Aim: Randomized studies evaluating the effect of a vein collar at the distal anastomosis of PTFE-grafts show conflicting results. The study of the Joint Vascular Research Group (JVRG) of UK found improved primary patency while the Scandinavian Miller Collar Study (SCAMICOS) found neither any effect on patency nor on limb salvage after bypass to below-knee arteries. However, the Scandinavian patients were a decade older and predominately female compared to the British patients. Can this explain the conflicting result?
Methods: Primary patency with respect to sex, age and the use of vein collar were re-analysed in 345 patients from SCAMICOS with Kaplan-Meier life-table technique, log-rank test and Cox proportional hazards regression to evaluate any interaction between sex or age and the effect of a vein collar on the primary patency rate.
Results: Females had better patency than males (log-rank test, χ2=9.4, df=1, P=0.002) but age had no influence on patency (log-rank test, χ2=3.3, df=3, P=0.35). However, 47% of the males compared to 23% of the females were smokers (P=0.00002). No interaction effect between sex and vein collar (P-value=0.224) or age and vein collar (P-value=0.527) was established.
Conclusion: The difference between the two randomised vein collar studies are unlikely to depend on the disparity in sex and age of the study populations.