Comparing the Beck Depression Inventory-II (BDI-II) and Patient Health Questionnaire (PHQ-9) Depression Measures in an Outpatient Bariatric Clinic

Background: Screening for depressive symptoms is important when evaluating bariatric surgery candidates, as worse outcomes can be seen with higher pre-surgical and post-surgical psychiatric comorbidities. The Beck Depression Inventory-II (BDI-II) and Patient Health Questionnaire (PHQ-9) are two widely used depression screening instruments. This study evaluated whether both instruments have similar performance in an outpatient bariatric surgery clinic setting. Methods: One thousand thirty-four bariatric surgery candidates completed both PHQ-9 and BDI-II whose scores were analyzed in this retrospective study. Spearman’s correlation coefficient was calculated to compare total scores on each instrument. PHQ-9 categories were compared to corresponding BDI-II categories via several different methods. Weighted kappa coefficients were calculated for (1) PHQ-9 and BDI-II categories, (2) scores ≥10 on the PHQ-9 and ≥20 on the BDI-II, and (3) the specific item of suicidality. Results: Spearman’s correlation was strong at 0.74. The median PHQ-9 and BDI-II scores were 5 and 9, corresponding to the mild and minimal categories, respectively. Weighted kappa analysis demonstrated a moderate association between depressive symptom categories evaluated using three methods. A moderate to substantial association was found for the suicidality item, with agreement of 92.3 %. Conclusions: PHQ-9 and BDI-II scores in patients seeking bariatric surgery are closely correlated. Categories of depressive symptom severity and responses to suicidality showed moderate to substantial agreement. When choosing an appropriate depression screening tool, these findings support the use of the PHQ-9 as a viable alternative to the BDI-II in patients seeking bariatric surgery.