The Reply

Abstract

We wish to thank Nagarajan for his interest in our study and for his thoughtful comments. We fully agree with most of them. Nagarajan argues that the increase in diagnostic accuracy achieved by using N-terminal pro-B-type natriuretic peptide (NT-proBNP) in addition to cardiac troponin T (cTnT), although statistically significant, may be of uncertain clinical value. Nevertheless, from a more pathophysiological point of view, we were puzzled by the fact that NT-proBNP but not B-type natriuretic peptide (BNP) was able to improve the diagnostic accuracy of cTnT.1Haaf P. Balmelli C. Reichlin T. et al.N-terminal pro B-type natriuretic peptide in the early evaluation of suspected acute myocardial infarction.Am J Med. 2011; 124: 731-739Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar Shifts of natriuretic peptides are known in patients with heart failure.2Hall C. Essential biochemistry and physiology of (NT-pro)BNP.Eur J Heart Fail. 2004; 6: 257-260Crossref PubMed Scopus (397) Google Scholar Further research is necessary to study shifts of BNP and NT-proBNP in patients with acute myocardial infarction to identify the pathophysiological reasoning behind this interesting phenomenon. Since publication of this study, more sensitive assays of cTnT, with even high early diagnostic accuracy,3Reichlin T. Hochholzer W. Bassetti S. et al.Early diagnosis of myocardial infarction with sensitive cardiac troponin assays.N Engl J Med. 2009; 361: 858-867Crossref PubMed Scopus (1327) Google Scholar, 4Keller T. Zeller T. Peetz D. et al.Sensitive troponin I assay in early diagnosis of acute myocardial infarction.N Engl J Med. 2009; 361: 868-877Crossref PubMed Scopus (921) Google Scholar have been gradually implemented in clinical practice in many countries. We would like to add that in this study of 658 patients, values for high-sensitive cardiac troponin T (hs-cTnT) were available in 637 (97%). NT-proBNP used in conjunction with hs-cTnT could not improve the diagnostic accuracy of hs-cTnT alone (area under the curve in each case was 0.96). Therefore, we fully agree with Nagarajan that, particularly after the implementation of more sensitive troponin assays, there seems to be very limited diagnostic use of NT-proBNP for acute myocardial infarction.Regarding the use of NT-proBNP in the early risk stratification of patients with suspected acute myocardial infarction, the simplicity of its clinical use may give NT-proBNP a relevant advantage over often bothersome scores.Chest pain patients presenting to the emergency department constitute a very heterogeneous group. Excluding myocardial infarction is more straightforward than singling out those patients who are at risk of death in the short and medium term. Several risk scores, such as the TIMI risk score or the GRACE score, have been established for that use. However, their calculation often is hindered due to missing information and room for interpretation concerning the components of their calculation (eg, unknown family history, significance of ST changes). Besides, these scores have not been developed for the heterogeneous group of acute chest pain patients. Determination of a single biomarker for risk assessment of acute chest pain patients is very attractive because it is readily available as a simple, rapid, inexpensive test in the emergency department. We fully agree with Nagarajan that the magnitude of the added value of NT-proBNP may differ from score to score as well as from cohort to cohort. We wish to thank Nagarajan for his interest in our study and for his thoughtful comments. We fully agree with most of them. Nagarajan argues that the increase in diagnostic accuracy achieved by using N-terminal pro-B-type natriuretic peptide (NT-proBNP) in addition to cardiac troponin T (cTnT), although statistically significant, may be of uncertain clinical value. Nevertheless, from a more pathophysiological point of view, we were puzzled by the fact that NT-proBNP but not B-type natriuretic peptide (BNP) was able to improve the diagnostic accuracy of cTnT.1Haaf P. Balmelli C. Reichlin T. et al.N-terminal pro B-type natriuretic peptide in the early evaluation of suspected acute myocardial infarction.Am J Med. 2011; 124: 731-739Abstract Full Text Full Text PDF PubMed Scopus (32) Google Scholar Shifts of natriuretic peptides are known in patients with heart failure.2Hall C. Essential biochemistry and physiology of (NT-pro)BNP.Eur J Heart Fail. 2004; 6: 257-260Crossref PubMed Scopus (397) Google Scholar Further research is necessary to study shifts of BNP and NT-proBNP in patients with acute myocardial infarction to identify the pathophysiological reasoning behind this interesting phenomenon. Since publication of this study, more sensitive assays of cTnT, with even high early diagnostic accuracy,3Reichlin T. Hochholzer W. Bassetti S. et al.Early diagnosis of myocardial infarction with sensitive cardiac troponin assays.N Engl J Med. 2009; 361: 858-867Crossref PubMed Scopus (1327) Google Scholar, 4Keller T. Zeller T. Peetz D. et al.Sensitive troponin I assay in early diagnosis of acute myocardial infarction.N Engl J Med. 2009; 361: 868-877Crossref PubMed Scopus (921) Google Scholar have been gradually implemented in clinical practice in many countries. We would like to add that in this study of 658 patients, values for high-sensitive cardiac troponin T (hs-cTnT) were available in 637 (97%). NT-proBNP used in conjunction with hs-cTnT could not improve the diagnostic accuracy of hs-cTnT alone (area under the curve in each case was 0.96). Therefore, we fully agree with Nagarajan that, particularly after the implementation of more sensitive troponin assays, there seems to be very limited diagnostic use of NT-proBNP for acute myocardial infarction. Regarding the use of NT-proBNP in the early risk stratification of patients with suspected acute myocardial infarction, the simplicity of its clinical use may give NT-proBNP a relevant advantage over often bothersome scores. Chest pain patients presenting to the emergency department constitute a very heterogeneous group. Excluding myocardial infarction is more straightforward than singling out those patients who are at risk of death in the short and medium term. Several risk scores, such as the TIMI risk score or the GRACE score, have been established for that use. However, their calculation often is hindered due to missing information and room for interpretation concerning the components of their calculation (eg, unknown family history, significance of ST changes). Besides, these scores have not been developed for the heterogeneous group of acute chest pain patients. Determination of a single biomarker for risk assessment of acute chest pain patients is very attractive because it is readily available as a simple, rapid, inexpensive test in the emergency department. We fully agree with Nagarajan that the magnitude of the added value of NT-proBNP may differ from score to score as well as from cohort to cohort. NT-proBNP in Acute Coronary Syndrome: Is It Really There Yet?The American Journal of MedicineVol. 125Issue 4PreviewI read the article by Haaf et al1 with great interest. This study reaffirmed the prognostic use of N-terminal pro B-type natriuretic peptide (NT-proBNP) in patients with acute coronary syndrome. It also claimed that NT-proBNP improves the diagnosis of acute myocardial infarction. In this study, the area under the curve was 0.79, 0.89, and 0.91 for NT-proBNP, cardiac troponin T, and both together, respectively. Although there was statistical significance (P=.033), the difference was probably not enough to implement routine use of NT-proBNP in diagnosis of myocardial infarction. Full-Text PDF