Immunoradiometric Assay of Circulating C-Reactive Protein: Age-related Values in the Adult General Population

Abstract Background: Increased values of C-reactive protein (CRP), the classical acute phase protein, within the range below 5 mg/L, previously considered to be within the reference interval, are strongly associated with increased risk of atherothrombotic events, and are clinically significant in osteoarthritis and neonatal infection. Methods: A robust new polyclonal-monoclonal solid- phase IRMA for CRP was developed, with a range of 0.05–10.0 mg/L. Results: Plasma CRP values in general adult populations from Augsburg, Germany (2291 males and 2203 females; ages, 25–74 years) and Glasgow, Scotland (604 males and 650 females; ages, 25–64 years) were very similar. The median CRP approximately doubled with age, from ∼1 mg/L in the youngest decade to ∼2 mg/L in the oldest, and tended to be higher in females. Conclusion: This extensive data set, the largest such study of CRP, provides valuable reference information for future clinical and epidemiological investigations.