The biopsy dilemma in spinal infections: timing of antibiotics and diagnostic yield.

PURPOSE: Establishing a microbiological diagnosis is critical in managing spinal infections, yet culture yields from biopsy are inconsistent and may be influenced by prior antibiotic therapy. This systematic review aimed to evaluate the impact of pre-biopsy antibiotic exposure on microbiological yield and to compare diagnostic performance across biopsy modalities. METHODS: Following PRISMA guidelines, five databases (Ovid MEDLINE, EMBASE, Web of Science, Cochrane Library, Scopus) were searched through June 2025. Eligible studies included adult and paediatric patients with suspected or confirmed spinal infection undergoing CT-guided, fluoroscopy-guided, or open biopsy. The primary outcome was microbiological yield (culture positivity) stratified by antibiotic exposure. Risk of bias was assessed using ROBINS-I. Pooled relative risks (RR) with 95% confidence intervals (CI) were calculated using fixed- or random-effects models. RESULTS: Thirty-eight studies involving over 2,000 patients were included. Nine comparative studies (n = 796) assessed the effect of antibiotics. Culture yield was significantly lower in antibiotic-exposed patients (39.2%) compared with unexposed (59.6%) (RR = 0.74, 95% CI: 0.63–0.86, p = 0.0001), with the greatest reduction observed within 72 h of initiation. Open biopsy demonstrated the highest yield (76.1%) compared with CT-guided biopsy (50.0%) (RR = 0.66, 95% CI: 0.57–0.76, p < 0.00001). No significant difference was found between CT-guided and fluoroscopy-guided techniques. Aggregate non-comparative yields were 44.1% for CT-guided, 37.0% for fluoroscopy-guided, and 84.2% for open biopsy. CONCLUSION: Prior antibiotic therapy reduces microbiological yield in spinal infection, particularly within the first 72 h. Open surgical biopsy provides superior diagnostic accuracy compared with percutaneous techniques, even in antibiotic-exposed patients. A biopsy-first strategy should be prioritised in stable patients, with early surgical consultation when empirical antibiotics cannot be delayed. These findings should be interpreted in the context of the predominantly retrospective evidence base and the inconsistent reporting of microbiological methods across studies. Standardised microbiological protocols and further prospective research are warranted to refine biopsy timing and technique.