Using a Type of Blood Pressure Medicine, Angiotensin-Converting Enzyme Inhibitors, To Prevent Worsening of Kidney Disease Unrelated to Diabetes

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The summary below is from the full report titled "Angiotensin-Converting Enzyme Inhibitors and Progression of Nondiabetic Renal Disease. A Meta-Analysis of Patient-Level Data." It is in the 17 July 2001 issue of Annals of Internal Medicine (volume 135, pages 73-87). The authors are TH Jafar, CH Schmid, M Landa, I Giatras, R Toto, G Remuzzi, G Maschio, BM Brenner, A Kamper, P Zucchelli, G Becker, A Himmelmann, K Bannister, P Landais, S Shahinfar, PE de Jong, D de Zeeuw, J Lau, and AS Levey, for the ACE Inhibition in Progressive Renal Disease Study Group.

What is the problem and what is known about it so far?

Angiotensin-converting enzyme (ACE) inhibitors are a type of medication used to treat high blood pressure. The ACE inhibitors have clearly been shown to prevent worsening of kidney disease caused by diabetes. Some studies suggest that ACE inhibitors benefit nondiabetic people with kidney disease, while other studies do not. More than 350,000 people in the United States have end-stage kidney disease and require either dialysis, a procedure that filters the blood through an artificial kidney machine, several times a week, or a kidney transplant to stay alive. It is important to know whether ACE inhibitors might prevent worsening of kidney disease and keep some people from needing dialysis and transplantation.

Why did the researchers do this particular study?

To find out whether ACE inhibitors prevent worsening of kidney disease when the kidney disease is not due to diabetes.

Who was studied?

The study included 1860 patients with kidney disease but no diabetes. The patients had participated in any of 11 previous studies. In these studies, patients had been randomly assigned to treatment with ACE inhibitors, another type of blood pressure medicine, or placebo. Placebos are substances that look like the medicine but contain no active ingredients.

How was the study done?

Rather than do a new study, the researchers combined data from all patients who had participated in previous smaller studies of ACE inhibitors in nondiabetic people with kidney disease. Combining studies in this manner is a technique called patient-level meta-analysis; this type of study can help answer questions when several smaller studies have conflicting results. The researchers measured blood pressure and the amount of protein in the urine and compared the results in patients who received ACE inhibitors with those in patients who received other blood pressure medicines or placebo. Larger amounts of protein in the urine indicate worse kidney disease.

What did the researchers find?

Kidney function was better preserved in patients who received ACE inhibitors than in patients who received other drugs or placebos. Patients who received ACE inhibitors also had greater decreases in both blood pressure and urine protein levels. However, better blood pressure control and lower urine protein levels in the people taking ACE inhibitors did not explain the kidney benefits.

What were the limitations of the study?

Patients were followed for an average of just over 2 years, so it is not known whether the benefit from ACE inhibitors is greater or smaller after longer periods of treatment. The study does not tell us whether ACE inhibitors benefit persons who have very mild kidney disease and no protein in the urine.

What are the implications of the study?

Angiotensin-converting enzyme inhibitors help prevent worsening of kidney disease that is unrelated to diabetes.