FDG PET is a robust tool for the diagnosis of spondylodiscitis: A meta-analysis of diagnostic data

PURPOSE: Spondylodiscitis is a rare infectious entity that requires multimodal diagnostic procedures. We evaluated the diagnostic performance of ¹⁸F-FDG PET on suspected spondylodiscitis based on published literature. PATIENTS AND METHODS: We searched the PubMed and EMBASE for pertinent studies up to July 2013. We implemented a patient-based meta-analysis of diagnostic data for FDG PET (the index test) against clinical, laboratory, and/or radiologic evidence of disease (the reference standard). A bivariate analysis was implemented to account for variability beyond the threshold effect. The individual patient data analysis was used to assess confounding factors that moderate diagnostic performance. RESULTS: Twelve studies provided the diagnostic data on FDG PET and spondylodiscitis, comprising 224 patients. The combined sensitivity across studies was 0.97 [95% confidence interval (CI), 0.83-1.00], the specificity was 0.88 (95% CI, 0.74-0.95), and the area under the curve was 0.98 (95% CI, 0.96-0.99). For prior probabilities greater than 0.50, the corresponding positive predictive value was 0.96 (0.93-0.98), and the negative predictive value was 0.85 (0.82-0.88). In the individual patient data analysis, metallic implants, dual PET/CT scanners and the addition of other imaging modalities to confirm disease were significant outcome moderators; only PET/CT remained significant in the adjusted analysis. PET/CT scanners improved the diagnostic performance, as opposed to the clinical data (age, sex, lesion site), which did not alter outcome. CONCLUSIONS: FDG PET is a robust diagnostic test when spondylodiscitis is suspected and is excellent for exclusion of infectious spondylodiscitis given its low likelihood ratio negative (<0.1). Importantly, this diagnostic test is unaffected by other confounders, including the presence of implants, when PET/CT is used.