stability of B-type natriuretic peptide (BNP) in plasma stored under different conditions when measured with the Lumipulse assay.

Natriuretic peptides are a laboratory tool with significant implications for the diagnosis and prognosis of heart failure (HF). The International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) recommended that assays must be examined for sample stability because there appears to be assay dependent. We aimed to evaluate the stability of B-type natriuretic peptide (BNP) under different handling conditions and using a BNP assay from Fujirebio Diagnostics (Tokyo, Japan). BNP concentrations were measured in plasma EDTA samples from 11 subjects to evaluate the stability at room temperature and at 4 °C and in 10 subjects to check the stability of samples stored at -20 °C during 1 and 3 months. Stability limit was defined according to Spanish Society of Laboratory Medicine (SEQC-ML) recommendations. At room temperature and 4 °C, BNP concentrations decreased progressively in samples collected in both groups, remaining stable within four hours from collection. BNP concentrations also were stable within four hours from collection in whole blood at room temperature. Finally, at -20 °C, BNP concentrations remained stable in both groups at 1 and 3 months, respectively. According to our results, BNP, stored at room temperature or at 4 °C, should be assayed in the first four hours after collection. Besides, BNP was shown to be stable in whole blood for at least four hours at room temperature. If the testing cannot be performed within the first four hours, the plasma should be frozen and kept at -20 °C for up to 3 months.