Serum levels of the pro-inflammatory interleukins 6 (IL-6) and -8 (IL-8) in patients with lumbar radicular pain due to disc herniation: A 12-month prospective study

Earlier studies indicate that lumbar radicular pain after disc herniation may be associated with a local inflammation induced by leakage of nucleus pulposus (NP) into the spinal canal and neuroforamen. In the present study we addressed the role of two interleukins, IL-6 and IL-8 in such long-lasting lumbar radicular pain. All 127 patients were recruited from Oslo University Hospital, Ullevål, Norway. At inclusion, 6 weeks and 12 months, serum concentrations of IL-6 and IL-8 were analyzed by enzyme-linked immunosorbent assay (ELISA) and pain intensity was reported on a 0-10 cm visual analog scale (VAS). Significantly higher levels of IL-6 and IL-8 in serum were found in patients with VAS ⩾3 at 12 months, than in patient with VAS <3 at 12 months (p ⩽ 0.01, test of between-subjects effect, repeated measures ANOVA, covariates for IL-6: age, smoking; covariates for IL-8: smoking, treatment). For the first time we show that chronic lumbar radicular pain may be associated with a persistent increase of the pro-inflammatory substances IL-6 and IL-8 in serum after disc herniation.