Early detection of bacteremia in an outpatient clinic

A total of 570 patients, aged less than 24 months, who were seen in the emergency room at Texas Children's Hospital for evaluation of acute febrile illness had a WBC count, differential count, and a blood culture obtained. Bacteremia occurred in 7.7% (n = 44) (22 Haemophilus influenzae; 17 Streptococcus pneumoniae; three Escherichia coli; one group B Streptococcus; one Staphylococcus aureus). The sensitivity, specificity, and positive predictive value of morphologic changes (vacuolization and toxic granulation) of polymorphonuclear neutrophils (segmented neutrophils plus band cells), WBC count greater than or equal to 15,000/microL and band cells greater than or equal to 500/microL were examined. Additionally, abnormalities in three of four tests (WBC count greater than or equal to 15,000/microL, band cells greater than or equal to 500/microL, segmented neutrophils greater than or equal to 10,000/microL, and/or total polymorphonuclear neutrophils greater than or equal to 10,500/microL) were evaluated. Morphologic changes of polymorphonuclear neutrophils were noted frequently in patients with culture-proven bacteremia (63% and 51% positive predictive value for vacuolization and toxic granulation, respectively) and were more predictive of bacterial infection than traditional tests. If both vacuolization and toxic granulation were present, the positive predictive value increased to 76%. Examination of the peripheral blood smear may provide important adjunctive information for the presence of bacteremia prior to bacteriologic confirmation.