THE VALIDITY OF MAORI HOSPITAL DISCHARGE STATISTICS FOR ISCHEMIC-HEART-DISEASE IN NEW-ZEALAND

Data from an Auckland coronary heart disease register for the years 19 83 to 1991 have been used to assess the validity of routine national s tatistics on Maori hospital discharge rates for ischaemic heart diseas e. Ethnicity as recorded on the hospital admission record was compared with self defined ethnicity as recorded by register interviewers. Unl ike routine New Zealand mortality statistics, where there is marked un derreporting of Maori mortality, it appears that hospital discharge st atistics are not markedly affected by misclassification of ethnicity. Approximately 12% of those classified on the admission record as Maori considered themselves to be of a different ethnicity, and 0.5% of tho se classified as 'other' considered themselves to be Maori. Because of the small proportion of the population (and of ischaemic heart diseas e deaths) who are Maori, the two misclassifications cancel out and the overall routinely reported hospital morbidity rates are similar to ra tes based on self reported ethnicity. For example, in 1990, routine na tional statistics show that there were 345 Maori hospital discharges o r deaths due to ischaemic heart disease, and 8946 events among other e thnic groups. After adjustment using the register figures to reflect s elf defined ethnicity, the figures were 347 and 8944 respectively.