title: Classification of surgical procedures for epidemiologic assessment of sporadic Creutzfeldt-Jakob disease transmission by surgery.
abstract: BACKGROUND
  In this preparatory phase of a case-control study, we propose and evaluate a new tool for classifying surgical procedures (SPs) in categories useful for epidemiologic research on surgical transmission of sporadic Creutzfeldt-Jakob disease (sCJD).
  
  
  METHODS
  All SPs reported to the Swedish National Hospital Discharge Registry in the period 1974-2002, and undergone by 212 Swedish patients with registered diagnosis of CJD at death, hospital discharge or notification, in the period 1987-2002, 1060 age-, sex- and residence-matched controls and 1340 randomly chosen population controls, were reclassified into one of six categories of hypothetical transmission risk level. For that purpose the following two attributes were used: non-disposable instruments involved; and highest assigned ad-hoc risk level for four tissues or anatomical structures contacting such instruments.
  
  
  RESULTS
  A total of 1170 different SP codes were reclassified as follows: 3.1% in the high-risk, 59.1% in the lower-risk, 24.4% in the lowest-risk, and 2.1% in the no-risk groups, with 11.3% procedures negatively defined by rubric as "other than..." being assigned to two spurious diluted-high and diluted-lower risk categories. The high-risk group mainly comprised neurosurgical (53%) and ophthalmic (39%) procedures. Sensitivity of neurosurgery and of ophthalmic surgery excluding neurosurgery, for the high- and diluted-high risk vs. other categories was 46% and 84%, while specificity was 98% and 95%, respectively. Sensitivity analysis based on these indices revealed that non-significant odds ratio effects of 1.4 and 1.3 for neurosurgery and ophthalmic surgery corresponded to statistically significant values of 5.1 after reclassification.
  
  
  CONCLUSIONS
  This classification might contribute to quantify effects masked by use of body-system SP-categories in case-control studies on sCJD transmission by surgery.
authors.affiliation: Department of Applied Epidemiology, National Center for Epidemiology, Carlos III Institute of Health, C/Sinesio Delgado 6, 28029 Madrid, Spain. jpedro@isciii.es
authors.forename: J
authors.initials: J
authors.lastname: de Pedro-Cuesta
authors.forename: M J
authors.initials: MJ
authors.lastname: Bleda
authors.forename: A
authors.initials: A
authors.lastname: Rábano
authors.forename: M
authors.initials: M
authors.lastname: Cruz
authors.forename: H
authors.initials: H
authors.lastname: Laursen
authors.forename: K
authors.initials: K
authors.lastname: Mølbak
authors.forename: A
authors.initials: A
authors.lastname: Siden
mesh_terms: D016022:Case-Control Studies; D007562:Creutzfeldt-Jakob Syndrome / Q000453:epidemiology* / Q000209:etiology / Q000635:transmission*; D006801:Humans; D018570:Risk Assessment; D012307:Risk Factors; D013525:Surgical Instruments; D013514:Surgical Procedures, Operative / Q000009:adverse effects* / Q000145:classification* / Q000379:methods