SNP in TNFα T308G is predictive for persistent postoperative pain following inguinal hernia surgery.

Aim of investigation Persistent postoperative pain of some extent is seen in about 20% of patients after surgical operations, while 80% heal without chronic pain. The type of chronic pain that arises is mainly neuropathic, and is suggested to be in part regulated by genetic factors. In order to study the possible involvement of some candidate genes suggested to be involved in the processing of pain (BDNF, CACNA2D2, ORPM1, GRIK 3, GCH1 and TNF-α ), we performed a genetic association study in a well characterized clinical material of patients that had undergone surgery for inguinal hernia (n = 189). Of those 94 had developed a persistent postoperative pain state when investigated 2-3 years following the operation. The control group (n = 95) had undergone the same surgical procedure, and were pain free at follow up. Methods Genomic DNA was extracted from blood samples and genotyped by the Handy Bio-strand method and the TaqMan assay. Results The patients with persistent postoperative pain that had homozygous SNP in the TNF-α gene displayed increased risk of persistent postoperative pain with an odds risk of 2.42, compared the pain free controls. None of the other of the investigated genes were associated with significant risk of development of chronic pain following surgery. Conclusion The expression of TNF-α shows a significant impact on the risk of developing chronic pain after surgery. Further experimental and clinical studies are needed in order to fine map the TNF-α effect and to address underlying mechanisms.