Cross-cultural validation of the Patient Health Questionnaire (PHQ-9) and the Mental Wellbeing Scale (WEMWBS) among people affected by lymphatic filariasis, in India.

Introduction: Lymphatic filariasis (LF) is considered to be the main cause of long-term physical disability worldwide according to the World Health Organization. LF causes physical, psychological, and social suffering. It is important to quantify the severity of the disability due to the disease in order to implement and evaluate morbidity management and stigma reduction programs. Until now, no instruments have been validated to measure depression and mental wellbeing as comorbidity of LF in India.

Objective: To cross-culturally validate the Patient Health Questionnaire (PHQ-9) and the Mental Wellbeing Scale (WEMWBS) among people affected by LF-related lymphedema, in India.

Methods: A cross-sectional mix methods study design was used. For the cross-cultural validation of the two scales, the cultural equivalence framework was used. First, a small qualitative pilot study was performed, for assessing the semantic, conceptual, item, and operational equivalences, through semi-structured interviewing. After that, the scales were quantitively validated. For this measurement equivalence was assessed through structured interviewing. Here, four psychometric properties were tested namely: interpretability, floor and ceiling effects, construct validity and interpretability.

Results: The qualitative study included eight participants affected by LF. Both the PHQ-9 and WEMWBS showed adequate conceptual and item equivalence. To improve semantic and operational equivalence, adjustments were made in both scales and all statements were changed into questions. The quantitative study included 101 cases and 62 controls. This study showed that both scales had excellent psychometric properties. Internal consistency of the PHQ-9 and WEMWBS was high (Cronbach’s α: 0.86 and 0.86), construct validity was supported, no floor and ceiling effects were found and appropriate median values have been given to aid interpretability of the scores.

Conclusion: After making some adjustments, the PHQ-9 and WEMWBS are considered culturally valid in Jharkhand and similar Hindi-speaking settings among people affected by LF-related lymphedema to measure depression and mental wellbeing.