Limitations of C-reactive protein in diagnosis of neonatal infection caused by coagulase-negative staphylococcus

Abstract

Objective:

The objective of this study was to evaluate the utility of serial serum C-reactive protein (CRP) levels for detection of neonatal infection caused by coagulase-negative staphylococcus.

Setting:

A regional intensive care nursery.

Study

Design:All neonates with positive blood cultures for coagulase-negative staphylococcus were retrospectively evaluated to assess CRP levels and correlation with diagnosis of sepsis and length of therapy. Infants were categorized as having proven sepsis (on the basis of bacteria isolated from blood, or through signs and symptoms) or no sepsis (when findings are not consistent with sepsis), without consideration of CRP levels. CRP levels were recorded before the positive culture, on the day of the positive culture and 48 h to a week following initiation of therapy. Investigators were not blinded to clinical outcomes or CRP levels. Sensitivity, specificity and predictive values were calculated.

Result:

A total of 192 episodes of positive blood cultures for coagulase-negative staphylococcus were identified in 182 neonates. The peak CRP level had sensitivities of 85% and positive predictive value of 97% for suspected sepsis. Serial normal CRP levels were associated with a markedly reduced likelihood of infection. However, 24 (14%) infected neonates failed to mount a response depicting clear evidence of infection, demonstrating limited utility for CRP. Approximately, 80% of these neonates were male and had a mean birth weight of 840 g and a mean gestational age of 28 weeks. The infection occurred most commonly at a postnatal age of 2 to 3 weeks. There were no significant differences in race or ethnicity.

Conclusion:

Serial CRP levels are useful in the diagnostic evaluation of neonates with suspected infection. The lack of a positive response on the CRP value has good negative predictive value, except in those babies with a birth weight <1000 g during the first 2 to 3 weeks of life or with critical illness, where diagnostic performance may not be reliable. As found by other investigators, the sensitivity of a normal CRP at the initial evaluation is not sufficient to justify withholding antibiotic therapy.