Quality of Case Ascertainment in Cancer Registries: A Proposal for a Virtual Three-source Capture-recapture Technique

Background: The ability and behaviour of the capture-recapture method using a virtual three-source modelfor evaluation of the level of completeness of case ascertainment requires exploration.
Methods: Cancer casesobtained from 9 population-based cancer registries in Thailand during 2003 to 2007 were applied for capturerecaptureusing a model based on clinical, pathological and mortality data. These three virtual sources werederived from three actual items common to all cancer registries: the basis of diagnosis, ICD-O morphologycode, and last known patient status. Poisson regression models were fit to the data to estimate parameterswhich were then transformed into demographic values. A linear model was used to determine the predictorsand estimated percentage of completeness (EPC) in case ascertainment among the cancer registries.
Results:The EPC was greater than 97% in 5 and less than 90% in 4 registries. The worst had an EPC of 70%. Thepercentage death certificate only (%DCO) and the interaction between %DCO and morphological verification(MV) were significantly associated with EPC. Other factors intrinsic to registries also exerted influence on theEPC.
Conclusions: In addition to other standard indicators to monitor completeness of cancer registries, thepresent virtual three-source capture-recapture model can be routinely used to estimate the level of completenessof case ascertainment in cancer registries.