In Reply: The Role of NT-proBNP as a Prognostic Marker in Pulmonary Hypertension

Abstract

We thank very much Dr. Souza et al for their interest in our article (May 2006) 1 Fijalkowska A Kurzyna M Torbicki A et al. Serum N-terminal brain natriuretic peptide as a prognostic parameter in patients with pulmonary hypertension. Chest. 2006; 129: 1313-1321 Abstract Full Text Full Text PDF PubMed Scopus (331) Google Scholar on the potential clinical role of N-terminal-pro-brain natriuretic peptide (NT-proBNP) estimation in patients with pulmonary arterial hypertension (PAH). We also agree with their concerns regarding the universal validity of the prognostic cutoff values that were reported in our article. Clearly, with a study group of slightly > 50 patients we would not impose or recommend such values for universal prognostic use. Furthermore, we do not believe that even the most sophisticated statistical analysis could extract more objective truth from such a database. On the other hand, by looking at the receiving operating characteristic analysis and trying to identify prognostic thresholds we wanted to avoid the common practice of reporting the prognostic significance of median values. While highly dependent on the initial characteristics of the study group of the index trial, such median values later often become surprisingly “magic numbers” and are extrapolated to other populations with even less evidence. This was the case both for a 6-min walk test distance of 332 m or an NT-proBNP concentration of 150 pg/L as a result of the reports of Nagaya et al 2 Nagaya N Nishikimi T Uematsu M et al. Plasma brain natriuretic peptide as a prognostic indicator in patients with primary pulmonary hypertension. Circulation. 2000; 102: 865-870 Crossref PubMed Scopus (713) Google Scholar and Miyamoto et al. 3 Miyamoto S Nagaya N Satoh T et al. Clinical correlates and prognostic significance of six-minute walk test in patients with primary pulmonary hypertension: comparison with cardiopulmonary exercise testing. Am J Respir Crit Care Med. 2000; 161: 487-492 Crossref PubMed Scopus (957) Google Scholar Therefore, rather than defending our 1,400 and 3,400 pg/L thresholds, even though they were derived from a receiving operating characteristic analysis, we would reply by issuing a call for pulling together data on PAH patients whose baseline clinical characteristics and NT-proBNP concentrations were tested with a method similar to the one used in our study. This may be true, for instance, for the study population of a trial recently published by Souza et al. 4 Souza R Bogossian HB Humbert M et al. N-terminal-pro-brain natriuretic peptide as a haemodynamic marker in idiopathic pulmonary arterial hypertension. Eur Respir J. 2005; 25: 509-513 Crossref PubMed Scopus (50) Google Scholar We have recently witnessed a great step forward in the understanding of the efficacy of the new drugs developed for the treatment of PAH thanks to global collaboration between expert centers. It is time to try to start building networks of collaboration to learn more about prognostic indexes and clinical end points. We would be available for this type of collaboration. The Role of NT-proBNP as a Prognostic Marker in Pulmonary HypertensionCHESTVol. 130Issue 5PreviewIn an article recently published in CHEST (May 2006), Fijalkowska et al1 provided important information on the value of N-terminal pro-type B natriuretic peptide (NT-proBNP) as a prognostic marker in patients with pulmonary hypertension (PH). There is growing interest in the role of natriuretic peptides in understanding the natural history of PH.2,3 The authors demonstrated that NT-proBNP is correlated with echocardiographic variables of right ventricular function and confirmed previous findings about the correlation of NT-proBNP with invasive hemodynamic variables. Full-Text PDF