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Published on: September 11, 2017
A Prospective Clinical Study Correlating Serum Interleukin-6 levels and IL-6 Gene Polymorphisms with the Outcome
Nasim Mansoori1, Amol Raheja1, Sumit Sinha2
1Department of Neurosurgery, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India.
Background:
The outcome after severe traumatic brain injury (STBI) is a multifactorial process. We assessed the correlation of serum IL-6 levels and IL-6-174 G/C polymorphisms with long-term functional outcome after STBI.
Methods:
Serum IL-6 was measured by ELISA technique. IL-6-174 G/C gene polymorphisms were assessed using PCR-RFLP in STBI patients between 18 and 65 years. The functional outcome (Glasgow Outcome Scale, GOS and Functional Independence Measure, FIM) was evaluated at 1, 6, and 12 months after injury.
Results:
62 consecutive patients (mean age 33.8 ± 11.6 years) with STBI were recruited for the study. There was a statistically significant reduction of serum IL-6 levels after 1 week of injury in both wild (GG) and variant (GC and CC) genotypes (p=<0.0001 and P = 0.001, respectively); however, there was no significant variation of serum IL-6 levels among the two genotypes at any time point (P = 0.97 and P = 0.84 at admission and day 7, respectively). Intragenotype analysis demonstrated a statistically significant improvement in outcome parameters (GOS and FIM) till 6 months after injury in both the wild (P = 0.0001 and p=<0.0001) and variant (P = 0.0002 and P = 0.0005) genotypes. While a significant improvement of FIM was evident between 6 and 12 months (P = 0.003 and P = 0.02 for wild and variant types respectively), the recovery pattern plateaued for the GOS with no significant improvement over the next 6 months (P = 0.08 for wild type and P = 0.16 for variant type, respectively, for 6-month and 12-month time intervals). Inter-genotype analysis demonstrated no significant difference in outcome (GOS and FIM) between wild and variant types at any time point (1-month, 6-month, and 12-month time periods; P > 0.05). Multivariate logistic regression model failed to identify IL-6 genetic polymorphism (P = 0.81 and P = 0.99) and serum IL-6 levels (P = 0.54 and P = 0.69) as independent risk factors for outcome (GOS and FIM) at 1 year. Admission GCS was the only significant (P = 0.04) independent risk factor for FIM outcome after 1 year of injury in the present cohort.
Conclusion:
We could not find any significant association of IL-6-174 G/C polymorphism and serum IL-6 levels with long-term outcome after STBI. Besides, contrary to our expectations, there was no difference in serum IL-6 levels among the two genotypic groups. The underlying mechanisms behind the observed findings are unclear and need to be further studied.
