Using data linkage to enhance the reporting of cancer outcomes of Aboriginal and Torres Strait Islander people in NSW, Australia.
BACKGROUND
Aboriginal people are known to be under-recorded in routinely collected datasets in Australia. This study examined methods for enhancing the reporting of cancer incidence among Aboriginal people using linked data methodologies.


METHODS
Invasive cancers diagnosed in New South Wales (NSW), Australia, in 2010-2014 were identified from the NSW Cancer Registry (NSWCR). The NSWCR data were linked to the NSW Admitted Patient Data Collection, the NSW Emergency Department Data Collection and the Australian Coordinating Register Cause of Death Unit Record File. The following methods for enhancing the identification of Aboriginal people were used: 'ever-reported', 'reported on most recent record', 'weight of evidence' and 'multi-stage median'. The impact of these methods on the number of cancer cases and age-standardised cancer incidence rates (ASR) among Aboriginal people was explored.


RESULTS
Of the 204,948 cases of invasive cancer, 2703 (1.3%) were recorded as Aboriginal on the NSWCR. This increased with enhancement methods to 4184 (2.0%, 'ever'), 3257 (1.6%, 'most recent'), 3580 (1.7%, 'weight of evidence') and 3583 (1.7%, 'multi-stage median'). Enhancement was generally greater in relative terms for males, people aged 25-34 years, people with cancers of localised or unknown degree of spread, people living in urban areas and areas with less socio-economic disadvantage. All enhancement methods increased ASRs for Aboriginal people. The weight of evidence method increased the overall ASR by 42% for males (894.1 per 100,000, 95% CI 844.5-945.4) and 27% for females (642.7 per 100,000, 95% CI 607.9-678.7). Greatest relative increases were observed for melanoma and prostate cancer incidence (126 and 63%, respectively). ASRs for prostate and breast cancer increased from below to above the ASRs of non-Aboriginal people with enhancement of Aboriginal status.


CONCLUSIONS
All data linkage methods increased the number of cancer cases and ASRs for Aboriginal people. Enhancement varied by demographic and cancer characteristics. We considered the weight of evidence method to be most suitable for population-level reporting of cancer incidence among Aboriginal people. The impact of enhancement on disparities in cancer outcomes between Aboriginal and non-Aboriginal people should be further examined.
['Tervonen|Hanna E|HE|', 'Purdie|Stuart|S|', 'Creighton|Nicola|N|0000-0003-0959-6309']
D000293:Adolescent D000328:Adult D000368:Aged D000369:Aged, 80 and over D002648:Child D002675:Child, Preschool D005260:Female D006801:Humans D015994:Incidence D007223:Infant D007231:Infant, Newborn D016247:Information Storage and Retrieval D008297:Male D008498:Medical Record Linkage D008875:Middle Aged D044468:Native Hawaiian or Other Pacific Islander D009369:Neoplasms D009517:New South Wales D012042:Registries D055815:Young Adult
Data linkage Australia Indigenous Neoplasms