title: Patient registries of acute coronary syndrome: assessing or biasing the clinical real world data?
abstract: BACKGROUND
  The risk of selection bias in registries and its consequences are relatively unexplored. We sought to assess selection bias in a recent registry about acute coronary syndrome and to explore the way of conducting and reporting patient registries of acute coronary syndrome.
  
  
  RESULTS
  We analyzed data from patients of a national acute coronary syndrome registry undergoing an audit about the comprehensiveness of the recruitment/inclusion. Patients initially included by hospital investigators (n=3265) were compared to eligible nonincluded (missed) patients (n=1439). We assessed, for 25 exposure variables, the deviation of the in-hospital mortality relative risks calculated in the initial sample from the actual relative risks. Missed patients were of higher risk and received less recommended therapies than the included patients. In-hospital mortality was almost 3 times higher in the missed population (9.34% [95% CI, 7.84 to 10.85] versus 3.9% [95% CI, 2.89 to 4.92]). Initial relative risks diverged from the actual relative risks more than expected by chance (P<0.05) in 21 variables, being higher than 10% in 17 variables. This deviation persisted on a smaller degree on multivariable analysis. Additionally, we reviewed a sample of 129 patient registries focused on acute coronary syndrome published in thirteen journals, collecting information on good registry performance items. Only in 38 (29.4%) and 48 (37.2%) registries was any audit of recruitment/inclusion and data abstraction, respectively, mentioned. Only 4 (3.1%) authors acknowledged potential selection bias because of incomplete recruitment.
  
  
  CONCLUSIONS
  Irregular inclusion can introduce substantial systematic bias in registries. This problem has not been explicitly addressed in a substantial number of them.
authors.affiliation: Vall d'Hebron Hospital, Barcelona, Spain. nacho_ferreira@hotmail.com
authors.forename: Ignacio
authors.initials: I
authors.lastname: Ferreira-González
authors.forename: Josep R
authors.initials: JR
authors.lastname: Marsal
authors.forename: Francesca
authors.initials: F
authors.lastname: Mitjavila
authors.forename: Antoni
authors.initials: A
authors.lastname: Parada
authors.forename: Aida
authors.initials: A
authors.lastname: Ribera
authors.forename: Purificación
authors.initials: P
authors.lastname: Cascant
authors.forename: Núria
authors.initials: N
authors.lastname: Soriano
authors.forename: Pedro L
authors.initials: PL
authors.lastname: Sánchez
authors.forename: Fernando
authors.initials: F
authors.lastname: Arós
authors.forename: Magda
authors.initials: M
authors.lastname: Heras
authors.forename: Héctor
authors.initials: H
authors.lastname: Bueno
authors.forename: Jaume
authors.initials: J
authors.lastname: Marrugat
authors.forename: José
authors.initials: J
authors.lastname: Cuñat
authors.forename: Emilia
authors.initials: E
authors.lastname: Civeira
authors.forename: Gaietà
authors.initials: G
authors.lastname: Permanyer-Miralda
mesh_terms: D054058:Acute Coronary Syndrome / Q000453:epidemiology*; D000368:Aged; D054869:Clinical Audit; D017052:Hospital Mortality; D006801:Humans; D008875:Middle Aged; D018579:Patient Selection; D011786:Quality Control; D012042:Registries; D018570:Risk Assessment; D015983:Selection Bias; D013030:Spain