title: Estimation of the incidence of stroke using a capture-recapture model including covariates.
abstract: BACKGROUND
  Capture-recapture is often used to assess completeness of a register. However, the usual two-source model relies on assumptions of independence of sources and equality of capture probability which are rarely satisfied in epidemiology. An alternative is to include covariates in capture-recapture models.
  
  
  METHODS
  We use capture-recapture models including covariates to estimate incidence of stroke in South London. We estimate ascertainment-adjusted age-standardized incidence rates, and calculate confidence intervals for incidence which allow for the uncertainty in estimation of the total number of cases.
  
  
  RESULTS
  The crude capture-recapture model (including no covariates) underestimated the number of non-fatal strokes. Demographic and stroke severity variables were associated with the probability of capture. Including covariates led to more plausible results for fatal and non-fatal strokes, and suggested that the stroke register was 88% complete. Adjusting for under-ascertainment increased the estimated incidence from 1.31 (95% CI : 1.21-1.42) to 1.49 (95% CI : 0.38-2.60) per 1000 people.
  
  
  CONCLUSIONS
  Incidence and age-standardized incidence can be calculated using data from an incomplete register. However, sparse strata can lead to wide confidence intervals for adjusted rates. Cost-effectiveness of routine registers might be increased by using the combination of sources and covariates which most accurately estimates the total number of cases, rather than by aiming for 100% completeness.
authors.affiliation: Department of Public Health Sciences, King's College London, Capital House, 42 Weston Street, London SE1 3QD, UK. kate.tilling@kcl.ac.uk
authors.forename: K
authors.initials: K
authors.lastname: Tilling
authors.forename: J A
authors.initials: JA
authors.lastname: Sterne
authors.forename: C D
authors.initials: CD
authors.lastname: Wolfe
mesh_terms: D000368:Aged; D003625:Data Collection / Q000706:statistics & numerical data; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D015994:Incidence; D008131:London / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D012042:Registries / Q000706:statistics & numerical data*; D015203:Reproducibility of Results; D012720:Severity of Illness Index; D020521:Stroke / Q000453:epidemiology*