BACKGROUND

The biochemical determination of cardiac natriuretic peptides, primarily brain natriuretic peptide (BNP) and the amino-terminal fragment of its pro-hormone proBNP (NT-proBNP), are reliable tools for diagnosing cardiac disease, establishing prognosis and evaluating the effectiveness of treatment. These biomarkers have proven to be of particular value in the management of chronic and acute heart failure patients, and in the outpatient and the emergency setting.

METHODS

A multicenter evaluation was performed to assess the practicability, and the analytical and clinical performance of a new point-of-care testing (POCT) PATHFAST NT-proBNP assay. This is an immunochemiluminescent assay using two polyclonal antibodies in a sandwich test format, and performed with a PATHFAST automated analyzer.

RESULTS

The limit of detection (mean+3 SD of the signal of 20 replicates of the zero calibrator obtained in one run) was 0.535 ng/L. An imprecision study, performed in accordance with the CLSI protocol, showed coefficients of variation of 4.0%-6.4% (within-run imprecision), 0.0%-3.4% (between-run imprecision), 5.5%-7.2% (between-day imprecision), 7.6%-8.9% (total imprecision). The method was linear to 28,755 ng/L. Slopes and intercepts ranged from 0.89 to 0.90 and from 10.96 to 22.85, respectively when lithium-heparin plasma samples (n=100) were used to compare the assay under evaluation with the routine laboratory methods (Dimension RxL, Stratus CS). When testing matched samples (n=52), a significant difference was found between the 50th percentile NT-proBNP concentration in K(2)EDTA whole blood, K(2)EDTA plasma, lithium-heparin plasma and serum. No significant interference was observed for NT-proBNP in lipemic (tryglicerides up to 28.54 mmol/L), icteric (total and conjugated bilirubin up to 513 and 13 micromol/L, respectively) or hemolyzed (hemoglobin up to 13.50 g/L) samples. The NT-proBNP concentration in a group of 180 healthy donors was significantly influenced by age and gender. In a selected population of patients (n=56) with acute dyspnea admitted to the emergency department, a marked reduction in cardiac natriuretic peptide concentrations was observed in hospitalized patients suffering from heart failure who had a better prognosis compared with those with a poorer prognosis (NT-proBNP mean Delta change, % from -22 to -71 vs. +9 to -11).

CONCLUSIONS

The satisfactory analytical and clinical performance of the PATHFAST NT-proBNP assay, together with its excellent practicability, suggests that it would be a reliable tool in clinical practice, in the emergency setting for point-of-care testing, as well as in the central laboratory.