Abstract:
Background
Lack of population based data is a critical problem in diabetes surveillance in New
Zealand. This thesis looks at the feasibility, strengths and weaknesses of linking
existing databases to create a regional diabetes register in the Waikato.
Methods
Completeness and validity of key databases and agreement between common data
items have been studied using the following audits and studies linking multiple data
sources:
• A pilot study in a rural town (Taumarunui), linking multiple data sources
including the secondary care based Waikato Regional Diabetes Service
(WRDS) database and the Get Checked data from primary care.
• A general practice based study in Hamilton, linking primary care data (diagnosis
codes, prescriptions, laboratory tests, Get Checked) with the WRDS database.
• Another general practice based study in Rotorua, a town with high Maori
population, linking primary care data with deprivation scores.
• Audits using WRDS data and Waikato DHB hospital systems to assess data
agreement.
• Retention of patients in the Get Checked programme was examined using
Waikato Primary Health’s data.
• Three retrospective studies linking the WRDS data with Waikato DHB hospital
systems and national mortality data, which looked at hospital admissions,
progression of renal disease and mortality.
The studies used several methods of data validation including comparison of datasets,
manual search of patient records, direct contact with patients and comparison of data
from external sources. Linked datasets were used to identify disparities in prevalence
of diabetes, access to diabetes care, diabetes complications and mortality.
Results
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• The coverage of the WRDS database was high (86%-91%), but newly
diagnosed patients and older patients not needing retinal screening are underrepresented.
Case identification using primary care systems was high, but the
coverage of the “Get Checked” programme (62%-80%) varied depending on
practice IT systems, data handling procedures and patient characteristics.
• The Rotorua study shows that diabetes prevalence rises with increasing
deprivation among Europeans, but not among Maori.
• Maori and Asian patients were less likely to access retinal screening in
Hamilton. Patients aged<40 years, those of Maori or Asian origin, and those
with Type 1 diabetes were less likely to be retained in the Get Checked
programme with regular checks. Almost all patients had barriers to diabetes
care in Taumarunui. Psychological barriers to diabetes care rank highly for all
subgroups of ethnicity, age, gender, duration of diabetes and insulin treatment.
• Outcomes analyses showed that compared with Europeans with diabetes,
Maori diabetes patients had a significantly higher risk of end-stage renal
disease (ESRD), renal admission and renal death (46-fold, seven-fold and fourfold
increases, respectively). Maori patients progressed at a significantly faster
rate from first hospital admission for chronic renal disease to ESRD. Maori were
more likely than Europeans to have diabetes reported on mortality coding. They
were also were more likely to die from cardiovascular disease, cancer and renal
disease [Hazard-ratios 2.31(1.6-3.3), 1.83(1.1-3), and 11.74(4.8-29)
respectively].
Discussion
The advantages and the difficulties of linking primary care and secondary care
databases to identifying diagnosed diabetes patients, the potential barriers to
implementation of a diabetes register and the critical factors for a successful system
are discussed. This research has demonstrated the potential of linking databases to
monitor diabetes care and outcomes, but implementation would need substantial policy
changes and financial backing.