[Type B natriuretic peptide (BNP) versus n-terminal type B natriuretic propeptide in the diagnosis of cardiac failure in the elderly over 75 population]. / Peptide natriurétique de type B (BNP) versus n-terminal propeptide natriurétique de type B (NT-proBNP) pour le diagnostic de l'insuffisance cardiaque chez le sujet agé de plus de 75 ans.

Type B natriuretic peptide (BNP) versus n-terminal type B natriuretic propeptide in the diagnosis of cardiac failure in the elderly over 75 population The value of BNP is well established in the diagnosis of cardiac failure in cases of dyspnoea in the emergency room in young and, more and more, in elderly subjects. However, there are few studies comparing the diagnostic value of BNP and of the n-terminal pro-BNP in patients over 75 years of age. The aim of this study was to compare the diagnostic value of BNP and NT-pro BNP in dyspnoea of the elderly patient. One hundred and three consecutive patients over 75 years of age admitted to the emergency unit for dyspnoea were included. A blood sample for measuring the BNP (Biosite) and the NT-proBNP (Roche Diagnostic) was taken in the admission unit in addition to the standard blood workup. The final reference diagnosis was established by two independent cardiologists. Of the 103 patients, 61 were women and the average age was 84.9 +/- 6.2 years. The final diagnosis was cardiac failure in 49 patients (48%), pulmonary embolism in 6 patients, an acute exacerbation of chronic obstructive airways disease in 36 patients and an acute bronchitis in 30 patients. In 9 cases, the dyspnoea was considered to result from mixed cardiac and pulmonary disease. Renal function was assessed by calculating the creatinine clearance by Cockcroft and Gault's formula. The average value of the creatinine clearance was 41.7 +/- 16.4 ml/min indicating that mild renal failure was relatively common. The diagnostic value, assessed by the area under the ROC curve, was similar for the BNP (0.79; CI: 0.70-0.88) and NT-proBNP (0.80; CI: 0.71-0.89). A BNP value of 300 pg/ml had the same sensitivity and specificity as an NT-proBNP of less than 1 500 pg/ml. A BNP of less than 200 pg/ml and an NT-proBNP of less than 1 000 pg/ml had excellent negative predictive values for excluding the diagnosis of cardiac failure. The authors conclude that the BNP and NT-proBNP are useful for the diagnosis of cardiac failure in acute dyspnoea of the elderly and seem to have a comparable diagnostic value.

[Non-radioimmunometric NT-ProBNP and BNP assays: impact of diluent, age, gender, BMI]. / Corrélation BNP-NT-proBNP: rôle du diluant, influence de l'âge, du sexe et de l'indice de masse corporelle.

We examined the analytical correlation between non-radioimmunometric plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) and B-type natriuretic peptide (BNP) and evaluated whether NT-proBNP or BNP was influenced by age, gender and/or body mass index (BMI). Electro-chemiluminescence (Elecsys, Roche diagnostic) and a single use fluorescence (Triage, Biosite) immunoassays were used to measure NT-proBNP and BNP levels respectively. As a preliminary, seven different diluents usually used in immunoassays were tested and the "speciality diluent" (Ortho Clinical Diagnostic) was validated to increase the linearity of BNP immunoassay above 5000 pg/mL. Data were collected prospectively from patients admitted to the emergency department for acute dyspnea. Plasma BNP and NT-proBNP were measured at admission. Reference diagnosis was adjudicated by 2 independent cardiologists using the European Society of Cardiology guidelines. One hundred and sixty consecutive patients were included: 84 females and 76 males, mean age 80.1 +/- 13.5 (16-98). The analytical correlation between NT-proBNP and BNP was satisfactory using the equation: log10(NT-proBNP) = 1.1xlog10(BNP) + 0.57 and a correlation r = 0.93. This was established over a wide range of concentration (5-6400 pg/mL for BNP). Age and gender were known to influence circulating BNP levels. We showed that the correlation between BNP and NT-proBNP was not influenced by age, gender and body mass index of patients which suggests that the distribution of both peptides was similarly affected by these parameters. We conclude that NT-proBNP, as assayed in the present study, correlates closely with BNP. Used in conjunction with other clinical information, rapid measurement of BNP or NT-proBNP is useful in establishing or excluding the diagnosis of congestive heart failure in patients with acute dyspnea.