Background Early diagnosis of bacterial infections in extremely low birth weight (ELBW) infants is difficult and these infections easily progress rapidly to become systemic, suggesting the need for an objective, sensitive indicator for early treatment. The evanescent wave immunoassay enables the most sensitive measurement of C-reactive protein (CRP) in only 50 μl of whole blood in 10 minutes. In this study, we measured CRP in ELBW infants up to 7 days old using the evanescent wave immunoassay, and compared their normative standards with those of term infants.

Subjects and Methods The subjects were 102 ELBW infants born in our neonatal intensive care unit between 1 January 2002 and 31 December 2007. Blood was collected daily between days 0 and 5 from the term infants, and between days 0 and 7 from the ELBW infants. CRP in ELBW infants was measured using EV20, and the 90 percentile values were compared with the normative standards of the term infants.

Results A transient, physiological increase in CRP was observed in the ELBW infants as in the normal newborns. However, the term infants and ELBW infants differed in the level and timing of the physiological increase in CRP: 3768.34 μg/dl on day 1 in the term infants and 637.5 μg/dl on day 2 in the ELBW infants.

Discussion We speculate that the difference in postnatal changes in CRP levels is due to a milder and slower response to delivery stress in ELBW than that in term infants. The results obtained are useful for the early detection of infections and avoidance of unnecessary antibiotic therapy in ELBW infants.