Twenty‐Four–Hour Urine α₁‐Microglobulin as a Marker of Hypertension‐Induced Renal Impairment and Its Response on Different Blood Pressure–Lowering Drugs

The purpose of this study was to assess the role of urine α 1 ‐microglobulin as a marker of hypertension‐induced renal damage compared with estimated glomerular filtration rate, ( eGFR ), urine albumin, and urine albumin‐to‐creatinine ratio ( ACR ). Its response on different blood pressure (BP)– lowering drugs was also studied. Sixty never‐treated hypertensive patients (65.0% men, 46.9 years, BP 141.4/94.0 mm Hg) were randomized to an irbesartan (an angiotensin receptor blocker [ ARB] ) or a diltiazem (a nondihydropyridine calcium channel blocker [ CCB ])‐based regimen. Patients with diabetes or established cardiovascular, renal, or liver disease were excluded. Blood samples and 24‐hour urine were analyzed at baseline and 6 months after pharmaceutical BP normalization. Serum creatinine was measured and eGFR was calculated. Urine albumin, creatinine, and α 1 ‐microglobulin were measured and ACR was calculated. Minor changes ( P = not significant [NS] ) in eGFR were noted during follow‐up in both groups (from 111.0 mL /min/1.73 m 2 to 108.4 mL /min/1.73 m 2 in the ARB group and from 111.3 mL /min/1.73 m 2 to 114.0 mL /min/1.73 m 2 in the CCB group). Twenty‐four–hour urine indices were all significantly improved ( P <.01) in the ARB group (albumin from 19.4 mg/L to 8.2 mg/L, ACR from 21.5 mg/g to 10.0 mg/g, α 1 ‐microglobulin from 5.06 mg/L to 3.64 mg/L) but not ( P = NS ) in the CCB group (albumin from 15.6 mg/L to 13.9 mg/L, ACR from 17.6 mg/g to 17.1 mg/g, α 1 ‐microglobulin from 4.94 mg/L to 4.79 mg/L). These differences between groups remained significant ( P <.05) after adjusting for office heart rate and BP . α 1 ‐Microglobulin was significantly correlated ( P <.05) with albumin and ACR both at baseline ( r =0.283 and 0.299, respectively) and at the end of follow‐up ( r =0.432 and 0.465, respectively) but not ( P = NS ) with eGFR . It was also significantly related ( P <.05) to cardiovascular risk scores (Framingham and HeartScore) both at baseline ( r =0.264 and 0.436, respectively) and at the end of follow‐up ( r =0.308 and 0.472, respectively). Urine α 1 ‐microglobulin emerges as a potentially usable marker of hypertension‐induced renal impairment. Its excretion rate and its response to treatment appears similar to that of albumin. Irbesartan but not diltiazem seems to be associated with reduced excretion of α 1 ‐microglobulin in urine.