title: High sensitivity C-reactive protein (Hs-CRP) remains highly stable in long-term archived human serum.
abstract: 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 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.
  
  
  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 7-11years of storage at -80°C [Hs-CRP (LT)].
  
  
  RESULTS
  Hs-CRP did not significantly change up to 11years 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 11years 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.
authors.affiliation: Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA. Electronic address: doumateya@mail.nih.gov.
authors.forename: Ayo P
authors.initials: AP
authors.lastname: Doumatey
authors.affiliation: Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Adebowale
authors.initials: A
authors.lastname: Adeyemo
authors.affiliation: Center for Research on Genomics and Global Health, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Charles
authors.initials: C
authors.lastname: Rotimi
mesh_terms: D015415:Biomarkers / Q000097:blood; D002097:C-Reactive Protein / Q000032:analysis*; D015925:Cryopreservation; D006801:Humans; D055550:Protein Stability; D015203:Reproducibility of Results; D013048:Specimen Handling / Q000592:standards; D013997:Time Factors
chemical_list: D015415:Biomarkers; D002097:C-Reactive Protein
keywords: Archived samples; Biomedical research; C-reactive protein; Long-term storage; Stability