Frequency and yield of blood cultures for observation patients with skin and soft tissue infections.

Objectives: 1) To measure frequency and yield of blood cultures obtained for observation status adult patients with skin and soft tissue infection (SSTI), 2) describe how often blood cultures were performed according to Infectious Diseases Society of America (IDSA) SSTI guideline indications, 3) identify proportion of patients meeting Center for Medicare Services (CMS) sepsis criteria.

Design: Retrospective cohort.

Setting: Tertiary academic center.

Patients: Consecutive adult observation status patients hospitalized with SSTI between July 2017 and July 2018.

Methods: We measured the proportion and results of blood cultures obtained among the study cohort and proportion of obtained cultures that satisfied IDSA indications.

Results: We identified 132 observation status patients with SSTI during the study period; 67 (50.8%) had blood cultures drawn. Only 14 (10.6%) patients met IDSA indications for culture; 51 (38.%) met Center for Medicare Services definition for sepsis. We identified two (3.0%) cases of bacteremia and two (3.0%) cases of skin bacteria contamination. In multivariable analysis, only temperature > 38 °C (OR 3.84, 95%CI 1.09-13.60) and white race (OR 2.71, 95%CI 1.21-6.20) were associated with blood culture obtainment; neither meeting IDSA SSTI guideline indications nor meeting CMS sepsis criteria was associated with culture.

Conclusions: Among observation status patients with SSTI, over half had blood cultures drawn, though 10% satisfied guideline indications for culture. The proportion of cultures with bacterial growth was low and yielded as many skin contaminants as cases of bacteremia. Our study highlights the need for further quality improvement efforts to reduce unnecessary blood cultures in routine SSTI cases.