Association between albumin:creatinine ratio and 24-hour ambulatory blood pressure in essential hypertension

Abstract

Microalbuminuria (MAU) is often found in essential hypertension (EH) and represents a sign of renal and cardiovascular damage. In the present study, we aimed to look at the association between ambulatory blood pressure (BP) and urinary albumin excretion (UAE). We studied 140 patients aged 50.1 ± 11.6 years referred for 24-h ambulatory blood pressure monitoring (ABPM) and, separately, 46 untreated subjects with newly diagnosed EH. Urinary albumin excretion was evaluated by determination of the albumin-to-creatinine ratio (ACR) in the first voided morning urine sample taken the same day as the ABPM was started. According to the ACR, patients were categorized as having normoalbuminuria (ACR <1.5 mg/mmol), borderline MAU (1.5 ≤ ACR <3.0 mg/mmol), and overt MAU (ACR ≥3.0 mg/mmol). Mean ACR was significantly higher in hypertensive than normotensive individuals (2.17 ± 2.67 mg/mmol and 1.72 ± 2.97 mg/mmol, respectively, P = .012). Average 24-h, daytime and nighttime systolic BP and diastolic BP were lower in patients with normoalbuminuria than in the other two groups and did not differ among the two microalbuminuric groups. Univariate regression analysis showed a close relationship between ACR and ambulatory BP. Strong correlation between BP and ACR in the normoalbuminuric and borderline microalbuminuric range was also obtained in the group of 46 newly diagnosed hypertensive patients. In conclusion, the threshold level of ACR ≥3.0 mg/mmol currently used to define microalbuminuria may be not applicable to EH. Instead, a threshold level of ACR ≥1. 5 mg/mmol may be more appropriate.