Should complete blood count be part of the evaluation of febrile infants aged ≤2 months?

Objective: To determine the utility and importance of total white blood cell count (WBC) and absolute neutrophil count (ANC) as markers of serious bacterial infection (SBI) in hospitalized febrile infants aged ≤2 months. Patients and methods: Data on WBC and ANC were collected prospectively for all infants aged ≤2 months who were hospitalized for fever at our centre. The patients were divided into two groups by the presence or absence of SBI. Results: A total of 1257 infants met the inclusion criteria, of whom 134 (10.7%) had a SBI. The area under the ROC curve was 0.73 (95% CI: 0.67-0.78) for ANC, 0.70 (95% CI: 0.65-0.76) for %ANC and 0.69 (95% CI: 0.61-0.73) for WBC. The independent contribution of these three tests in reducing the number of missed cases of SBI was significant. Conclusion: Complete blood cell count should remain as part of the routine laboratory assessment in this age group as it is reducing the number of missing infants with SBI. Of the three parameters, ANC and %ANC serve as better diagnostic markers of SBI than total WBC. However, more accurate tests such as C-reactive protein and procalcitonin should also be part of the evaluation of febrile infants in these age group as they perform better than WBC or ANC for predicting SBI.