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

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.

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.

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.

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.