Pilot randomised controlled trial of probe to bone diabetic foot ulcer therapy (PROBE-DFU trial) – Study protocol

BACKGROUND: The probe-to-bone (PTB) is a simple, bedside clinical test that can assist in diagnosis of diabetic foot osteomyelitis (OM). The utility of PTB varies depending on the population, with a lower positive predictive value in lower-risk outpatients. METHODS: This is a protocol for a pilot, feasibility and safety multi-centre randomized controlled trial. 80 patients, with PTB diabetic foot ulcers and without initial X-ray findings of OM, will be randomized to 2 weeks antibiotic therapy or 6 weeks of antibiotic therapy at a 1:1 ratio. The primary outcomes will be to assess feasibility (eligibility to recruitment ratio, retention rate, adherence to protocol and cross-over from intervention to control group) and safety (serious adverse events, antibiotic-associated adverse events, Clostridium difficile associated diarrhea and hospitalization) in this cohort. Exploratory clinical outcomes will include recommencement/continuation of antibiotic therapy or requirement for surgery, and the proportion of participants that demonstrate new radiological changes of OM on serial X-ray imaging. Follow-up will occur at 14 days, 42 days and 90 days post-recruitment. DISCUSSION: This is the first randomised trial assessing the feasibility and safety of shorter antibiotic therapies in patients with low-risk PTB diabetic foot ulcers. The findings of this trial will inform the design of future large multi-site randomised trials to risk stratify diabetic foot ulcers and better understand how to treat diabetic foot OM. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry (ANZCTR): 12624000266561. Registered on 15/03/2024.Registration URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=386823&isReview=true.