Is the interleukin-6 haplotype a prognostic factor for sciatica?

We have shown in a cross-sectional setting that an IL6 haplotype (GGGA) is associated with intervertebral disc disease (IDD) characterized by sciatica. The aim of this study was to evaluate the prognostic role of the GGGA haplotype in IDD.

DNA from 153 sciatica patients who participated in a randomized controlled trial of periradicular infiltration was analysed for IL6 variations rs1800797 (-596A>G), rs1800796 (-572G>C), rs1800795 (-174G>C), and rs13306435 (+15T>A). The patients recorded back and leg pain intensity and duration, disability by Oswestry Index and back-related sickness absence over a three-year follow-up. Repeated measures and univariate analysis of variance with adjustment for age, gender and physical work load were used in statistical analyses for the last two-years of the follow-up.

The prevalence of the GGGA haplotype was 9% (14/153). Subjects with the GGGA haplotype did not differ from those without the haplotype with respect to pain intensity, or disability score, but days with back and leg pain and days on sick leave were significantly higher among subjects with the IL6 haplotype after adjustment for occupation (p=0.006, 0.001 and 0.002, respectively). An interaction between the IL6 haplotype and physical work load was significant for the duration of back and leg pain and sick leave (p=0.038, 0.011 and 0.006, respectively).

This is the first observation of any prognostic genotype among sciatica patients. The IL6 haplotype GGGA predicted the number of days with back or leg pain and also sickness absence. Subjects with the IL6 haplotype may be more vulnerable when doing physically demanding jobs.