Imaging characteristics and CT sensitivity for pyogenic spinal infections.

BACKGROUND/OBJECTIVE: Contrast-enhanced magnetic resonance imaging (MRI) is the preferred imaging modality for diagnosing pyogenic spinal infection (PSI), but it is not always available. Our objective was to describe pyogenic spinal infection imaging characteristics in patients presenting to a community emergency department (ED) and estimate the computed tomography (CT) sensitivity for these infections. METHODS: We examined the MRI reports from a cohort of 88 PSI patients whom we enrolled in a prospective cohort study and report the prevalence of each PSI type (spinal epidural abscess/infection, vertebral osteomyelitis/discitis, septic facet, and paravertebral abscess/infection) according to contemporary nomenclature. In a 14 patient subcohort who underwent both CT and MRI studies, we report the sensitivity for each PSI from a post hoc blinded overread of the CT imaging by a single neuroradiologist. RESULTS: Of the 88 PSI patients, the median age was 55 years, and 31% were female. The PSI prevalence included: spinal epidural abscess/infection (SEA) in 61(69%), vertebral osteomyelitis/discitis (VO/D) in 54 (61%), septic facet (SF) in 15 (17%), and paravertebral abscess/infection (PVA) in 53 (60%). Of the SEAs, 82% (50/61) were associated with other spinal infections, while 18% (11/61) were isolated SEAs. The overall CT sensitivity in a masked overread was 79% (11/14) for any PSI, 83% (10/12) for any infection outside the spinal canal, and only 18% (2/11) for SEA. CONCLUSION: Patients found to have vertebral osteomyelitis/discitis, septic facet, and paravertebral infections frequently had a SEA coinfection. CT interpretation by a neuroradiologist had moderate sensitivity for infections outside the spinal canal but had low sensitivity for SEA.

A Clinical Prediction Tool for MRI in Emergency Department Patients with Spinal Infection.

INTRODUCTION: Patients with pyogenic spinal Infection (PSI) are often not diagnosed at their initial presentation, and diagnostic delay is associated with increased morbidity and medical-legal risk. We derived a decision tool to estimate the risk of spinal infection and inform magnetic resonance imaging (MRI) decisions. METHODS: We conducted a two-part prospective observational cohort study that collected variables from spine pain patients over a six-year derivation phase. We fit a multivariable regression model with logistic coefficients rounded to the nearest integer and used them for variable weighting in the final risk score. This score, SIRCH (spine infection risk calculation heuristic), uses four clinical variables to predict PSI. We calculated the statistical performance, MRI utilization, and model fit in the derivation phase. In the second phase we used the same protocol but enrolled only confirmed cases of spinal infection to assess the sensitivity of our prediction tool. RESULTS: In the derivation phase, we evaluated 134 non-PSI and 40 PSI patients; median age in years was 55.5 (interquartile range [IQR] 38-70 and 51.5 (42-59), respectively. We identified four predictors for our risk score: historical risk factors; fever; progressive neurological deficit; and C-reactive protein (CRP) ≥ 50 milligrams per liter (mg/L). At a threshold SIRCH score of ≥ 3, the predictive model's sensitivity, specificity, and positive predictive value were, respectively, as follows: 100% (95% confidence interval [CI], 100-100%); 56% (95% CI, 48-64%), and 40% (95% CI, 36-46%). The area under the receiver operator curve was 0.877 (95% CI, 0.829-0.925). The SIRCH score at a threshold of ≥ 3 would prompt significantly fewer MRIs compared to using an elevated CRP (only 99/174 MRIs compared to 144/174 MRIs, P <0.001). In the second phase (49 patient disease-only cohort), the sensitivities of the SIRCH score and CRP use (laboratory standard cut-off 3.5 mg/L) were 92% (95% CI, 84-98%), and 98% (95% CI, 94-100%), respectively. CONCLUSION: The SIRCH score provides a sensitive estimate of spinal infection risk and prompts fewer MRIs than elevated CRP (cut-off 3.5 mg/L) or clinician suspicion.

Sensitivity of C-reactive protein cut-off values for pyogenic spinal infection in the emergency department.

OBJECTIVES: The aim of this study was to describe the sensitivity of various C-reactive protein (CRP) cut-off values to identify patients requiring magnetic resonance imaging evaluation for pyogenic spinal infection among emergency department (ED) adults presenting with neck or back pain. METHODS: We prospectively enrolled a convenience series of adults presenting to a community ED with neck or back pain in whom ED providers had concern for pyogenic spinal infection in a derivation cohort from 2004 to 2010 and a validation cohort from 2010 to 2018. The validation cohort included only patients with pyogenic spinal infection. We analysed diagnostic test characteristics of various CRP cut-off values. RESULTS: We enrolled 232 patients and analysed 201 patients. The median age was 55 years, 43.8% were male, 4.0% had history of intravenous drug use, and 20.9% had recent spinal surgery. In the derivation cohort, 38 (23.9%) of 159 patients had pyogenic spinal infection. Derivation sensitivity and specificity of CRP cut-off values were > 3.5 mg/L (100%, 24.8%), > 10 mg/L (100%, 41.3%), > 30 mg/L (100%, 61.2%), and > 50 mg/L (89.5%, 69.4%). Validation sensitivities of CRP cut-off values were > 3.5 mg/L (97.6%), > 10 mg/L (97.6%), > 30 mg/L (90.4%), and > 50 mg/L (85.7%). CONCLUSIONS: CRP cut-offs beyond the upper limit of normal had high sensitivity for pyogenic spinal infection in this adult ED population. Elevated CRP cut-off values of 10 mg/L and 30 mg/L require validation in other settings.

High risk clinical characteristics for pyogenic spinal infection in acute neck or back pain: Prospective cohort study.

OBJECTIVE: To identify clinical characteristics associated with pyogenic spinal infection among adults presenting to a community emergency department (ED) with neck or back pain. A secondary objective was to describe the frequency of these characteristics among patients with spinal epidural abscess (SEA). METHODS: We conducted a prospective cohort study in a community ED enrolling adults with neck or back pain in whom the ED provider had clinical concern for pyogenic spinal infection. Study phase 1 (Jan 2004-Mar 2010) included patients with and without pyogenic spinal infection. Phase 2 (Apr 2010-Aug 2018) included only patients with pyogenic spinal infection. We performed univariate and multivariate analyses for association of clinical characteristics with pyogenic spinal infection. RESULTS: We enrolled 232 and analyzed 223 patients, 89 of whom had pyogenic spinal infection. The median age was 55 years and 102 patients (45.7%) were male. The clinical characteristics associated with pyogenic spinal infection on multivariate analysis of study phase 1 included recent soft tissue infection or bacteremia (OR 13.5, 95% CI 3.6 to 50.7), male sex (OR 5.0, 95% CI 2.5 to 10.0), and fever in the ED or prior to arrival (OR 2.8, 95% CI 1.3 to 6.0). Among patients with SEA (n = 61), 49 (80.3%) had at least one historical risk factor, 12 (19.7%) had fever in the ED, and 8 (13.1%) had a history of intravenous drug use. CONCLUSION: Male sex, fever, and recent soft tissue infection or bacteremia were associated with pyogenic spinal infection in this prospective ED cohort.