What is the diagnostic yield of disc space aspiration performed by interventional radiology (IR) for the diagnosis of discitis?

From the Guidelines

The yield of disc space aspiration by interventional radiology for the diagnosis of discitis is generally low to moderate, ranging from 30-50% in most clinical settings. This procedure involves using image guidance (typically CT or fluoroscopy) to obtain a sample from an infected intervertebral disc for microbiological analysis, as recommended by the 2015 Infectious Diseases Society of America (IDSA) clinical practice guidelines for the diagnosis and treatment of native vertebral osteomyelitis in adults 1. The relatively low yield is due to several factors, including prior antibiotic administration, the small volume of obtainable fluid, the indolent nature of many disc infections, and the presence of biofilms that make organisms difficult to culture.

The yield may be improved by collecting both aerobic and anaerobic cultures, using blood culture bottles for specimen collection, performing PCR testing when available, and ensuring adequate sampling technique, as suggested by the 2015 IDSA guidelines 1. Despite the modest yield, disc aspiration remains an important diagnostic tool because when positive, it provides definitive identification of the causative organism and guides targeted antibiotic therapy. This procedure is most valuable in cases where blood cultures are negative and empiric therapy has been ineffective, or when unusual pathogens such as fungi or tuberculosis are suspected, as noted in the 2021 ACR Appropriateness Criteria for suspected spine infection 1.

The diagnostic yield must be weighed against the small but real risks of the procedure, including bleeding, nerve injury, and introducing infection. According to the 2021 ACR Appropriateness Criteria, MRI spine area of interest without and with IV contrast is often utilized for the evaluation of patients with suspected spine infection, with a sensitivity, specificity, and accuracy of 96%, 94%, and 92%, respectively 1. However, the yield of disc space aspiration is generally lower, ranging from 30-50% in most clinical settings, as reported in various studies 1.

In summary, disc space aspiration by interventional radiology is a valuable diagnostic tool for discitis, despite its relatively low yield, and should be considered in cases where blood cultures are negative and empiric therapy has been ineffective, or when unusual pathogens are suspected. The procedure should be performed with careful consideration of the potential risks and benefits, and in conjunction with other diagnostic modalities, such as MRI, to guide targeted antibiotic therapy and improve patient outcomes.

From the Research

Diagnostic Yield of Disc Space Aspiration

• The diagnostic yield of disc space aspiration by interventional radiology for the diagnosis of discitis has been studied in several research papers 2, 3, 4, 5.
• A study published in Radiology in 2001 found that microbiologic analysis of CT-guided percutaneous aspiration specimens was positive in 39 of 43 cases proved to have active infections, with a sensitivity of 91% and specificity of 100% 2.
• Another study published in Current problems in diagnostic radiology in 2022 compared CT-guided bone biopsy and fluoroscopic-guided disc aspiration as diagnostic methods in the management of spondylodiscitis, and found that both modalities have similar utility in isolating causative organisms, with a yield of 34% and 32% respectively 3.
• A study published in the British journal of neurosurgery in 2023 found that the overall positive diagnostic yield of image-guided percutaneous sampling of intervertebral disc was 35%, and that including disc material in the sample significantly improved the diagnostic yield to 47% 4.
• A review article published in the AJR. American journal of roentgenology in 2021 reported that the yield of CT-guided percutaneous sampling is 31-91%, and discussed technical factors that may improve microbiologic yield, such as anatomic approach, needle selection, and needle angulation 5.

Factors Affecting Diagnostic Yield

• The use of antibiotics before biopsy may affect the diagnostic yield, but a study found that it did not seem to affect the likelihood of obtaining a positive yield 4.
• The inclusion of disc material in the sample has been shown to improve the diagnostic yield 4.
• Technical factors such as anatomic approach, needle selection, and needle angulation may also improve microbiologic yield 5.

Comparison with Other Diagnostic Methods

• A study compared CT-guided percutaneous aspiration with open surgery, and found that CT-guided percutaneous aspiration is an accurate method for identifying active bacterial disk space infections, but is less reliable for identifying fungal infections 2.
• Another study compared CT-guided bone biopsy and fluoroscopic-guided disc aspiration, and found that both modalities have similar utility in isolating causative organisms, but that CT-guided bone biopsy required more general anesthesia, had longer radiation exposure time, and longer procedure time 3.