Can the prevalence of diagnosed diabetes be estimated from linked national health records? The validity of a method applied in New Zealand.

ABSTRACT

INTRODUCTION: With projected global increases in the prevalence of Type 2 diabetes, the health sector requires timely assessments of the prevalence of this disease to monitor trends, plan services, and measure the efficacy of prevention programmes. AIM: To assess the validity of a method to estimate the prevalence of diagnosed diabetes from linked national health records. METHODS: We measured the agreement between a diabetes diagnosis (using combined national lists of drug dispensing, outpatient attendance, laboratory tests (HbA1c) and hospital diagnoses) and a primary care diabetes diagnosis in a (PREDICT™) cohort of 53,911 adult New Zealanders. The completeness of the diagnosis of diabetes in the cohort was estimated using capture-recapture methods. RESULTS: The primary care cohort had a high prevalence of recorded diabetes (20.9%, 11,266/53,911), similar to our derived prevalence of 20.1%. Of the participants with a diagnosis of diabetes, 89% (10,182/11,266) had a similar derived diagnosis, indicating that only about one in 10 people with a primary care diagnosis had not been either admitted to hospital, seen at outpatient clinics, prescribed diabetes drugs or undertaken regular HbA1c tests. The capture-recapture prevalence of diagnosed diabetes in this cohort was 23.7% indicating that primary care diagnoses in the cohort were about 90% complete. DISCUSSION: A method for estimating the prevalence of diagnosed diabetes from national health data shows high-level agreement with primary care records. Linked health data can provide an efficient method for estimating the prevalence of diagnosed diabetes in regions where such records are individually linked.