Renal dysfunction, hemodialysis, and the NT-proBNP/BNP ratio.

To the Editor With great interest we read the article by Srisawasdi et al. 1 They found that the ratio between N-terminal (NT)-pro-B-natriuretic peptide (BNP) and BNP increases exponentially with the stage of renal disease. van Kimmenade et al, 2 however, suggested the NT-proBNP/BNP ratio increases only slightly and shows a linear trend. Their findings are used to support the hypothesis that BNP and NT-proBNP concentrations rely equally on the glomerular filtration rate and predominantly on cardiac diseases, rather than on renal clearance. 2,3 The findings by Srisawasdi et al 1 suggest otherwise, and they rightly advocate that renal dysfunction should be taken into account when interpreting the diagnostic and prognostic potential of NT-proBNP and BNP. Missing in the data from Srisawasdi et al 1 are the ratios in the patients with end-stage renal disease who were treated with hemodialysis. On reading the article by Srisawasdi et al, 1 we decided to take a look at the NT-proBNP/BNP ratios in a population of patients receiving long-term hemodialysis for whom we recently described cardiac biomarker concentrations 4 and their relationship with volume status. 5 The population consisted of 44 patients receiving long-term hemodialysis from whom blood samples were obtained before dialysis at the start of the study and subsequently every 2 months for a period of 6 months. To better compare our results with those in the aforementioned study, we give the results for patients who were in clinically stable condition during the study period (eg, with no acute worsening in condition). 4 After exclusion of hospitalized patients, our population consisted of 21 men and 11 women with an average age of 66 years and average time of receiving dialysis of 33 months. The patients were divided into groups without (n = 15) and with (n = 17) a history of cardiovascular disease, which was considered present when the patient had a previous myocardial infarction, had required coronary intervention (eg, percutaneous transluminal coronary angioplasty or coronary artery bypass grafting), or had congestive cardiac failure. More details about the population can be found elsewhere. 4,5 In ❚Figure 1❚, we summarize the NT-proBNP/BNP ratios measured during the 6-month study for each of the 32 patients (patients 16-32 have a history of cardiovascular disease). To clarify the results in Figure 1 and to foster understanding of the magnitude of the NT-proBNP/BNP ratios in this population, we mention that even patients with the lowest ratios, …