Calorimetry faster than standard cultures to diagnosis fracture-related infection
Sensitivity, specificity, negative predictive value and positive predictive value for infection were better for isothermal microcalorimetry in patients with operated fractures than conventional cultures, a presenter said.
“Calorimetry for the detection of fracture-related infection – it significantly improved the detection by at least 2 days. This is obviously important for antibiotic stewardship, trying to get patients off broad-spectrum antibiotics to more narrowed down antibiotics, and also for getting patients out of the hospital a little faster,” Kyle H. Cichos, BS, of the University of Alabama, said at the Musculoskeletal Infection Society Annual Meeting.
Cichos and colleagues prospectively used both an isothermal calorimetry (ICM) system (Symcel) and standard tissue cultures to test and analyze tissue samples taken intraoperatively from 90 patients with a variety of fractures and fixation hardware between July 2020 and May 2021. ICM technology determines thermodynamic parameters of interactions of in a solution.
Researchers defined a sample with a change of 10 µW tested by calorimetry as being positive for infection.
In all, 66 patients in the study were infected based on the criteria for fracture-related infection (FRI), which was established at the Second International Consensus Meeting on Musculoskeletal Infection in 2018. Patient demographics were similar.
“The serologies that were obtained were elevated in infected cases, as expected,” Cichos said.
Researchers found the concordance between standard cultures and IMC was 88%. The sensitivity, specificity, negative predictive value and positive predictive value for IMC was 87%, 100%, 86% and 100%, respectively, compared with 80%, 94%, 79% and 97%, respectively, for standard cultures to detect FRI. For positive samples studied, the average time to diagnosis was about 48 hours for the standard cultures and about 6 hours for IMC.
“For patients on chronic antibiotics, we had 31 total patients. The average duration of antibiotics was 74.5 days,” Cichos said. “In these patients, the calorimetry showed markedly improved sensitivity and negative predictive value compared to cultures. The time to detection was, again, roughly ten-fold faster than the cultures.”