Reverse white-coat effect as an independent risk for microalbuminuria in treated hypertensive patients.

Background: The influence of the converse phenomenon of white-coat hypertension called 'reverse white-coat hypertension' or 'masked hypertension' on hypertensive target organ damage has not been fully elucidated. The present study assessed the hypothesis that this phenomenon may specifically associate with microalbuminuria, a marker of early renal damage, in treated hypertension.

Methods: A total of 267 treated essential hypertensive patients (133 men and 134 women; mean age, 66 years) without renal insufficiency or macroalbuminuria were enrolled in this study. Patients were classified into three groups by the difference between office and day-time ambulatory systolic blood pressure (BP) levels; i.e. subjects with white-coat effect (W group: office--day-time systolic BP > or =20 mmHg, n = 48), with reverse white-coat effect (R group: office - day-time systolic BP < - 10 mmHg, n = 43) and without white-coat or reverse white-coat effect (N group: -10 mmHg < or = office--day-time systolic BP <20 mmHg, n = 176). The urinary albumin (U-Alb) level was measured as the albumin to creatinine excretion ratio in the urine. Microalbuminuria was defined as U-Alb of > or =30 and <300 mg/g Cr.

Results: R group had a well-controlled office BP (130/77 mmHg), but their day-time BP (148/87 mmHg) was elevated compared with the other two groups. The levels of U-Alb excretion in N group, W group and R group were 12.3 (8.4, 25.6), 16.0 (10.5, 31.7) and 24.3 (10.2, 79.7) mg/g Cr [median (interquartile range)], respectively. Both U-Alb level and prevalence of microalbuminuria were significantly greater in R group than in N group. Multivariate analyses revealed that the presence of reverse white-coat effect, but not white-coat effect, was a significant predictor for microalbuminuria, independent of various clinical variables including ambulatory BP levels (odds ratio 2.63 vs N group, P = 0.02).

Conclusion: These findings suggest that the presence of reverse white-coat effect may be an independent risk for early renal damage in treated hypertensive patients.