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Most patients with acute bacterial cellulitis can be treated successfully without the diagnostic tests clinicians often feel obliged to order, including blood cultures and imaging of affected areas. Clinicians often reflexively order these tests nonetheless.
Boston researchers conducted a retrospective review of the utility of common tests in managing 183 patients at a single hospital whose cellulitis was severe enough to result in admission to an inpatient ward or extended observation unit. Blood cultures were obtained in 60 of 183 patients (33%), of whom only 18 were sick enough for sepsis to be suspected; in only 1 patient were the cultures positive. Imaging tests, including x-rays, ultrasonography, computed tomography, and magnetic resonance imaging, were obtained 124 patients (68%); imaging changed diagnoses and management in 8 (abscesses in 5, osteomyelitis in 2, and hematoma in 1). The researchers extrapolate from these numbers to estimate that, nationwide, the cost of unnecessary cultures and imaging tests in patients with cellulitis exceeds US$226 million annually.
Ko LN et al. Clinical usefulness of imaging and blood cultures in cellulitis evaluation. JAMA Intern Med 2018 Apr 2; [e-pub]. (http://dx.doi.org/10.1001/jamainternmed.2018.0625)
Comment
Almost all patients with cellulitis will get better with empirical antibiotics: Guidelines suggest that cultures and imaging be reserved for patients with severe immunocompromise or signs of sepsis. Other studies have argued for the value of point-of-care ultrasound to exclude small abscesses that are not obvious on physical examination (BMJ Open 2017; 7:e013688), but, in this study, even cellulitis patients who were sick enough to be hospitalized seldom benefitted from testing. One might argue that negative test results bring some peace of mind, but the attached price tag is gigantic.