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Pleural fluid NT-pro-BNP levels better than BNP for confirming cardiac effusions

Reuters Health • The Doctor's Channel Daily Newscast

NEW YORK (Reuters Health) – For diagnosing heart failure-related pleural effusions, pleural fluid levels of N-terminal pro-brain natriuretic peptide (NT-pro-BNP) are more accurate than BNP levels, say researchers from Spain.

Dr. Jose M. Porcel and colleagues from Arnau de Vilanova University Hospital in Lleida used data from 90 patients with heart failure and 91 with noncardiac pleural effusions to investigate the utility of NT-pro-BNP, BNP, and ST2 (an IL-1 receptor family member) as pleural fluid biomarkers of heart failure.

According to results published in the September Chest, median pleural fluid concentrations of NT-pro-BNP and BNP were significantly higher in cardiac effusions than in noncardiac effusions. ST2 levels were considerably less discriminating.

Areas under the curve (AUC) were 0.96 with NT-pro-BNP, 0.90 with BNP, and 0.59 with ST2, the authors report.

“The best discriminating properties” were cutoff values of 1,300 pg/ml for NT-pro-BNP and 115 pg/ml for BNP, they add.

The BNP the reference level “was particularly accurate in men >75 years,” the investigators found. For women, however, cutoff values of 40 pg/ml and 80 pg/ml were more accurate in younger and older groups, respectively. Also, the reference cutoff value had lower sensitivity and specificity in younger men than in the men over 75 years.

The NT-pro-BNP cutoff remained useful regardless of age, sex, or serum creatinine level, however.

“Until more data are available on how these markers should be integrated into clinical care, their routine use in patients with an obvious diagnosis of heart failure is not warranted,” the authors write.

“Rather,” they add, “NT-pro-BNP measurements should be limited to cases in which the cause of the pleural effusion remains uncertain after the standard clinical assessment.”

In a related editorial, Dr. Richard W. Light from Vanderbilt University, Nashville, Tennessee describes this report as “important because it demonstrates that BNP measurements are a poor substitute for NT-pro-BNP measurements.”

Reference:
Chest 2000;136:671-677,656-658.