NEW YORK (Reuters Health) – Ambulatory blood pressure monitoring (ABPM) is a better predictor of renal and cardiovascular events than office BP measurement in patients with chronic kidney disease (CKD) not yet on dialysis, according to results of a study. Measuring BP in the office was not helpful in this regard.

Dr. Roberto Minutolo, of the Second University of Naples, Italy, and colleagues report their study in the June 27 issue of Archives of Internal Medicine.

“Our study suggests that using ABPM clinicians may provide to patients with CKD more precise prognostic information on their risk of experiencing a cardiovascular accident or reaching end-stage renal disease,” Dr. Minutolo noted in an e-mail to Reuters Health.

“With this technique, we can measure BP during nighttime and so identify those patients with nocturnal hypertension, who are at greatest risk for renal progression and fatal or non fatal cardiovascular accident. In our center, we perform ABPM annually in all CKD patients with hypertension,” he added.

The prospective cohort study involved 436 patients with CKD from four nephrology clinics in Italy. During a morning office visit, each patient’s BP was measured three times and they were outfitted with an ABPM that took readings every 15 minutes during the day and every half hour overnight. The patients returned to the office the next morning where their BP was measured again.

The mean age of study patients was 65 years, 42% were women, 37% had diabetes and 31% had cardiovascular disease. The mean glomerular filtration rate for the cohort was 42.9 mL/min/1.73 m2 (squared). The primary end points were renal death (end-stage renal disease or death) and cardiovascular events.

During a median followup of 4.2 years, 86 patients progressed to end-stage renal disease and 69 patients died. The researchers also recorded 63 nonfatal cardiovascular events and 52 cardiovascular deaths.

Patients with daytime systolic BP in the range of 136 to 146 mm Hg and > 146 mm Hg had a 2.23-fold and 3.07-fold increased adjusted risk, respectively, of cardiovascular events during follow up. These two quintiles were also associated with a greater risk of renal death, with hazard ratios of 1.72 and 1.85, respectively.

Similarly, patients with the highest daytime diastolic BP (> 84 mm Hg) had a 2.55-fold increased risk of cardiovascular events and a 2.67-fold increased risk of renal death.

Nighttime readings of systolic BP between 125 to 137 mm Hg was associated with a 2.52-fold increased risk of cardiovascular events; a nighttime systolic BP > 137 mm Hg was associated with a 4-fold increased risk of cardiovascular events. For renal death, the corresponding hazard ratios were 1.87 and 2.54.

Nighttime diastolic BP in the range of 70 to 75 mm Hg or > 75 increased the risk of cardiovascular events by 2.00 and 2.38-fold, respectively, and renal death by 1.48- and 1.81-fold, respectively.

In contrast, office BP measurement (either systolic BP or diastolic BP) did not predict cardiovascular or renal events.

“Performing ABPM in patients with CKD adds the nephrologists’ ability to predict hard end points, over clinic BP,” Dr. Minutolo told Reuters Health. “Interestingly, blood pressure measured in office was not able to predict renal or cardiovascular events.”

The researchers also observed a significantly greater risk of both study end points in nondipper and reverse dipper subgroups.

Dr. David Goldsmith from King’s Health Partners AHSC in London, England, and Dr. Adrian Covic, from C.I. Parhon University Hospital in Iasi, Romania comment on the study in a linked commentary.

In their article, they note that ABPM is “currently recommended by most authorities and guideline groups only for patients with symptomatic or unpredictable BP, and home BP measurement is acknowledged as another valid approach.”

“We believe that there are selected cohorts of patients in whom the additional time, effort, and expense of doing ABPM is justified, and this new study by Minutolo and colleagues makes that case stronger for our patients with CKD,” they write.

“It is now harder to defend reliance on clinic BP measurement alone if we nephrologists are serious about targeted BP intervention,” Dr. Goldsmith and Dr. Covic conclude.

Arch Intern Med 2011;171:1090-1099.