Journal Club

Hold Those Antibiotics! Improving Yield of Biopsy in Vertebral Osteomyelitis

By Christopher J. Graber, MD, MPH, FIDSA

Diagnosis of the etiologic agent of vertebral osteomyelitis is often difficult. The most common method of diagnosis is via image-guided biopsy, typically by interventional radiologists or neuroradiologists, with biopsy material sent for culture. However, many factors can impact the positivity of these cultures, most notably prior antimicrobial therapy.

In a study recently published in Open Forum Infectious Diseases, authors affiliated with the Mayo Clinic described their 10-year experience with image-guided biopsy of suspected vertebral osteomyelitis. Among 209 initial image-guided biopsies, only 110 (52.6%) yielded positive microbiologic results. Repeat biopsies were positive in 14 out of 39 (35.9%) patients. In multivariable analysis, aspiration of fluid was associated with increased microbiologic yield (odds ratio [OR], 3.13; 95% confidence interval [CI], 1.39-7.04), while prior antibiotic use was associated with decreased yield (OR, 0.32; 95% CI, 0.16-0.65). Microbiologic yield only improved above 50% with at least 3 antibiotic-free days prior to biopsy, increasing up to 75% around day 12.

This work provides important perspective to a common clinical situation. When possible clinically, antibiotics should be held prior to biopsy, with the longer the interval between antibiotic receipt and biopsy, the better. Fluid collections should be aspirated wherever possible. However, the overall poor yield of biopsy suggests a need for more thorough evaluation of other diagnostic modalities in vertebral osteomyelitis (e.g., 16S sequencing, detection of bloodstream microbial cell-free DNA); repeat biopsy when the initial biopsy is negative may also be of value. 

(Maamari et al. Open Forum Infect Dis. Published online: Nov. 16, 2022.)