Retrospective review of CT‐guided intervertebral disc biopsies performed at a tertiary referral centre for suspected osteodiscitis

Introduction Patients with osteodiscitis are often prescribed antibiotics prior to biopsy. There is controversy in the literature about whether antibiotic pre‐treatment prior to CT‐guided biopsy decreases the microbiological culture yield. Conclusions from previous studies are influenced by sample size error and selection bias. Our study, conducted in a large number of patients over a 10‐year period, clarifies this issue so that best clinical practice is assured. Methods We performed a retrospective audit of the clinical, radiological and microbiological features of adult patients who underwent CT‐guided biopsies for suspected osteodiscitis at a tertiary institution. Patients who had received intravenous antibiotic therapy in the month prior to biopsy or oral antibiotics 2 weeks prior to biopsy were considered as having had antecedent treatment. Results We initially found no significant difference in the likelihood of a positive culture between patients who had received antecedent treatment and those who had not. However, when we performed a subgroup analysis, we found that using multiple antibiotics influenced the likelihood of a positive culture. A second subgroup analysis demonstrated that pre‐treatment reduced the likelihood of a positive culture. This discrepancy arose from the match between the antecedent antibiotics and the organisms’ antibiotic sensitivity profile. Conclusion Antibiotic treatment preceding CT‐guided biopsy reduces the likelihood of a positive microbiological culture results. However, due to the often poor match, between the pre‐treatment antibiotic and the organisms’ antibiotic sensitivity profile, this is often not clinically apparent. Furthermore, positive cultures sensitive to the pre‐treatment antibiotics can still be obtained.