Clinical condition and comorbidity as determinants for blood culture positivity in patients with skin and soft-tissue infections

The utility of performing blood cultures in patients with a suspected skin infection is debated. We investigated the association between blood culture positivity rates and patients' clinical condition, including acute disease severity and comorbidity. We performed a retrospective study, including patients with cellulitis and wound infection who had been enrolled in three Dutch multicenter studies between 2011 and 2015. Patients' acute clinical condition was assessed using the Modified Early Warning Score (MEWS; severe: MEWS >= 2) and comorbidity with the Charlson Comorbidity Index (CCI; severe: CCI >= 2). A total of 334 patients with a suspected skin infection were included. Blood cultures were performed in 175 patients (52%), 28 of whom (16%) had a positive blood culture. Data on the clinical condition were collected in 275 patients. Blood cultures were performed in 76% of the patients with a severe acute condition, compared with 48% with a non-severe acute condition (OR 3.5; 95% confidence interval: 2.0-6.2; p <0.001). Blood cultures were positive in 18% and 12% respectively (OR 1.7 (0.7-4.1); p = 0.3). Blood cultures were performed in 53% of patients with severe comorbidity, compared with 61% without severe comorbidity (OR 0.7; 0.4-1.2; p = 0.2). Blood cultures were positive in 25% and 10% respectively (OR = 3.1; 1.2-7.5; p = 0.02). The blood culture positivity rate among hospitalized patients diagnosed with skin infections was higher than the rates reported by the Infectious Diseases Society of America guidelines, particularly in patients with severe comorbidity. Therefore, the recommendations concerning blood culture performance in patients with a skin infection should be reconsidered