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.