Urine Dipstick as a Screening Test for Serum Creatinine Elevation in Emergency Department Patients with Severe Hypertension

OBJECTIVE: Patients presenting to the emergency department (ED) with severe hypertension require assessment for acute end-organ damage. Serum creatinine (SCr) measurement is routinely recommended to detect renal dysfunction. The authors assessed the utility of the urine dipstick test in screening for acute SCr elevation in this population. METHODS: The authors performed a prospective study of adult ED patients with diastolic blood pressures > or = 115 mm Hg that persisted for > or = 30 minutes or necessitated emergent treatment. Excluded were menstruating and pregnant women and patients with urinary infection, trauma, or dialysis dependence. Patients reporting a history of renal disease were excluded if the SCr was abnormal and no baseline value was available. Each subject had an SCr and urine dipstick test. The authors examined the performance of the dipstick in identifying an elevated SCr, defined as SCr > 1.2 mg/dL or > 25% above baseline. RESULTS: Of 143 patients, 42 had SCr > 1.2 mg/dL. Eighteen reported prior renal disease but had an SCr that was normal or < or = 25% above baseline. The remaining 24 subjects comprised the elevated SCr group. The presence of either proteinuria or hematuria on dipstick identified these patients with 100% sensitivity and 29.7% specificity. Specificity rose to 42.4% without loss of sensitivity when an abnormal dipstick was defined as hematuria or > or = 1+ proteinuria. CONCLUSIONS: The urine dipstick may be an effective screening test for SCr elevation in patients with severe hypertension. A restrictive definition of an abnormal dipstick would identify all patients with elevated SCr and substantially reduce the number of SCr assays necessary.