The complete blood count is a nonspecific test that may assist in the identification of bacteremia and SBI but is not diagnostic and must be interpreted in the clinical context. Although the incidence of bacteremia rises with white blood counts of 10,000/pL or more, there is no threshold value of the white blood count (WBC) that distinguishes between bacteremic and nonbacteremic patients or identifies patients with SBI with adequate sensitivity and specificity. A WBC of 5000/pL or less in ill-appearing infants is suggestive of overwhelming bacterial sepsis but in well-appearing infants suggests benign viral illness with transient bone marrow suppression. The choice of a threshold of WBC of 15,000/pL or more for obtaining a blood culture in the setting of a well-appearing child with temperature of 39°C or higher and no or minor focus of infection will identify only 65 percent of those with OB. Moreover, only 7.5 percent of such children who meet these clinical criteria will prove to be bacteremic. Decreasing the WBC threshold for obtaining a blood culture to improve sensitivity markedly decreases the specificity and predictive value of the test. 26 Other available screening tests, such as absolute band count, erythrocyte sedimentation rate, and C-reactive protein, have failed to provide significantly greater sensitivity or specificity. Although the blood culture is the "gold standard" for the identification of bacteremia, its result cannot be predicted by a screening test with any degree of confidence at the time of initial ED evaluation. The pursuit of OB should not distract emergency physicians from carefully evaluating febrile infants for focal serious bacterial infections, including UTI, pneumonia, meningitis, and soft tissue, bone, or joint infection.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.