HbA _1cand cardiovascular risk score identify people who may benefit from preventive interventions: A 7 year follow-up of a high-risk screening programme for diabetes in primary care (ADDITION), Denmark

Aims/hypothesis: The measurement of HbA _1c is suggested as a diagnostic test for diabetes. Screening for diabetes also identifies individuals with elevated cardiovascular risk but who are free of diabetes. This study aims to assess whether screening by HbA _1c or glucose measures alone, or in combination with a cardiovascular risk assessment, identifies people who may benefit from preventive interventions, i.e. people with screen detected diabetes and people belonging to groups with excess mortality, during a median follow-up of 7 years. Methods: A population-based, stepwise high-risk screening programme was performed in 193 family practices from 2001 to 2006. Individuals aged between 40 and 69 years (N=163,185) were sent a diabetes risk questionnaire. Of these, 20,916 people at risk of diabetes were stratified by glucose measures (normal glucose tolerance [NGT], impaired fasting glucose [IFG], impaired glucose tolerance [IGT] and diabetes), HbA _1c (<6%; 6.0-6.4%; or ≥6.5%) and cardiovascular risk (heart SCORE <5 or ≥5). People were followed for a median of 7 years or until death. Excess mortality was calculated using the Cox hazard ratio (HR). Results: SCORE≥5 identified 91.7% (95% CI 91.1-92.3%) of those who might benefit from preventive interventions. SCORE≥5 in combination with HbA _1c≥6.0% identified 96.7% (95% CI 96.3-97.0%), compared with 97.6% (95% CI 97.2-97.9%) in combination with glucose measures. Glucose measures or HbA _1c alone identified 26.1% (95% CI 25.2-27.0%) and 19.8% (95% CI 19.0-20.6%), respectively. Conclusion/ interpretation: In a population-based high risk screening programme in primary care, HbA _1c≥6.0% combined with an elevated cardiovascular risk assessment (SCORE≥5) can feasibly be used to identify those who may benefit from preventive lifestyle intervention and/or polypharmacy. Trial registration: ClinicalTrials.gov NCT 00237549. Funding: The study received unrestricted grants from Novo Nordisk, Novo Nordisk Scandinavia, Astra Denmark, Pfizer Denmark, GlaxoSmithKline Pharma Denmark, Servier Denmark and HemoCue Denmark.