C-Reactive Protein Kinetics in Newborns: Application of a High-Sensitivity Analytic Method in Its Determination

Abstract

C-Reactive protein (CRP) is a well-known indicator of inflammation. Advances in laboratory technology have enabled its quantification at lower concentrations by an automated analyzer (1)(2)(3). Because an increase in serum CRP concentration, even within the reference intervals of conventional analytic methods, has been related to increases in the risk of atherothrombotic events (4)(5)(6)(7), efforts for CRP quantification are currently directed toward healthy, elderly individuals or populations at risk of atherosclerotic diseases. When measured with a high-sensitivity analytic method, CRP may have diagnostic value in neonatal infection because newborns are unable to produce sufficient amounts of acute-phase proteins (8) and respond to infection with a smaller increase in CRP compared with that in adults (9). The utility of CRP for the diagnosis of neonatal infection has been the subject of lengthy controversy because of its unsatisfactory sensitivity for early-onset neonatal infection (10)(11)(13). The CRP concentration increases physiologically in newborns within the first few days after birth (9)(13). This increment seems to be related to the low diagnostic accuracy of CRP measurements in neonatal infection, particularly when measured shortly after birth. Similarly, other indicators of inflammation, such as procalcitonin and interleukin-6, demonstrate increases in noninfected babies within a few days after birth (14)(15)(16). In addition, very low CRP concentrations are found in the cord blood and sera of neonates in the immediate postnatal period (17). Therefore, the postnatal physiologic changes in CRP remain poorly understood. In this context, elucidation of serum CRP kinetics and an understanding of the mechanism(s) that cause its increase in the immediate postnatal period in noninfected babies would improve its diagnostic accuracy for early-onset neonatal infection. Using a high-sensitivity analytic method, we analyzed the serial changes in …