The impact of antibiotic pre-treatment on diagnostic yield of CT-guided biopsy for spondylodiscitis: A multi-centre retrospective study and meta-analysis.

Introduction: Patients with suspected spondylodiscitis often undergo CT-guided biopsy to identify a causative microbiological organism. Antibiotic pre-treatment has been postulated as a cause for a negative biopsy, although previous clinical studies have been heterogenous with a meta-analysis suggesting no effect. The aim of this study was to assess the impact of antibiotic pre-treatment on microbiological yield.

Methods: Retrospective review of consecutive adult patients undergoing CT-guided biopsy for suspected spondylodiscitis in two tertiary centres between 2010 and 2016. Demographic, procedural and clinical data were collected. Antibiotic pre-treatment was ascertained from patient drug charts.

Results: Over the 6-year period, 104 biopsies in 104 patients were included. 51% had a positive microbiological yield at CT-guided biopsy, with the most common isolated organism being Staphylococcus aureus (10.6%). Over two thirds of patients (69.3%) were off antibiotics at time of biopsy. There was no significant difference in microbiological yield in those patients on versus off antibiotics (48.2% vs 54.2%, P = 0.55). 10.6% patients had a final diagnosis of Mycobacterium tuberculosis spondylodiscitis, and this organism was significantly associated with a positive microbiological yield (90.9% vs 46.2%, P = 0.01). There was an inverse association between the presence of fever and sepsis with positive microbiological yield.

Conclusions: CT-guided biopsy in suspected spondylodiscitis obtains a positive microbiological yield in about half of patients. This was significantly higher in patients diagnosed with tuberculosis spondylodiscitis, but there was no significant difference with antibiotic pre-treatment. Therefore, antibiotic pre-treatment should not preclude clinicians from pursuing a microbiological sample through CT-guided biopsy.