Purpose: Elevation of the plasma level of B-type natriuretic peptide (BNP) is commonly seen in patients with chronic kidney disease (CKD), but its significance remains unclarified. We conducted a prospective study to evaluate the role of plasma BNP level as a predictive marker of renal outcome.
Methods: 237 patients with CKD stage 3, 4 not on dialysis were prospectively enrolled as a hospital cohort from August 2004 to December 2008. Combined renal endpoint was doubling of baseline serum creatinine or end-stage renal disease requiring dialysis. Endpoint free renal survival was calculated by Kaplan Meier analysis and compared by the log-rank test. We used Cox proportional hazards analysis to determine the independent predictor for renal outcome among the clinical data at the time of referral to a nephrologist. ROC analysis was used to determine the best cut-off value of plasma BNP level to predict the renal outcome.
Results: The mean follow-up period was 2.5 +/- 1.1 years. Median age was 65 years. Of the subjects, 65.8% were men and 37.9% had diabetes mellitus. Median serum creatinine level was 2.7 mg/dL. Plasma BNP level was significantly higher among 147 patients who reached the combined renal endpoint compared with 90 patients who did not (116.0 pg/mL vs 54.5 pg/mL, p<0.001). After adjustment with other established predictive factors of renal outcome, plasma BNP level was selected to be the strongest predictive marker for renal endpoint (Hazard ratio 1.173, 95%CI 1.000-1.376). The optimal cut-off value of plasma BNP level suggested by ROC analysis was 69.5 pg/mL. Patients with a plasma BNP level above the cut-off point revealed a significantly poor renal outcome compared with those with a plasma BNP level below the cut-off point.
Conclusions: The present study suggests that the plasma BNP level might be a predictive marker for renal outcome and a guide for management of cardio-renal interaction.