Importance of high sensitivity c-reactive protein (Hs-CRP)in stored samples of human serum

Background: The 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 card in vascular and/or inflammatory processes in clinical care and large epidemiologic studies. (Ayo et al., 2014) Therefore, assessing Hs-CRP stability in archived samples at a given temperature is important to insure precision of measurements over time and the validity of studies using archived samples. Methods: We 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)). Results: Hs-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. Conclusions: Long-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.