Key result
Sodium-citrate plasma yields ~95% higher baseline CNP than EDTA, while NT-proCNP remains stable.
Why the study?
Reliable data on differences in CNP concentration between serum and plasma samples and the influence of delayed blood sample processing were lacking.
Observational (n=12)
No
Absolute Event Rate: 1.933% vs 0.991%
p-value: p=0.001
NT-proCNP is stable for at least two hours at room temperature and provides more consistent data across sample types than CNP, making it preferable for clinical applications.
NT-proCNP stability across sample types may favor its use over CNP; leaves open validation against clinical outcomes in patient cohorts.
BACKGROUND: C-type natriuretic peptide (CNP) has anti-inflammatory, anti-proliferative, and anti-migratory properties. During the past years, CNP has attained an increasing interest by many research groups, especially in the cardiovascular field. Nevertheless, still no reliable data exist on the difference of CNP concentration between serum and plasma samples. Also, the influence of delayed blood sample proceeding is unknown. The aim of this study was to investigate the difference of CNP and NT-proCNP concentrations between serum and plasma samples. In order to identify potential methodological bias, this study should also validate the stability of CNP and NT-proCNP in full blood samples stored at room temperature. FINDINGS: Triplets (serum, plasma, full blood) of fasting blood samples from 12 healthy male individuals were collected. Analysis of CNP and NT-proCNP concentration was performed immediately following sampling, and after 30 minutes or 2 hours of storage at room temperature. Mean serum concentrations at baseline were 0.997 ± 0.379 ng/ml for CNP and 58.5 ± 28.3 pg/ml for NT-proCNP. Furthermore, NT-proCNP concentration did not change significantly during the allotted time and did not differ between serum, plasma, and full blood samples. At baseline, concentrations of CNP were significantly different between samples containing either sodium-citrate or EDTA as a clotting inhibitor (1.933 ± 0.699 ng/ml vs. 0.991 ± 0.489 ng/ml, p = 0.001). CONCLUSIONS: CNP and NT-proCNP are stable for at least two hours, even when sample processing is delayed or blood probes are stored at room temperature. NT-proCNP assay demonstrated more consistent and reliable data and should therefore be preferred for usage in clinical applications. Nevertheless, as recommended for ANP and BNP, immunoassays for CNP should also be standardized or harmonized in the future.
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Kuehnl et al. (2013) conducted an observational in Healthy (n=12). Sodium-citrate plasma processing vs. EDTA full blood or serum processing was evaluated on CNP concentration at baseline (p=0.001). Plasma samples containing sodium-citrate yielded significantly higher baseline CNP concentrations compared to EDTA samples (1.933 vs. 0.991 ng/ml, p=0.001), while NT-proCNP remained stable across all sample types for up to 2 hours.
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