High sensitivity C-reactive protein (Hs-CRP) remains highly stable in long-term archived human serum

• We evaluate the expected stability of CRP in serum samples banked for several years.
• Long-term storage at -80°C has no apparent effect on CRP concentrations.
• The time elapsed between sample collection and CRP assay has no effect on CRP stability.
• These findings provide useful operational data for epidemiological studies and biobanks.

BackgroundThe stability of biomarkers in stored biomedical samples is crucial, especially when storage is for extended periods of time. High-sensitivity CRP (Hs-CRP) is a biomarker of low grade inflammation that is extensively used to identify and study cardiovascular and/or inflammatory processes in clinical care and large epidemiologic studies. Therefore, assessing Hs-CRP stability in archived samples at a given temperature is important to ensure precision of measurements over time and the validity of studies using archived samples.MethodsWe evaluated the stability of Hs-CRP in 30 randomly selected human serum samples by measuring Hs-CRP concentrations in freshly collected sample [Hs-CRP (0)] and in the same set of samples after 7–11 years of storage at − 80 °C [Hs-CRP (LT)].ResultsHs-CRP did not significantly change up to 11 years of storage at − 80 °C as shown by a negligible median difference between Hs-CRP (0) and Hs-CRP (LT), delta(Hs-CRP (0)–Hs-CRP (LT)) = − 0.01, p = 0.45. There was a good concordance and agreement between Hs-CRP (0) and Hs-CRP (LT) as measured respectively by Lin's coefficient of correlation (ρC = 0.98) and Bland–Altman analysis (mean difference = − 0.02, 95% CI [− 0.04–0.0045] p = 0.107). In addition, the data also suggest that the time elapsed between collection and Hs-CRP measurement does not affect Hs-CRP stability over time when samples are kept under the appropriate conditions.ConclusionsLong-term storage at − 80 °C for up to 11 years did not significantly affect the stability of serum Hs-CRP. Given the cost and time for collecting fresh samples, this observation represents an important finding for biomedical research and clinical care.