Validation of the telephone-administered PHQ-9 against the in-person administered SCID-I major depression module

Background: We assessed item-to-item correspondence between the Patient Health Questionnaire-9 (PHQ-9) and the Structured Clinical Interview for DSM-IV Axis I Disorders (SCID-I) major depression episode portion of the major depressive module. Method: Four hundred and ninety-eight soldiers in the Ohio National Guard were administered the PHQ-9 and SCID-I. Data were analyzed using chi-square analyses, logistic regression, receiver operating characteristic (ROC) curve analyses and diagnostic efficiency statistics. Results: To screen for depression effectively, results indicate use of the cardinal first two items, items representing fatigue, appetite and sleep changes with an item level cut-off point of two, and the item representing suicidal ideation with item level cut-off point of one. Further, total PHQ-9 scores significantly predicted SCID-I major depressive episode (MDE) and diagnosis (MDD) with moderate accuracy. Lastly, the cut-off total score of 10 had the optimal balance of sensitivity and specificity compared to other PHQ-9 scoring options. Limitations: Differences in timeline of administration of the measures, differences in "worst episode" reference between the measures, and use of a specific military population are some of the limitations. Conclusions: This validation study provides guidelines for the use of the telephone-administered PHQ-9 in assessing the lifetime prevalence of a major depressive episode and diagnosis in non-clinical populations, with implications for clinical use.