Measuring Depression-Severity in Critically Ill Patients' Families with the Patient Health Questionnaire (PHQ): Tests for Unidimensionality and Longitudinal Measurement Invariance, with Implications for CONSORT

The longer eight- and nine-item PHQ scores appear inappropriate for assessing depression severity in this population, with constructs based on smaller subsets of items being more promising targets for future trials. The Consolidated Standards of Reporting Trials requirement for prespecified trial outcomes is problematic because unidimensionality/invariance testing must occur after trial completion. Consolidated Standards of Reporting Trials could be strengthened by endorsing rigorous assessment of composite scores and encouraging use of the most appropriate substitute, should trial-based evidence challenge the legitimacy of prespecified multi-item scores.