Acetylsalicylic acid (aspirin) test for the diagnosis of renovascular hypertension.

Objective: To determine whether the administration of acetylsalicylic acid (ASA, also known as Aspirin) differentiates patients with renovascular hypertension from those with essential hypertension, in order to provide a simple alternative to more expensive forms of diagnosis for this condition.
Design: Trial of ASA test in patients with previously diagnosed essential and renovascular hypertension.
Setting: Inpatient department of an academic health sciences centre in Poznan, Poland.
Patients: Forty patients with essential hypertension and 21 patients with renovascular hypertension.
Interventions: Patients were given an intravenous injection of ASA (10 mg/kg body weight), blood pressure was measured and blood was sampled and assayed for plasma renin activity (PRA) before and 30 minutes after the injection.
Results: ASA infusion in patients with renovascular hypertension resulted in a decrease in PRA from 15.2 (standard deviation [SD] 12.4) ng/mL per hour to 7.2 (SD 9.8) ng/mL per hour, whereas in patients with essential hypertension the initial PRA was significantly lower before ASA administration and did not change afterward. In patients with renovascular hypertension, the mean systolic, diastolic and arterial pressure decreased significantly (p < 0.001) after ASA infusion, but these did not change in patients with essential hypertension. Based on the criterion of 4 mm Hg as a detectable decrease in mean blood pressure, the sensitivity of the ASA test was 95.0% and the specificity 82.5%; its positive predictive value was 74% and its negative predictive value 97%.
Conclusion: The precise measurement of blood pressure during the ASA test may provide a useful method of differentiating between patients with renovascular and essential hypertension.