Practice and clinical factors associated with appropriateness of CT use in extremity soft tissue infection

Purpose: Soft tissue infections are common concerns. Although typically clinical diagnoses, imaging such as CT may be used to help increase diagnostic certainty or to evaluate the extent of infection. As extremities provide optimal opportunity for examination and diagnosis, CT appropriateness in this cohort is an area of interest for quality and safety. This study aims to describe adherence to ACR Appropriateness Criteria among patients with extremity cellulitis undergoing CT, and explore practice and clinical factors associated with Criteria nonadherence.

Methods/Materials: A retrospective review at a single academic medical center was conducted. Eligibility criteria included encounters between 2016-2021 involving patients with a clinical diagnosis of extremity cellulitis that received a CT scan. Exclusion criteria included postoperative evaluations, extremity implants excepting arthroplasty, trauma, and known deep infection or malignancy. Logistic regression was used to analyze factors influencing Criteria adherence.

Results: 323 patient encounters were eligible. Average age was 58±19, average BMI was 37±17 kg/m2, and 57% were male. The odds of meeting criteria for “Usually Not Appropriate” were 0.85 less in the inpatient setting compared to the ED (95% CI 0.75-0.95 p=0.001). Patient age, BMI, vital signs, and leukocytosis were not associated with significantly different odds of appropriateness. Overall, 56% encounters met criteria for “Usually Not Appropriate.” In 45% of encounters, patients did not receive radiography prior to CT. When radiography was performed first, 36% of cases did not have radiographic findings of swelling or gas.

Conclusions: In this study, we investigated CT use in patients with cellulitis of the extremities. The majority of patients did not receive “Usually Appropriate” utilization of CT. In most cases, radiography was not obtained prior to CT, highlighting an area for quality improvement. Inappropriate imaging was not associated with vital sign aberrations, age, or BMI, suggesting that other factors may influence CT ordering in this context, such as clinician preference. Our findings indicate the need for education specific to the emergency setting to increase imaging appropriateness.