Aboriginal and non-Aboriginal sexually transmitted infections and blood borne virus notification rates in Western Australia: using linked data to improve estimates

BACKGROUND: National notification data for sexually transmitted infections (STIs) and blood borne viruses (BBVs) continue to have a high proportion of missing data on Indigenous status, potentially biasing estimates of notification rates by Aboriginality. We evaluated the use of data linkage to improve the accuracy of estimated notification rates for STIs and BBVs in Aboriginal and non-Aboriginal groups in Western Australia. METHODS: STI and BBV case notifications in Western Australia received in 2010 were linked with administrative health data collections in Western Australia to obtain additional data on Indigenous status. STI and BBV notification rates based on the pre- and post-linkage data among Aboriginal and non-Aboriginal groups were compared. RESULTS: Data linkage decreased the proportion of notifications with unknown Indigenous status by 74% from 10.2% to 2.7%. There was no significant difference in disease-specific age-adjusted notification rate ratio estimates based on pre-linkage data and post-linkage data for Aboriginal people compared with non-Aboriginal people. CONCLUSION: Our findings suggest that reported STI and BBV disease-specific age-adjusted notification rates for 2010 in Western Australia are unlikely to be significantly biased by excluding notifications with unknown Indigenous status. This finding is likely to be dependent on recent improvements in the reporting of Indigenous status in notification data in Western Australia. Cost-effective and systematic solutions, including the better use of existing data linkage resources, are required to facilitate continued improvement in the completeness of reporting and accuracy of estimates for notifiable STIs and BBVs in Australia by Aboriginality.