‘Screen and treat’ unlikely to halt diabetes epidemic
medwireNews: Screening measures for prediabetes do not accurately identify people at risk for developing diabetes, so preventive interventions will have only a small impact, say the authors of a meta-analysis published in The BMJ.
Eleanor Barry (University of Oxford, UK) and colleagues reviewed 49 screening studies. They found that the thresholds used for defining prediabetes varied between studies, but the overall sensitivity of glycated hemoglobin (HbA1c) for detecting future diabetes risk was just 49%, and average specificity was 79%.
The average sensitivity of fasting glucose was even lower, at 25%, although specificity was higher, at 94%.
This means that “many people will receive an incorrect diagnosis and be referred on for interventions while others will be falsely reassured and not offered the intervention,” they write.
The team also found that these measures tended to identify different groups of people. For example, using criteria from the World Health Organization guidelines, 48% of people with elevated HbA1c had normal fasting plasma glucose and 2-hour fasting glucose.
Editorialist Norman Waugh (University of Warwick, Coventry, UK) observes: “Given the imperfections of HbA1c and fasting plasma glucose, it is a pity that more research has not been done on the non-fasting 50 g glucose challenge test, much used in screening for gestational diabetes but rarely used in screening for type 2 diabetes or impaired glucose tolerance.”
He notes previous research suggesting that this test could offer an accurate screening tool.
Meta-analysis of 25 intervention trials showed that lifestyle interventions lasting between 6 months and 2 years reduced participants’ risk for developing diabetes by 31%, and those lasting between 3 and 6 years produced a 37% relative risk reduction. Only a few studies followed up patients for a period after the intervention phase; these revealed a sustained but smaller protective effect against diabetes, of 20%.
Treatment with metformin in four studies led to an overall 26% reduction in diabetes risk, but no study continued to monitor patients after they had stopped taking the drug.
Discussing the impact of interventions, Waugh notes the previous finding from the EPIC–Norfolk population cohort showing that two-thirds of diabetes cases occur in people who have baseline HbA1c levels below 6.0%, implying that preventive measures targeting people with prediabetes are only capturing a minority of people at risk.
Therefore, tackling the diabetes epidemic requires measures targeted at the entire population, he says, which “could include interventions to help weight control such as changes to taxation of foodstuffs, for example, making diet versions of soft drinks cheaper than sugary versions, and interventions to make physical activity easier or safer such as cycle lanes separate from traffic.”
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