Outpatient Diabetic Foot Ulcer Diagnosis With Positive Wound Culture Linked to Subsequent Hospital Admission

Outpatient diagnosis of a diabetic foot ulcer with a positive wound culture is associated with subsequent hospital admission for systemic infection, according to research results published in Open Forum Infectious Diseases.

Researchers conducted an exploratory, retrospective study in order to evaluate the relationship between outpatient diagnosis of an index diabetic foot ulcer and any subsequent admissions for invasive bacterial infection including osteomyelitis, bacteremia, or endocarditis.

Data were collected from a Veterans Affairs health system database for outpatient visits between October 2015 and September 2018. The primary study outcome was incidence of hospital stay for invasive infection during the 1-year period after the index diagnosis.

The study cohort included 13,744 patients (median age, 69 years; 98% men; 65% hbA1c ≤9) across 104 facilities who were diagnosed with a new diabetic foot ulcer, 13.2% of whom had a foot wound culture collected during the 1-year follow-up period.

Within the patients who had a wound culture collected, 47.4% had at least 1 positive foot wound culture. The most positive organism found was S aureus (38.8%), followed by Enterococcus faecalis (17.3%).

During the study period, 19.4% of patients were hospitalized due to invasive infection, including acute osteomyelitis (n=174), bloodstream infection (n=157), and endocarditis (n=21). Positive foot wound culture was associated with higher odds of hospitalization for invasive infection (21.7% vs 17.2% in negative foot wound cultures).

Median time from index ulcer documentation to invasive infection admission was 80 days (interquartile range [IQR] 31-187). Within this group, 52.2% had positive blood cultures and 66.4% had a prior foot wound that grew the same organism.

Adjusted odds for hospitalization within 1 year for invasive systemic infection in those with a positive foot wound culture was 1.39 (95% CI, 1.09-1.77). Results of a multivariable analysis showed that patient demographic and historical factors were “not significantly associated with the outcome,” although some comorbidities, such as anemia and drug use, were predictive of invasive systemic infection.

Study limitations include a lack of generalizability outside of the VA system, missing hospitalization data if patients were admitted to private sector hospital facilities, and a lack of data on specific treatments and details about the ulcers.

“Diabetic foot ulcers with positive wound cultures diagnosed in the outpatient setting are associated with subsequent admission for invasive systemic infection,” the researchers concluded. “Variation in management strategy used within different facilities may impact clinical outcomes and is an important focus for future study to better inform management of this common, yet understudied, condition.”

Disclosure: One study author declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

Reference

Branch-Elliman W, Sturgeon D, Karchmer AW, Mull HJ. Association between diabetic foot infection wound culture positivity and 1-year admission for invasive infection: A multi-center cohort study. Open Forum Infect Dis. 2021; ofab172. doi: 10.1093/ofid/ofab172