It cannot be overemphasized that up 50% of patients with spinal epidural abscess (SEA) have no known risk factors,  one-half may have no fever,  and 20-40% lack leukocytosis¹. In fact, the “classic triad” of back pain, fever, and neurological deficits is found only in the minority of patients!  No wonder that up to 75% of patients SEA are misdiagnosed on their initial healthcare encounter¹!

Potential “red flags” for infectious causes of low back pain include age >50 y, night pain, unremitting pain even when supine, duration > 6 weeks, fever, chills, night sweats, weight loss, conditions associated with Staphylococcus aureus bacteremia (eg intravenous drug use), incontinence, saddle anesthesia, and severe or rapidly progressive neurologic deficits^1,2.  

ESR and C-reactive protein (CRP) are almost uniformly elevated in SEA¹ and can serve as a good starting point in excluding this condition when in doubt.   In patients ≥50 y of age with low back pain, obtaining ESR routinely has been suggested for detection of systemic disease (eg cancer, infection)³.  Similarly, in a recent algorithm of severe back pain, routine measurements of ESR and CRP, even in the absence of any neurological findings, has been recommended¹; elevation of either may necessitate consideration of MRI.

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References:

1. Bond, A, Manian FA. Spinal epidural abscess: a review with special emphasis on earlier diagnosis. BioMed Res International 2016; https://www.hindawi.com/journals/bmri/2016/1614328/http://dx.doi.org/10.1155/2016/1614328  
2. Della-Giustina. Acute low back pain: recognizing the “red flags” in the workup. Consultant 2013;53:436-440. http://www.consultant360.com/article/acute-low-back-pain-recognizing-%E2%80%9Cred-flags%E2%80%9D-workup
3. Jarvik JG, Deyo RA. Diagnostic evaluation of low back pain with emphasis on imaging. Ann Intern Med 2002;137:586-597. http://annals.org/aim/article/715687/diagnostic-evaluation-low-back-pain-emphasis-imaging

Disclosures: The listed questions and answers are solely the responsibility of the author and do not necessarily represent the official views of Mercy Hospital-St. Louis or its affiliate healthcare centers, Mass General Hospital, Harvard Medical School or its affiliated institutions. Although every effort has been made to provide accurate information, the author is far from being perfect. The reader is urged to verify the content of the material with other sources as deemed appropriate and exercise clinical judgment in the interpretation and application of the information provided herein. No responsibility for an adverse outcome or guarantees for a favorable clinical result is assumed by the author. Thank you!

Additional disclosure: The author of this post (FAM) also coauthored reference 1.