Test Characteristics of Urine Dipstick for Identifying Renal Insufficiency in Patients with Diabetes

OBJECTIVE: To evaluate the test characteristics of the urine dipstick as a screening tool for elevated serum creatinine in patients with uncontrolled diabetes mellitus in the emergency department (ED). METHODS: Patients with diabetes over the age of 18 who presented to the ED for any complaint over a three-month study period were considered eligible for participation in this study. A finger-stick blood glucose of ≥250 mg/dL at triage was used to confirm the diagnosis of uncontrolled diabetes. After obtaining written consent, each patient had a urine dip performed and a chemistry panel drawn. Any level of proteinuria on the urine dip was considered to be a positive test. Based on the laboratory and clinical guidelines at our institution, renal insufficiency was defined as creatinine concentration of greater than 1.3 mg/dL. RESULTS: Three Hundred ninety-three confirmed patients with uncontrolled diabetes were enrolled in this study, and 49 of these (12.5%) were found to have renal insufficiency. The sensitivity and specificity of the urine dip for predicting renal insufficiency were 69.4% (95% confidence interval [CI] 54.6–81.7%) and 57.8% (95%CI 52.4–63.1%) respectively. The positive predictive value was 19% (95%CI 13.5–25.5%), and the negative predictive value was 93% (95%CI 88.7–96%). The positive likelihood ratio was 1.65 (95%CI 1.32–2.06) and the negative likelihood ratio was 0.53 (95%CI 0.34–0.81). CONCLUSION: In this cohort of patients with uncontrolled diabetes, the test characteristics of the urine dipstick make it a poor screening tool for renal insufficiency in the ED.