing four relevant domains of HRQOL in HE patients and is ready to use in the German version. It's psychometric properties and responsiveness make it superior in assessing HRQOL in HE patients compared to other skin-disease specific or generic instruments. Other language versions (English, Danish, Finish, Japanese, Swedish and Turkish) will be available soon enabling scientists to compare their HRQOL data across countries.