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Introduction: Cardiovascular disease (CVD) is the leading cause of death in New Zealand. As cholesterol is a major modifiable risk factor, national CVD guidelines recommend that adults have cholesterol levels monitored regularly (ranging from annually to at least 10 yearly). Aims This thesis aims to describe the spatial and socio-demographic distribution of lipid screening and monitoring among adults aged 30 years and above in the Auckland region, stratified by presence of prior CVD and key determinants including age, gender, ethnicity, deprivation and geographic location. This thesis focuses explicitly on the equity of lipid screening for those without CVD and lipid monitoring for those with CVD. Method: Using encrypted NHIs (eNHI) to anonymously link three nationally held datasets (Primary Health Organisation [PHO] enrolment data, laboratory claims data and hospital discharge data), a regional cohort was developed comprising the population aged 30 years and above enrolled in an Auckland PHO in the first quarter of 2011. No identifier information was available in this dataset although CVD, cholesterol testing (Total Cholesterol, HDL-cholesterol, TC:HDL ratio, LDL-cholesterol and Triglycerides) and demographic information was retained for the period of 2006-2010. Using STATA Version 10.0, the proportion of the population screened and monitored stratified by key determinants was used to measure equity. The extent of inequities within each analysis was estimated using the range and Extremal Quotient (ratio of highest to lowest value). Poisson regression analyses were conducted to estimate the likelihood of screening and monitoring, adjusting for all covariates. In addition, rates of cholesterol screening and monitoring (per 1,000 people) were calculated for each of the 399 Census Area Units in the Greater Auckland region and mapped using ArcGIS Version 10. Findings: This thesis included a total of 622,467 patients of which 55,707 (8.95%) had diagnosed CVD. The overall frequency of screening was 67.94% and the frequency of monitoring was 93.65%. From 2006 to 2010, the proportion of the population screened increased from 26.90% to 37.77% and from 60.81% to 67.96% for those with CVD. Among the population screened, women were 2% less likely than men to be screened (adjusted IRR 0.98; 95% CI 0.97 to 0.98), and when compared to people aged 55-64 years, those aged 35-54 years were 39% less likely to be screened (adjusted IRR 0.61; 95% CI 0.60 to 0.62). The likelihood of screening improved with increased age, up to age 79 years. People of Indian and Pacific ethnicity were 19% (adjusted IRR 1.19; 95% CI 1.18 to 1.21) and 5% (adjusted IRR 1.05; 95% CI 1.04 to 1.06) more likely than Europeans to be screened respectively. However, Māori and Europeans were equally likely to be tested. As Māori have a higher risk of CVD outcomes and an increased burden of disease, these findings are inequitable. There were no differences in screening by deprivation (NZDep Index). Spatial mapping revealed marked variation in cholesterol screening by neighbourhood. Among patients with diagnosed CVD, women were 3% less likely than men to be monitored (adjusted IRR 0.97; 95% CI 0.95 to 0.99), and when compared to people aged 55-64 years, those aged 30-34 years were 40% less likely to be monitored (adjusted IRR 0.60; 95% CI 0.52 to 0.68) and those aged 35-44 were 17% less likely to be monitored (adjusted IRR 0.83; 95% CI 0.79 to 0.87). The likelihood of screening improved with increasing age, up to age 79 years. People of Indian and Pacific ethnicity were 3% (adjusted IRR 1.03; 95% CI 0.99 to 1.07) and 2% (adjusted IRR 1.02; 95% CI 0.98 to 1.05) more likely than Europeans to be monitored respectively. Māori and Europeans were equally likely to be monitored and there were no differences in screening by deprivation (NZDep Index). Spatial mapping revealed marked variation in cholesterol monitoring by neighbourhood. Conclusion This thesis was the first in New Zealand to assess the equity of lipid screening and monitoring in the Auckland region and identified substantial differences in the spatial and socio-demographic distribution of lipid testing. This thesis found the certain population groups in this cohort were more likely to be screened or monitored than others and that inequities persisted throughout the five years. The observed inequities in screening for cholesterol require targeted intervention in front of line care delivery to achieve national performance targets for CVD risk assessment. In addition, those with CVD are extremely vulnerable in that they have a very high risk of subsequent CVD events or death. Key recommendations for reducing these inequities as a means of reducing the burden of CVD in New Zealand include: creating a better linkage between primary and hospital care, creating better patient reminder systems, investing in occupation-based risk factor monitoring and revising DHB population health targeted interventions for Māori. |
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