Blood Cultures for Cellulitis Often Needlessly Ordered

Despite existing recommendations, blood culture is overused in patients with suspected, uncomplicated cellulitis, according to a research letter published April 2 in JAMA Internal Medicine.

Cellulitis is a common bacterial skin infection affecting an estimated 14.5 million American annually. In 2014, the Infectious Disease Society of America released evidence-based guidelines against the use of blood cultures except in patients who were highly immunocompromised, exhibiting systemic toxic effects, or who had sustained animal bites. (The guidelines also advised against imaging in most cases.)

The researchers retrospectively reviewed the cases of 183 patients seen in Massachusetts General Hospital’s emergency department (October 2014 to February 2017) for suspected uncomplicated cellulitis and who were subsequently admitted to inpatient medicine or an observation unit. The clinical usefulness and cost of blood cultures (and imaging) was evaluated.

Despite the existing recommendations, nearly one-third of patients (32.8 percent) received blood cultures, but only 18 of the 60 blood cultures were appropriately ordered. Growth was detected in just one of these 60 cultures. The authors said that results from blood cultures “seldom” altered diagnosis or treatment.

Based on estimates of blood culture costs and imaging (which was ordered inappropriately in two-thirds of all patients), the yearly cellulitis hospitalization rate, and the rate at which imaging and blood cultures were ordered within this cohort, the authors estimated that approximately $226.9 million dollars is spent annually on these “largely clinically useless diagnostic studies.”

“Radiologic imaging and blood cultures have low clinical usefulness for evaluation and treatment of cellulitis,” write the authors led by Lauren Ko, from Harvard University in Boston. “In addition, they portend significant cost to the health care system.”

Takeaway: Blood cultures are commonly inappropriately ordered in the diagnostic workup of patients with suspected cellulitis.