The role of repeat CT-guided biopsy in suspected infectious spondylodiscitis

This retrospective observational study assesses the diagnostic yield of CT-guided disc-vertebral biopsies in patients with suspected infectious spondylodiscitis. It focuses on the utility of a second biopsy after an initial negative result and evaluates factors associated with microbiological positivity.

It included adult patients undergoing CT-guided biopsies between January 2019-June 2024 at a single tertiary care center. The exclusion criteria were as follows: non-infectious indications (e.g., metastases, primary bone tumors, and crystal deposition disease) or biopsy results inconsistent with infection.

In total, 93 biopsies were analyzed in 79 patients: 79 first and 14 repeat biopsies. The microbiological yield of first biopsies was 53.2% (42/79; 95% CI 42.3-63.8), while repeat biopsies yielded positive results in 35.7% (5/14; 95% CI 16.3-61.2), increasing the overall diagnostic yield to 59.5% (47/79). The diagnostic yield of repeat biopsies did not significantly differ from first biopsies (p = 0.36). Higher C-reactive protein (CRP) levels were associated with positive results (median 40 vs 20 mg/L; p = 0.008; adjusted OR 1.57 per unit increase in log-transformed CRP, p = 0.043). No association was found with age, gender, or leukocyte count. Blood cultures were positive in 7.8% (7/90) and showed high concordance with biopsy findings (6/7 matching pathogens). In post-surgical infections, the diagnostic yield reached 80% (4/5).

A negative initial biopsy did not preclude microbiological identification on repeat sampling, supporting the role of repeat biopsy in selected patients with persistent suspicion of infection. Higher CRP levels were associated with biopsy positivity.