Electronic Medical Record (EMR) data are an efficient method for constructing large type 1 diabetes (T1D) cohorts but are limited by availability of accurate diagnosis codes. We sought to derive an algorithm for identifying T1D using Electronic Medical Records - Primary Care (EMRPC) also known as EMRALD, a database including records from >300,000 primary care patients in Ontario, Canada. A 25% random sample of adults with diabetes and at least 1 year of records in EMRPC prior to September 30, 2015 formed the reference cohort. Charts of potential T1D cases (those on insulin±metformin) were abstracted; all others were classified as non-T1D. Algorithms were derived using variables from free-text searches (diagnosis terms in the Cumulative Patient Profile (CPP)) and standardized fields (medications, age, BMI) using 1)a priori combinations of variables; 2)classification and regression tree analysis (CART). Algorithms were evaluated for sensitivity, specificity, positive and negative predictive values (PPV and NPV) with adjustment for optimism for CART. Of 21,547 eligible patients with diabetes, the reference cohort was 5407: 4968 non-abstracted non-T1D, 240 abstracted non-T1D and 199 T1D. The prevalence of T1D was 3.7%. The optimal algorithm using a priori variable combinations was T1D diagnosis in the CPP + rapid-acting insulin (sensitivity 69.3% (95% CI 62.4-75.7%), specificity 99.8% (99.6-99.9), PPV 92.6% (87.2-96.3), NPV 98.8% (98.5-99.1)). CART partitioned on T1D diagnosis in the CPP, any insulin, and non-metformin oral hypoglycemic medications and improved performance with optimism-adjusted sensitivity of 77% (72.0-83.9), specificity 99.8% (99.8-100.0), PPV 96.8% (94.6-99.6), and NPV 99.1% (98.9-99.4). Simple algorithms using EMR variables yielded good diagnostic performance for identification of T1D and CART further improved performance. Pending additional validation these algorithms can be applied to study large T1D cohorts in EMR databases.


A. Weisman: None. J. Young: None. M. Kumar: None. P. Austin: None. K. Tu: None. L. Jaakkimainen: None. L. Lipscombe: None. G. Booth: None.


Diabetes Action Canada

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