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Influence of sample matrix and storage on BNP measurement on the Bayer Advia Centaur
Giuseppe Lippi1, Antonio Fortunato, Gian Luca Salvagno
1Sezione di Chimica Clinica, Dipartimento di Scienze Morfologico Biomediche, Università degli Studi di Verona, Verona, Italy. ulippi@tin.it giuseppe.lippi@univr.it
Insights
For accurate congestive heart failure assessment, K2 EDTA plasma is the best sample for B-type natriuretic peptide (BNP) testing. Serum and heparin plasma show significant underestimation and misclassification, impacting clinical decisions.
Area of Science:
- Clinical Biochemistry
- Cardiology
- Laboratory Medicine
Background:
- Congestive heart failure (CHF) management relies on B-type natriuretic peptide (BNP) measurements.
- Preanalytical factors significantly influence the reliability of BNP testing.
- Controversy exists regarding sample matrix and storage effects on BNP stability.
Purpose of the Study:
- To compare BNP measurements across different sample matrices (serum, K2 EDTA plasma, heparin plasma).
- To evaluate the impact of storage conditions (-20°C and -80°C for 1 week) on BNP stability.
- To determine the optimal specimen type for reliable BNP testing.
Main Methods:
- BNP levels were measured using the Bayer Advia Centaur assay.
- Fresh samples of serum, K2 EDTA plasma, and heparin plasma were analyzed.
- Samples were also stored at -20°C and -80°C for one week before re-analysis.
Main Results:
- Heparin plasma and serum showed significant BNP underestimation compared to K2 EDTA plasma.
- Fresh serum and heparin plasma samples led to misclassification in 37% and 25% of cases, respectively, using a 100 ng/L cutoff.
- Storage at -20°C or -80°C had modest effects on K2 EDTA and heparin plasma but caused clinically significant increases in serum BNP levels.
Conclusions:
- K2 EDTA plasma is the most suitable matrix for both fresh and frozen BNP testing.
- Serum samples exhibit instability during storage, leading to clinically meaningful bias.
- Standardizing preanalytical procedures, particularly sample matrix selection, is crucial for accurate BNP assessment in CHF.
Abstract:
The assessment and management of congestive heart failure relies increasingly on the measurement of B-type natriuretic peptide (BNP). However, the effective contribution of this biochemical test in the clinical decision making is influenced by reliability of the measure, which also depends on several preanalytical issues. Since there is controversy on the influence of the matrix and the storage conditions on BNP measurement, we compared results of BNP in serum, K2 ethylene diamine tetra-acetic acid (EDTA) plasma and lithium heparin plasma fresh samples and in matching samples stored at -20 and -80 degrees C for 1 week. BNP measured on the Bayer Advia Centaur was systematically underestimated in heparin plasma (-47%) and serum (-62%) when compared to K2 EDTA plasma. According to the established 100 ng/L cutoff value, 25% and 37% of the fresh samples collected in heparin plasma or serum were misclassified from the reference K2 EDTA fresh specimen, respectively. When compared to the fresh specimens, the mean and interindividual bias observed for samples stored at either -20 degrees C or -80 degrees C was, overall, modest for K2 EDTA plasma (-2%) and heparin plasma (+6% and -4%, respectively), though it appeared clinically meaningful in serum (+47% and +28%, respectively). Although we can not rule out that other BNP assays using different antibodies may be not affected from degradation during storage to the same extent, results of our investigation demonstrate that K2 EDTA plasma is the most suitable specimens for BNP testing on fresh and frozen samples stored at either -20 degrees C or -80 degrees C for up to 1 week.
