A Predictive Model Facilitates Early Recognition of Spinal Epidural Abscess in Adults

Implementation of an emergency department back pain clinical management tool on the early diagnosis and testing of spinal epidural abscess

BACKGROUND

Spinal epidural abscess (SEA) is a rare, catastrophic condition for which diagnostic delays are common. Our national group develops evidence-based guidelines, known as clinical management tools (CMT), to reduce high-risk misdiagnoses. We study whether implementation of our back pain CMT improved SEA diagnostic timeliness and testing rates in the emergency department (ED).

METHODS

We conducted a retrospective observational study before and after implementation of a nontraumatic back pain CMT for SEA in a national group. Outcomes included diagnostic timeliness and test utilization. We used regression analysis to compare differences before (January 2016-June 2017) and after (January 2018-December 2019) with 95% confidence intervals (CIs) clustered by facility. We graphed monthly testing rates.

RESULTS

In 59 EDs, pre versus post periods included 141,273 (4.8%) versus 192,244 (4.5%) back pain visits and 188 versus 369 SEA visits, respectively. After implementation, SEA visits with prior related visits were unchanged (12.2% vs. 13.3%, difference +1.0%, 95% CI -4.5% to 6.5%). Mean number of days to diagnosis decreased but not significantly (15.2 days vs. 11.9 days, difference -3.3 days, 95% CI -7.1 to 0.6 days). Back pain visits receiving CT (13.7% vs. 21.1%, difference +7.3%, 95% CI 6.1% to 8.6%) and MRI (2.9% vs. 4.4%, difference +1.4%, 95% CI 1.0% to 1.9%) increased. Spine X-rays decreased (22.6% vs. 20.5%, difference 2.1%, 95% CI -4.3% to 0.1%). Back pain visits receiving erythrocyte sedimentation rate or C-reactive protein increased (1.9% vs. 3.5%, difference +1.6%, 95% CI 1.3% to 1.9%).

CONCLUSIONS

Back pain CMT implementation was associated with an increased rate of recommended imaging and laboratory testing in back pain. There was no associated reduction in the proportion of SEA cases with a related prior visit or time to SEA diagnosis.

Spinal Epidural Abscess Patients Have Higher Modified Frailty Indexes Than Back Pain Patients on Emergency Room Presentation: A Single-Center Retrospective Case-Control Study

OBJECTIVE

Spinal epidural abscess (SEA) patients have increased medical comorbidities and risk factors for infection compared with those without SEA. However, the association between frailty and SEA patients has not been documented.

METHODS

A total of 46 SEA patients were randomly paired and matched by age and sex with a control group of patients with back pain who had presented to our emergency department from 2012 to 2017. Statistical analysis identified the risk factors associated with SEA and frailty using the modified frailty index (mFI), and the patients were stratified into robust, prefrail, and frail groups. We examined the value of the mFI as a prognostic predictor and evaluated the classic risk factors (CRFs).

RESULTS

The SEA patients had higher mFIs and CRFs (P = 0.023 and P < 0.001, respectively) and a longer length of stay (22.89 days vs. 1.72 days; P < 0.001). Of the mFI variables, only diabetes had a significant association with SEA (odds ratio [OR], 3.60; P = 0.012). Among the stratified mFI subgroups, a frail ranking (mFI >2) was the strongest risk factor for SEA (OR, 5.18; P = 0.003). A robust ranking (mFI, 0-1) was a weak negative predictor for SEA (OR, 0.41; P = 0.058). The robust patients were also more likely to be discharged to home (OR, 7.58; P = 0.002). Of the CRF variables, only intravenous drug use had a statistically significant association with SEA (OR, 10.72; P = 0.015).

CONCLUSIONS

Patients with SEA were more frail compared with the control back pain patients. Frailty was determined to be an independent risk factor for SEA, outside of the CRFs. The use of the mFI could be potentially useful in predicting the diagnosis, prognosticating, and guiding SEA treatment.

Role of C-reactive protein in effective utilization of emergent MRI for spinal infections

PURPOSE

Emergent spinal MRI is recommended for patients with back pain and red flags for infection. However, many of these studies are negative due to low prevalence of spinal infections. Our purpose was to assess if C-reactive protein (CRP) can be used to guide effective utilization of emergent MRI for spinal infections.

METHODS

316/960 (33%) MRIs performed for infection by the emergency department over 75-month period had CRP levels obtained at presentation, after excluding patients receiving antibiotic or had spinal surgery in < 1 month. An MRI was considered positive when there was imaging evidence of spinal infection confirmed on follow-up by surgery/biopsy/drainage or definitive therapy. A CRP of ≤ 10 mg/L was considered normal and > 100 mg/L as highly elevated.

RESULTS

CRP was normal in 95/316 (30%) and abnormal in 221/316 (70%) patients. MRI was positive in 43/316 (13.6%) patients, all of whom had abnormal CRP. CRP (p < 0.001) and intravenous drug use (IVDU; p = 0.002) were independently associated with a positive MRI. Receiver operator characteristic (ROC) analysis showed AUC of 0.76 for CRP, slightly improving with IVDU. Sensitivity, specificity, and negative predictive values for CRP level cut-off: 10 mg/L, 100%, 35%, and 100%, and 100 mg/L, 58%, 70% and 91%, respectively.

CONCLUSION

Abnormal CRP, although extremely sensitive, lacks specificity in predicting a positive MRI for spinal infection unless highly elevated. However, a normal CRP (absent recent antibiotic or surgery) makes spinal infection unlikely, and its routine use as a screening test can help reducing utilization of emergent MRI for this purpose.

Spinal epidural abscesses - The role for non-operative management: A systematic review

BACKGROUND

Spinal Epidural Abscesses (SEAs) are traditionally seen as a surgical emergency. However, SEAs can be discovered in entirely asymptomatic patients. This presents a dilemma for the attending clinician as to whether to subject these patients to significant surgery. This systematic review updates the evidence surrounding the efficacy of non-operative SEA management by means of intravenous antibiotics ± radiologically-guided aspiration.

AIMS

1. To assess failure rates of medical therapy for SEA. The absolute definition of 'failure' used by the study was recorded, and comparisons made. 2. To review of risk factors for success/failure of medical treatment for SEA.

METHODS

A database search with the MESH term 'epidural abscess' and keywords ['treatment' OR 'management'] were used.

RESULTS

14 studies were included. The number of SEA patients managed non-operatively ranged from 19 to 142. There was significant heterogeneity across the studies. Pooled Failure of Medical Therapy (FMT) (defined as any poor outcome) was 29.40%. When FMT = mortality the pooled rate was 11.49%. Commonly cited risk factors for FMT included acute neurological compromise, diabetes mellitus, increasing age and Staphylococcus aureus.

CONCLUSION

SEA will always be a condition mostly managed surgically. Despite this, there is growing evidence that non-operative management can be possible in the correct patients. The key is in patient selection - patients with any of the above-mentioned risk factors have the potential to deteriorate further on medical treatment and have a worse outcome than if they had undergone emergency surgery straight away. Ongoing research will hopefully further investigate this crucial step.