No differences in serum levels of inflammatory biomarker levels were detected between individuals with leg pain related to low back pathology with or without sciatica or nerve root compression, according to a study published in BMC Musculoskeletal Disorders.

Sciatica pathogenesis may involve pro-inflammatory cytokines and other inflammatory mediators.

The Assessment and Treatment of Leg Pain Associated with the Spine (ATLAS) study was a single-site nested longitudinal cohort trial in which primary care patients >18 years of age who were seen by their general practitioner for low back-related leg pain were enrolled. A set of serum biomarkers were measured in a subsample of the cohort (n=119; 61.2% women). Participants underwent clinical evaluation, lumbar magnetic resonance imaging (MRI), and biomarker evaluations (for a set of 17 pro-inflammatory cytokines, matrix metalloproteinases, and chemokines, including tumor necrosis factor and interleukin-6) using multiplex detection kits and a Luminex suspension array system. The relationship between biomarker levels and clinical assessments was examined using multivariate logistic regression.

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Following clinical assessment, some patients were diagnosed with clinically defined sciatica (n=93; 78.2%) or referred leg pain (n=26; 21.8%; mean age, 49.5 years; 65% women). After undergoing MRI, patients diagnosed with sciatica were further divided according to the presence (n=44; 47.3%; mean age, 55.2 years; 55% women) or absence (n=49; 52.7%; mean age, 50.3 years; 65% women) of confirmed or probable nerve root compression secondary to disk prolapse.

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In participants with low back-related leg pain and sciatica, median biomarker levels were comparable in individuals with positive and negative MRI findings. After adjustment for potential confounders (ie, age, sex and duration of symptoms), no associations between any of the biomarkers examined and a sciatica diagnosis with or without MRI findings were established.

Study strengths include the use of an unselected primary care population, high generalizability, the use of both MRI and clinical examination, and consistent timing on biomarker sampling, thus mitigated biologic variability.

Study limitations include an inability to assess fluctuations in biomarker levels over time and the possible underpowering.

“These results suggest that in patients with low back-related leg pain, serum markers associated with inflammation do not discriminate between patients with or without clinically confirmed sciatica or between those with or without evidence of nerve root compression on MRI,” noted the authors. They recommended that future research involve longitudinal studies that examine cytokine levels in those with persistent symptoms and investigate whether other biomarkers might be pathogenetically relevant.

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Hider SL, Konstantinou K, Hay EM, Glossop J, Mattey DL. Inflammatory biomarkers do not distinguish between patients with sciatica and referred leg pain within a primary care population: results from a nested study within the ATLAS cohort. BMC Musculoskelet Disord. 2019;20(1):202.