The BDI and the SF36: which tool to use to screen for depression?

Recent studies have suggested a relationship between depression--as assessed by the Beck Depression Inventory (BDI)--and mortality in end-stage renal disease (ESRD) patients. A recent study from the Dialysis Outcomes and Practice Patterns Study (DOPPS) indicated an association between mortality in a large cohort of hemodialysis patients and the patients' responses in the preceding 4 weeks to two questions on the Kidney Disease Quality of Life, Short Form (KDQOL-SF36): "Have you felt downhearted and blue?" and "Have you felt so down in the dumps that nothing could cheer you?" A BDI score > or = 11 and a score < or = 3 for the two questions on the SF36 were considered to suggest the presence of depressive symptoms; both scores have been associated with increased mortality in hemodialysis patients. We aimed to examine the relationship of the two SF36 questions with depressive symptoms as assessed by the BDI. All patients on chronic peritoneal dialysis (CPD) therapy and daily hemodialysis therapy in our units between June 2000 and January 2002 were asked to complete a BDI and an SF36. We recorded 135 tests in 80 CPD patients, and 76 tests in 17 daily hemodialysis patients. Correlation coefficients (r2 values) of the responses to the two questions on the SF36 and the BDI scores demonstrated a significant relationship between the scores. The r2 values for the CPD patients' two SF36 responses and the BDI scores were -0.622 and -0.506; the r2 values for the daily hemodialysis patients were -0.363 and -0.317. The sensitivity and specificity for each SF36 response to be < or = 3 when the BDI was > or = 11 were 82.4% and 68.6% for the "downhearted and blue" question and 65% and 67% for the "down in the dumps" question. Whether the two questions on the SF36 that suggest depression can replace the BDI as a screening tool requires further study. Furthermore, it is unclear if the two questions on the SF36 are predictive of mortality because of their association with clinical depression or because of other issues.