Capsule Commentary on Marc et al., Reliability and Validity of the Haitian Creole PHQ-9

This study by Marc et al.¹ developed and tested a Haitian-Creole translation of the PHQ-9 in men who have sex with men (MSM) living in the Republic of Haiti. The investigators demonstrated unidimensionality of the translated PHQ-9, moderately high internal consistency reliability (α=0.78), preliminary evidence of construct validity (i.e., greater depression in HIV-positive subjects), and no evidence of differential item functioning (DIF) across age, education, sexual orientation or HIV status.

The PHQ-9 has become one of the most widely-used depression measures due to its brevity, inclusion of the nine criteria for major depressive disorder (MDD), utility as a screening, severity, and outcome measure, and public domain status.² The PHQ-9 has been translated into more than 80 languages (many available at www.phqscreeners.com). Because it is difficult to obtain funding solely for translations, new translations of a measure are often developed as part of studies funded for other reasons (e.g., epidemiological research, multi-national pharmaceutical trials, or by investigators with an interest in conditions assessed principally by patient-report). Also, when a measure has already been widely translated, a publication validating a new translation has added value when it provides data on a new population (e.g., MSM) or “higher-level” psychometric analyses (e.g., factor analysis and DIF). Most studies examining the factor structure of the PHQ-9 have found it to be unidimensional; thus, even though MDD comprises several types of symptoms (e.g., somatic, affective, cognitive), it appears the MDD syndrome is captured by a single overarching construct. One implication is that the clinician need not decide if somatic symptoms are due to a comorbid medical disease or depression, but can use an inclusive approach to counting all symptoms towards a diagnosis of MDD.³ Fewer studies have examined DIF for the PHQ-9, and these have typically (but not invariably) shown that the PHQ-9 items perform similarly across most demographic and disease subgroups. Patient-reported outcome measures like the PHQ family of scales and the NIH PROMIS measures⁴ (www.nihpromis.org) are becoming increasingly important,⁵ and valid translations are necessary for evaluating and improving global health.