NT-Pro BNP: biomarker for monitoring of clinical status and as a prognostic marker in ambulatory patients with systolic heart failure

Introduction. The natriuretic peptides (BNP and NT-proBNP) represent a tool of considerable value in the context of heart failure (HF). The aim of this study was to evaluate the utility of NT-proBNP for monitoring of clinical status and as a prognostic biomarker in ambulatory patients with systolic heart failure (SHF) setting a cutoff value that enable us to predict the risk of adverse events. Methods. An analytic and prospective longitudinal study of a cohort of 74 patients with SHF (left ventricular ejection fraction, LVEF <40%) from the Multidisciplinary Heart Failure Unit was performed. The study was carried out in two different analytic stages separated by a 18 month-follow-up period. At each visit a doctor's care area appropriated the patient's clinical status, the determination of NT-proBNP blood values and the calculation of LVEF by echocardiography at the first visit (t0) and evolution (t1). Variables were analyzed: functional class (FC), LVEF and concentration of NT-proBNP at baseline (t0) and evolution (t1), and the relationship between them, and the development of adverse events during the follow-up. To determine the cutoff point were calculated measures of sensitivity and specificity by using ROC curves. Results. A relationship between progressively higher NT-proBNP values and the degree CF was observed. The mean value of NT-proBNP (pg/ml) for patients with LVEF < 35% was 1700.8 +/- 168.2 pg/ml (t0) and 1313.0 +/- 169.0 pg/ml (t1), while for the group LVEF > 35% was 492.6 +/- 105.7 pg/ml (t0) and 607.4 +/- 107.9 pg/ml (t1), with value of p=0.000 and 0.001, respectively. The 50% of patients presented an adverse event during the followup. To the absence of adverse events mean NT-proBNP was 411.6 +/- 89.6 pg/ml (t0) and 368.6 +/- 59.2 pg/ml (t1), whereas the presence of adverse events was 1716.6 +/- 62.0 (t0) and 1382.1 +/- 152.3 (t1), with values of p = 0.000. Regarding the cutoff of NT-proBNP, it was shown that the value of 1000 pg/ml is statistically significant as a predictor of adverse events in patients with similar degree of HF and LVEF, with a sensibility of 91.9%, specificity of 78.4%, and false negative rate of 8.1% and false positive rate of 21.6%. Conclusion. This study confirms the evidence of the efficacy of NT-proBNP as a parameter for monitoring of clinical status in patients with SHF, highlighting the finding of a cut-off value of 1000 pg/ml as a predictor of adverse events with an acceptable sensibility and specificity.