title: [Study on the significance and application of crossover analysis in assessing gene-environmental interaction].
abstract: OBJECTIVE
  To examine the significance of crossover analysis in gene-environmental interaction studies.
  
  
  METHODS
  Through elaboration of a case-control study on the increased risk of venous thrombosis in oral-conceptive users who were carriers of factor V Leiden mutation, core information from 2 x 4 crossover table were analyzed and compared with stratified analysis and 'case only' study.
  
  
  RESULTS
  Different models (additive or multiplicative) in analyzing gene-environmental interaction yielded different results. The result of interaction based on multiplicative model was 1.35 (P > 0.05), compatible with that of stratified analysis and case only study. Calculated by crossover analysis based on additive model, synergy index S(S), attributable proportion of interaction (AP) and relative excess risk of interaction (RERI) appeared to be 3.90, 72.24%, 25.08 (P > 0.05) respectively.
  
  
  CONCLUSIONS
  Crossover analysis should further be applied in gene-environmental interaction studies.
authors.affiliation: Department of Epidemiology and Statistics, School of Public Health, Nanjing Medical University, Nanjing 210029, China.
authors.forename: Pei-hua
authors.initials: PH
authors.lastname: Wang
authors.forename: Hong-bing
authors.initials: HB
authors.lastname: Shen
authors.forename: Feng
authors.initials: F
authors.lastname: Chen
authors.forename: Jin-kou
authors.initials: JK
authors.lastname: Zhao
mesh_terms: D016022:Case-Control Studies; D003276:Contraceptives, Oral / Q000009:adverse effects; D018592:Cross-Over Studies; D004777:Environment; D005165:Factor V / Q000235:genetics; D005260:Female; D005819:Genetic Markers; D005838:Genotype; D006801:Humans; D009154:Mutation; D012307:Risk Factors; D020246:Venous Thrombosis / Q000139:chemically induced / Q000235:genetics*
chemical_list: D003276:Contraceptives, Oral; D005819:Genetic Markers; C095381:factor V Leiden; D005165:Factor V