Friday May 22, 2009 (pediatric pearl day)
What is the best inflammatory marker to diagnose nosocomial infection in children undergoing cardio-pulmonary bypass?

Scope of Problem: Neonates and infants who undergo surgery for congenital heart defects are at risk of nosocomial infections. However, these children undergoing cardiac surgery with cardiopulmonary bypass often develop a systemic inflammatory response syndrome with an increase in inflammatory markers which makes the diagnosis of infection in the postbypass patient difficult.

STUDY: In a prospective cohort study the investigators tested the hypothesis that procalcitonin (PCT) is a more reliable marker of infection than C-reactive protein (CRP) or and immature-to-total neutrophil ratio (ITR) in the post-CPB child.

The investigators found that, in a receiver operating characteristic curve analysis, PCT was the most reliable variable for the diagnosis of probable/definite sepsis with area under the curve 0.84 (95% confidence interval, 0.75–0.92) compared with 0.73 (0.62–0.84) for ITR and 0.62 (0.52–0.73) for CRP.

A serum PCT concentration more than 2.2 ng/mL was the best cut-off value for the diagnosis of sepsis, with 84% sensitivity and 72% specificity. This cut-off has a PPV of only 32%, which would mean that only about one in three children suspected and hence treated for sepsis would actually have true sepsis. The NPV is 97%, which would mean that 3 in 100 would potentially not be treated when they really did have sepsis. The best cut-off depends on the day after bypass. An increase in the marker is more likely to suggest infection than a single value, particularly in the first days postbypass.

Conclusions: CRP was a poor marker of sepsis in this study. Children with a PCT less than 2.2 ng/mL or ITR less than 0.08 were unlikely to have definite or probable sepsis. However, only a third of children with high values of PCT and ITR had definite or probable sepsis.



Reference: click for reference

Procalcitonin versus C-reactive protein and immature-to-total neutrophil ratio as markers of infection after cardiopulmonary bypass in children. - Pediatric Critical Care Medicine. 10(2):217-221, March 2009.