Methodological issues in linking study participants to Australian cancer registries using different methods: lessons from a cohort study.
OBJECTIVE
To compare results of concurrent linkage of records from the same occupational cohort to cancer registries at both a State and national level. Methodological issues affecting the record registry linkage process will be explored in cases of discordant results between the State and national cancer linkages.


METHODS
The number of incident invasive cancers in an occupational cohort of more than 11,000 workers was determined by linkage to the National Cancer Statistics Clearing House (NCSCH) in 2003. The results were then compared with linkages by the cancer registries of Victoria and Western Australia in 2004, and also with a previous NCSCH linkage in 1998.


RESULTS
Our analyses show an under-ascertainment of confirmed cancer cases by the NCSCH of about 13% (26/205) in Victoria and 11% (32/297) in Western Australia. In addition, 14 cases (5%) identified in a previous NCSCH record linkage in 1998 were not matched in 2003.


CONCLUSIONS
These findings strongly indicate that record linkage to the State cancer registries was essential to maximise the ascertainment of cancer cases in our cohort. We attribute the discordant linkage results to differences in the quality of the record linkage process by the cancer registries.


CONCLUSIONS
The record linkage methods of the national and State cancer registries need further standardisation. At present it is advisable to perform cancer record linkages through the State registries in addition to or instead of the NCSCH.
Hoving
Jan Lucas
JL
Department of Epidemiology and Preventive Medicine, Central and Eastern Clinical School, Alfred Hospital, Monash University, Victoria.
Del Monaco
Anthony
A
MacFarlane
Ewan
E
Fritschi
Lin
L
Benke
Geza
G
McKenzie
Dean
D
Sim
Malcolm
M
D001315:Australia / Q000453:epidemiology; D015331:Cohort Studies; D003628:Database Management Systems; D015340:Epidemiologic Research Design; D006801:Humans; D015994:Incidence; D008498:Medical Record Linkage / Q000379:methods* / Q000592:standards; D009369:Neoplasms / Q000453:epidemiology*; D012042:Registries / Q000592:standards / Q000706:statistics & numerical data*; D014739:Victoria / Q000453:epidemiology; D014904:Western Australia / Q000453:epidemiology