title: Does patency after a vein collar and PTFE-bypass depend on sex and age? Re-analysis of a randomised trial.
abstract: OBJECTIVE
  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.
  
  
  CONCLUSIONS
  The difference between the two randomised vein collar studies are unlikely to depend on the disparity in sex and age of the study populations.
authors.affiliation: Scandinavian Miller Collar Study, University Hospital, Linköping, Sweden. fredrik.bg.lundgren@gmail.com
authors.forename: F
authors.initials: F
authors.lastname: Lundgren
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D001807:Blood Vessel Prosthesis; D019917:Blood Vessel Prosthesis Implantation / Q000009:adverse effects / Q000295:instrumentation*; D016009:Chi-Square Distribution; D005260:Female; D006083:Graft Occlusion, Vascular / Q000209:etiology / Q000503:physiopathology; D006801:Humans; D053208:Kaplan-Meier Estimate; D035002:Lower Extremity / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D058729:Peripheral Arterial Disease / Q000503:physiopathology / Q000601:surgery*; D011138:Polytetrafluoroethylene; D016016:Proportional Hazards Models; D011474:Prosthesis Design; D018570:Risk Assessment; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000009:adverse effects; D013997:Time Factors; D016896:Treatment Outcome; D014654:Vascular Patency; D014680:Veins / Q000601:surgery
chemical_list: D011138:Polytetrafluoroethylene