The PHQ-9 Item 9 based screening for suicide risk: a validation study of the Patient Health Questionnaire (PHQ)−9 Item 9 with the Columbia Suicide Severity Rating Scale (C-SSRS)

Background: Item 9 of the Patient Health Questionnaire (PHQ) evaluates passive thoughts of death or self-injury within the last two weeks, and is often used to screen depressed patients for suicide risk. We aimed to validate the PHQ-9 item 9 with a brief electronic version of the Columbia Suicide Severity Rating Scale (eC-SSRS). Methods: We analyzed data from 841 patients enrolled in the National Network of Depression Centers Clinical Care Registry. We performed a validation analysis of PHQ-9 item 9 for suicide risk and ideation, using the eC-SSRS as a gold standard (defined as positive response to suicidal ideation with intent to act or recent suicidal behavior). Results: Of the 841 patients, 13.4% and 41.1% were assessed as being positive for suicide risk by the eC-SSRS and PHQ-9 item 9, respectively. For the overall cohort, sensitivity was 87.6% (95%CI 80.2–92.5%), specificity was 66.1% (95%CI 62.6–69.4%), PPV was 28.6% (95%CI 24.1–33.6%), and NPV was 97.2% (95%CI 95.3–98.3%) for the PHQ-9 suicide item. These performance measures varied within subgroups defined by demographic and clinical characteristics. In addition, the validity of PHQ-9 item 9 (cutoff score of 1) with eC-SSRS-defined suicide ideation showed overall poor results. Limitations: The gold standard used in our study was a surrogate measure of suicidality based on eC-SSRS scores. Conclusions: The results of our study suggest that item 9 of the PHQ-9 is an insufficient assessment tool for suicide risk and suicide ideation, with limited utility in certain demographic and clinical subgroups that requires further investigation.