Predictors of occult bacteremia in young febrile children in the era of heptavalent pneumococcal conjugated vaccine.

BACKGROUND Changes in the prevalence of pneumococcal occult bacteremia (PnOB) because of pneumococcal conjugated vaccine (PCV-7) may have altered the predictive value of the complete blood count (CBC) for selected patients at risk of having occult bacteremia (OB). OBJECTIVE To analyze the rate of OB in infants with high fever without source related to pneumococcal vaccination status and to study the yield of the CBC to identify children with OB in the era of PCV-7. METHODS Retrospective review of 1586 children of age 3-36 months admitted to a Pediatric Emergency Department with a CBC and a blood culture performed as part of their evaluation for fever. Patients with altered urinalysis were excluded. RESULTS Blood culture was positive in 15 (0.9%; pneumococcus 10, 0.6%). Of the 1586 children, 1040 (65.6%) showed less than 15,000 leukocytes/mm3 (2 PnOB, 0.19%). Of the 546 children with more than 15,000 leukocytes/mm3, eight had a PnOB (positive predictive value =1.46%, negative predictive value= 99.8%). Of the 1586 children, 1177 (74.2%) showed absolute neutrophil count less than 10,000/mm3 (3 PnOB, 0.25%). Of those 409 with more than 10,000 neutrophil/mm3, seven had a PnOB (positive predictive value= 1.71%, negative predictive value= 99.7%). Among the 429 children with at least two doses of PCV-7, one (0.23%) had a PnOB (vs. nine of 1090 - 0.82% - with no dose or one dose of PCV-7). CONCLUSION In the era of PCV-7, rate of PnOB is related to the pneumococcal vaccination status. The yield of the CBC is lower than in the prevaccinal era. Decisions based on CBC must be reconsidered.