Clinical Chemistry
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Clinical Chemistry 53: 1720-1721, 2007; 10.1373/clinchem.2007.092924
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(Clinical Chemistry. 2007;53:1720-1721.)
© 2007 American Association for Clinical Chemistry, Inc.

Letters to the Editor

The authors of the article cited above respond:

Aldo Clerico1,2,a, Marianna Fontana1, Luc Zyw1, Claudio Passino1,2 and Michele Emdin1

1 Consiglio Nazionale delle, Ricerche Institute of, Clinical Physiology, Cardiovascular Medicine Department and, Cardiovascular Endocrinology Laboratory, Pisa, Italy
2 Scuola Superiore S. Anna, Pisa, Italy

aAddress correspondence to this author at: Consiglio Nazionale delle Ricerche Institute of Clinical Physiology Via Trieste 41, 56126 Pisa, Italy. Fax 011-39-0585; e-mail clerico{at}cnr.it.


To the Editor:

We are grateful to Dr. Christian Mueller for his constructive suggestions regarding our review (1). Actually, area under the curve (AUC) values of brain natriuretic peptide (BNP) and the N-terminal part of the propeptide of BNP (NT-proBNP) (0.85 and 0.80, respectively) assays related to the study by Ray et al. (2) were erroneously inverted, whereas sensitivity and specificity were correctly indicated in Table 2 of our review (1). Nevertheless, we confirm that the conclusions of our review were correct; they were based on the diagnostic odds ratios, which were derived from sensitivity and specificity values.

As suggested by Dr. Mueller, we recalculated the pooled AUC values by using the random-effects model according to the DerSimonian-Laird method, and we report the Forest plots for BNP and NT-proBNP assays in Fig. 1 , A and B, respectively. Indeed, the calculated AUC values for NT-proBNP [0.8615 (0.8144–0.9007)] and BNP [0.8477 (0.7909–0.9045)] assays were very similar to those reported in our review (1), and statistical reappraisal confirmed that the AUCs are not significantly different between BNP and NT-proBNP assays for diagnosis of acute heart failure.


Figure 1
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  		Figure 1. Forest plots of AUC values for BNP (part A) and NT-proBNP (part B) reported by studies concerning patients with acute heart failure (see Table 2 of Ref. (1)1).

The black diamond with the dotted line indicates the pooled DOR with 95% CI.

With regards to Mueller’s challenge of our definition of "chronic heart failure" regarding the studies reported in Table 1 and Fig. 2 of our review (1), we note that all of these studies aimed to detect structural myocardial impairment leading to left ventricular systolic and/or diastolic dysfunction either in asymptomatic or symptomatic patients, that is, stage B or C of the definition of heart failure, according to the classification of the American Heart Association/American College of Cardiology task force for the diagnosis and management of chronic heart failure (3).

One important finding of our metaanalysis (1) is represented by the heterogeneity of data published on the comparison of diagnostic accuracies of BNP and NT-proBNP, especially for studies concerning chronic heart failure. Evidently, the large variability of these data may be decreased if statistical analyses are performed separately for specific clinical conditions (e.g., systolic or diastolic dysfunction), as suggested by Mueller. However, this approach may not be feasible at this time, considering the small number of studies comparing the diagnostic accuracies of BNP and NT-proBNP. In conclusion, further studies are needed to evaluate differences in diagnostic accuracy of BNP and NT-proBNP assay in patients with heart failure.


Acknowledgments

Grant/funding support: None declared.

Financial disclosures: None declared.


References

  1. Clerico A, Fontana M, Zyw L, Passino C, Emdin M. Comparison of the diagnostic accuracy of brain natriuretic peptide (BNP) and the N-terminal part of the propeptide of BNP immunoassays in chronic and acute heart failure: a systematic review. Clin Chem 2007;53:813-822.[Abstract/Free Full Text]
  2. Ray P, Arthaud M, Birolleau S, Isnard R, Lefort Y, Boddaert J, et al. Comparison of brain natriuretic peptide and probrain natriuretic peptide in the diagnosis of cardiogenic pulmonary edema in patients aged 65 and older. J Am Geriatr Soc 2005;53:643-648.[CrossRef][Web of Science][Medline] [Order article via Infotrieve]
  3. Hunt SA. American College of Cardiology; American Heart Association Task Force on Practice Guidelines (Writing Committee to Update the 2001 Guidelines for the Evaluation and Management of Heart Failure). ACC/AHA 2005 guideline update for the diagnosis and management of chronic heart failure in the adult: a report of the American College of Card Writing Committee to Update the 2001 Guidelines for the Evaluation and Management of Heart Failure. J Am Coll Cardiol 2005;46:e1-e82.[Free Full Text]




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