Sensitivity of the Patient-Health Questionnaire (PHQ-9) items to change in three clinical trials in low- and middle-income countries.

Background: The 9-item Patient Health Questionnaire (PHQ-9) is a valid and widely used self-reported tool for assessing depressive symptoms. Although previous studies have demonstrated its sensitivity to change at the summary score level, there is limited investigation of the sensitivity of individual PHQ-9 items to change over time. This study aims to evaluate the sensitivity of PHQ-9 items to change using data from three separate samples.

Methods: Secondary analyses were conducted using longitudinal datasets from three randomized controlled trials in individuals with depression. Constrained and unconstrained longitudinal factor models of change were used to assess the sensitivity of PHQ-9 items. Multiple goodness-of-fit indices were used to assess the fit of the measurement models to each dataset.

Results: The PHQ-9 items were generally sensitive to detecting change over time across the three datasets. In the first dataset, the magnitude of the factor loadings associated with change over time ranged between 0.54 and 0.93; item 2 (depressive mood) was the most sensitive to change. In the other two datasets, the magnitude of the factor loadings associated with change over time ranged between 0.18 and 0.87; item 1 (anhedonia) was most sensitive to change, with item 2 (depressive mood) being a close second. Item 9 (suicidality) was the least sensitive to change across the three datasets.

Conclusion: The PHQ-2 items are sensitive to detecting within-person change in depressive symptoms over time across all three trials and are thus appropriate for assessing changes in depressive symptoms in research and clinical practice.