• Kylie Lopes Floro, Wendy Munckhof, and John Coucher.
• Department of Radiation Oncology, The Townsville Hospital, Townsville, Queensland, Australia.
• J Med Imaging Radiat Oncol. 2018 Jun 1; 62 (3): 307-312.

IntroductionPatients 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.MethodsWe 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.ResultsWe 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.ConclusionAntibiotic 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.© 2017 The Royal Australian and New Zealand College of Radiologists.

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