Measuring urine protein in blacks who have chronic kidney disease related to high blood pressure might help physicians slow the disease progression in some patients, a new study says.

The research, published in the Sept. 2 New England Journal of Medicine, found that lowering blood pressure below recommended goals delayed end-stage renal disease in blacks with a baseline urinary protein-to-creatinine ratio greater than 0.22. No benefit of aggressively decreasing blood pressure was seen in patients whose protein-to-creatinine ratio was 0.22 or less. Elevated levels of protein in urine indicate greater kidney damage.

“Here’s a group of patients where it’s worth the extra effort to put them on additional medication to get their blood pressure lower,” said lead study author Lawrence J. Appel, MD, MPH, professor of medicine, epidemiology and international health at Johns Hopkins University School of Medicine in Maryland.

“Kidney disease is a common problem, and it’s particularly prevalent in African-Americans. ... If we can delay it, that’s great,” he said.

Nearly 30 million Americans have CKD, according to the American Society of Nephrology. The disease is 15% more prevalent among blacks than whites. Blacks also are four times more likely to develop ESRD. About 30% of new ESRD cases are attributed to high blood pressure, according to the NEJM study (http://www.nejm.org/doi/full/10.1056/NEJMoa0910975).

Researchers examined data on 1,094 blacks age 18 to 70 with hypertensive CKD at 21 U.S. medical centers between February 1995 and June 2007. The study consisted of an initial trial phase, followed by a cohort phase.

In the trial phase, researchers randomly assigned 554 participants to receive standard blood pressure control and 540 to get more intensive control. In the standard control group, the blood pressure target was 140/90 mmHg. The target in the more intensive control group was 130/80 mmHg.

Researchers lowered patients’ blood pressure through a combination of medications.

Participants who were not diagnosed with ESRD were invited to enroll in the cohort phase of the study. These patients were switched from their randomized medications to ramipril, and their blood pressure target was less than 130/80 mmHg.

The study found that CKD progression occurred in 30% of patients during the trial phase and in 37% in the cohort phase. The low blood pressure target was no better than standard blood pressure treatment at slowing the progression of CKD among participants in both study phases.

The exceptions were patients in the more intensive control group whose baseline protein-to-creatinine ratio was greater than 0.22. Among these participants, the likelihood of ESRD was reduced by 25%.

Dr. Appel recommends that physicians check for protein in patients’ urine before determining the blood pressure target for blacks with CKD. If protein is present, a lower goal has the potential to slow the progression of the condition, he said.

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By Christine S. Moyer, amednews staff. Posted Sept. 17, 2010.