Cross-cultural validation of the PHQ-9 in Bahasa Indonesia to measure depression among persons affected by leprosy

Introduction
Although leprosy is curable since 1981, people affected by leprosy still experience stigmatisation and discrimination. The stigma towards people affected by leprosy may lead to a decreased quality of life. Few studies have focused on major depressive disorder as a comorbidity of leprosy. There is no simple and widely validated instrument that has been validated to diagnose depression among people affected by leprosy. For this study, the PHQ-9 was cross-culturally validated in Bahasa Indonesia. The PHQ-9 has been validated in other countries in Asia, however not in Indonesia or for people affected by leprosy.

Objective
The purpose of this study is to (A) perform a cultural validation of the PHQ-9 in Bahasa Indonesia and (B) to measure the depression status of people affected by leprosy with the validated PHQ-9.

Methods
This study took place in Central Java. The PHQ-9 was translated and back-translated and after that, 15 semi-structured interviews and one focus group were conducted for assessing the conceptual, operational, item and semantic equivalence. After analysing the interviews, a refined version of the PHQ-9 was made. For the quantitative part, 114 people affected by leprosy and 54 control group were included to assess the measurement equivalence. Forty-nine people repeated the questionnaire one week later. The following psychometric properties were calculated using SPSS: internal consistency, construct validity, reliability, floor and ceiling effects, interpretability, cut-off score and the prevalence of depression.

Results
Two questions were adapted and after that all questions were considered relevant, comfortable and clear. The internal consistency was defined with Cronbach’s alpha and 0.718. Floor and ceiling effects were not found. The reliability was measured with the repeated interviews. The intra-class coefficient was 0.713 (p<0.001). For the construct validity, the Spearman correlation showed that there was a positive correlation between the total score of the PHQ-9 and the total score of the BDI-II. The means and standard deviations of the people affected by leprosy group and the control group showed that the PHQ-9 was able to distinguish between groups defined by gender, leprosy-related physical problems and visible signs of leprosy. A cut-off point of 10 was adopted on the basis of the original validation of the PHQ-9. The results showed a higher prevalence of depression in the people affected by leprosy group, but this was not significant.

Conclusion
The PHQ-9 is suitable to be used as a screening instrument of depression for people affected by leprosy and in Indonesia. The item, semantic and measurement equivalence are good.