High Procalcitonin, CRP Predict Severe Bacteremia in Infants

Elevated procalcitonin and C-reactive protein are highly predictive of a severe bacterial infection in infants and young children admitted to the emergency department with fever without a source, investigators reported.

With their optimal cutoff points, procalcitonin (PCT) and C-reactive protein (CRP) had both better sensitivity and specificity for severe bacterial infections than either white blood cell or absolute neutrophil count, said Dr. Barbara Andreola of the University of Padova, Italy, and her coinvestigators. CRP has long been studied as a sensitive marker of bacterial infection, and there has been mounting interest in PCT. The aim of this study was to investigate their diagnostic use, compared with the current markers being used.

The prospective observational study included 404 infants and children younger than 3 years who were admitted to an emergency department with fever of unknown origin. The patients' median age was 10 months; 107 were infants younger than 3 months. Duration of fever was less than 24 hours in 143 children and less than 8 hours in 45 children (Ped. Infect. Dis. J. 2007;26:672–77).

A final diagnosis of severe bacterial infection (SBI) was made in 94 patients (23%); among those without SBI, 16% had focal bacterial infections, 9% had proven viral infections; and the rest of the patients had probable viral infections.

Blood work included tests for PCT and CRP levels, as well as white blood cell and absolute neutrophil counts. In a multivariate regression analysis, PCT and CRP were significantly better predictors of severe bacterial infection than cell counts or clinical assessment. An elevated white blood count was associated with twice the risk for SBI, while an elevated neutrophil count was associated with an increased SBI risk of 38%.

At a cut-off of 1 ng/mL, PCT was associated with a 6-fold increase in the risk of a severe bacterial infection, while a level of more than 2 ng/ml was associated with a more than 13-fold increased risk.

A CRP of more than 40 mg/L was associated with a fourfold increase in the risk of SBI, while a level of more than 80 mg/L was associated with more than an eightfold increased risk.

PCT also predicted specific organ involvement, Dr. Andreola and her associates said, with the highest values found in sepsis and meningitis. In children with fever of less than 8 hours' duration, PCT was the best predictor of SBI. “PCT seems to be a more accurate predictor at the beginning of an infection whereas CRP, if correctly employed by taking into account the time needed for its rise in the bloodstream, may be a better screening test in emergency settings, because of its overall better sensitivity and feasibility—its lower cost, better availability, and better historical practice,” they said.