title: Sensitivity to biases of case-control studies on medical procedures, particularly surgery and blood transfusion, and risk of Creutzfeldt-Jakob disease.
abstract: BACKGROUND
  Evidence of risk of Creutzfeldt-Jakob disease (CJD) associated with medical procedures, including surgery and blood transfusion, is limited by susceptibility to bias in epidemiological studies.
  
  
  METHODS
  Sensitivity to bias was explored using a central-birth-cohort model using data from 18 case-control studies obtained after a review of 494 reports on medical procedures and risk of CJD, systematic for the period January 1, 1989 to December 31, 2011.
  
  
  RESULTS
  The validity of the findings in these studies may have been undermined by: recall; control selection; exposure assessment in life-time periods of different duration, out of time-at-risk of effect, or asymmetry in case/control data; and confounding by concomitant blood transfusion at the time of surgery. For sporadic CJD (sCJD), a history of surgery or blood transfusion was associated with risk in some, but not all, recent studies at a ≥10 year lag time, when controls were longitudinally sampled. Space-time aggregation of surgical events was not seen. Surgery at early clinical onset might be overrepresented among cases. Neither surgical history nor blood transfusion unlabelled for donor status, dental treatments or endoscopic examinations were linked to variant CJD (vCJD).
  
  
  CONCLUSIONS
  These results indicate the need for further research. Common challenges within these studies include access to and content of past medical/dental treatment records for diseases with long incubation periods.
authors: Department of Applied Epidemiology, National Centre for Epidemiology and Consortium for Biomedical Research in Neurodegenerative Diseases, Carlos III Institute of Health, Madrid, Spain. jpedro@isciii.es
authors: Jesús
authors: J
authors: de Pedro Cuesta
authors: María
authors: M
authors: Ruiz Tovar
authors: Hester
authors: H
authors: Ward
authors: Miguel
authors: M
authors: Calero
authors: Andrew
authors: A
authors: Smith
authors: Concepción Alonso
authors: CA
authors: Verduras
authors: Maurizio
authors: M
authors: Pocchiari
authors: Marc L
authors: ML
authors: Turner
authors: Frode
authors: F
authors: Forland
authors: Daniel
authors: D
authors: Palm
authors: Robert G
authors: RG
authors: Will
mesh_terms: D015982:Bias; D001803:Blood Transfusion / Q000706:statistics & numerical data*; D016022:Case-Control Studies; D007562:Creutzfeldt-Jakob Syndrome / Q000453:epidemiology* / Q000635:transmission; D006801:Humans; D012307:Risk Factors; D013514:Surgical Procedures, Operative / Q000706:statistics & numerical data*