Normal White Blood Cell Count Does Not Rule Out Bacteremia
Journal Watch © 2012 Massachusetts Medical Society
Abstract and Introduction
Abstract
Of 289 patients with bacteremia, 52% had normal WBC count and 17% had neither WBC elevation nor fever.
Introduction
Despite multiple studies showing that a normal white blood cell (WBC) count does not exclude serious disease, physicians in all specialties continue to behave as if it did. To assess whether a normal WBC count or absence of fever reliably excludes bacteremia in patients with suspected infection, investigators conducted a secondary analysis of data from a prospective study of 3563 adults who had blood cultures at a single emergency department.
Among 289 patients (8%) with positive blood cultures, 77% had fever and 48% had elevated WBC count on initial measurement. Neither fever nor an elevated WBC count was noted in 17% of bacteremic patients.
Comment
The fact that leukocytosis is associated with infection does not mean that the white blood cell count is a good test for infection, because many patients with infection have no leukocytosis, and many patients with leukocytosis have no infection. Temperature is also not foolproof, but this investigation was limited by its reliance on initial temperature only, and some patients may have been found to be febrile later in the visit. The WBC count is the right test for neutropenia and malignancies of the white blood cell, but it is not a discriminatory test for infection. When evaluating a patient for possible infection, WBC counts should be used only as part of validated multivariable decision rules that have adequate predictive value for medical decision making, such as the Bacterial Meningitis Score (JW Pediatr Adolesc Med Jan 31 2007).
References
Seigel TA et al. Inadequacy of temperature and white blood cell count in predicting bacteremia in patients with suspected infection. J Emerg Med 2012 Mar; 42:254.
Journal Watch © 2012 Massachusetts Medical Society
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