Hospital admission rates and emergency department use in relation to glycated hemoglobin in people with diabetes mellitus: a linkage study using electronic medical record and administrative data in Ontario.

BACKGROUND: The Canadian Primary Care Sentinel Surveillance Network (CPCSSN) collects extensive data on primary care patients but it currently does not gather reliable information on outcomes in other settings. The objectives of this study were to link electronic medical record (EMR) data from Ontario patients in the CPCSSN with administrative data from the Institute for Clinical Evaluative Sciences (ICES), to assess the representativeness of the CPCSSN population, and to identify people with diabetes in the CPCSSN data and describe their emergency department (ED) visits and hospital admissions over a 2-year period (2010-2012) by HbA1c level.

METHODS: We conducted a cross-sectional study linking 2014 Ontario CPCSSN data with ICES administrative data and a retrospective cohort study using the 2014 data extraction linked with data from the Ontario health care registry, hospital discharge abstracts and a database of emergency department visits. Demographics of CPCSSN patients were compared with those of the Ontario population. Patients with a CPCSSN diagnosis of diabetes were compared by HbA1c category for ED visits, hospital admissions and diagnosis of diabetes-related complications.

RESULTS: The linkage rate was 99%. We identified 12 358 patients with diabetes, 2356 of whom were missing data on HbAIc, for a final sample of 10 002. Patients with diabetes had a mean age of 64 years. Those with a higher HbA1c were younger, more likely to be male, had a lower income, had more comorbidities and were more likely to live in rural or suburban areas than patients with a lower HbA1c. Over the study period 31.8% of patients had 1 or more ED visits and 13.7% had a hospital admission for a diabetes-related complication. Patients with HbA1c greater than 8 had significantly more hospital admissions, ED visits and diabetes-related complications than patients with a lower HbA1c .

INTERPRETATION: The linkage between EMR and administrative data was successful. In this study population, higher HbA1c values were associated with increased ED visits and hospital admissions, with an increasing gradient as HbA1c increased from less than 7% to greater than 8%.