A new study shows that the screening of people ‘at-risk’ of developing type 2 diabetes may not be foolproof. Although subsequent lifestyle and/or drug interventions are relatively effective in preventing individual progression to diabetes, more research and resources need to be directed at the accurate detection of pre-diabetics.
The prevalence of diabetes is on the rise, and the number of people expected to die from its complications is projected to double from 2005 to 2030. One of the strategies adopted in trying to stop the disease in its track is the screen and treat approach: identify the subpopulation at a high risk of developing diabetes, and starting lifestyle/pharmacological intervention early to stop progression to full-on disease. Traditionally, one of two approaches is used to diagnose pre-diabetics: a) oral glucose tolerance test, where the subject is fasted overnight and fasting blood glucose levels measured the following day, and b) measurement of glycated hemoglobin in the blood (HbA1C), which reflects blood glucose concentrations over a two to three month period. People identified as pre-diabetic are next subjected to lifestyle or drug (often metformin) intervention.
A systematic review published in The BMJ showed that this screen and treat approach alone is unlikely to have a substantial impact on the worsening epidemic of type 2 diabetes. The review involved 49 studies of screening tests and 50 intervention trials, published in the biomedical databases Medline, PreMedline, and Embase. The study found that the diagnostic accuracy of tests was low: HbA1C is neither sensitive nor specific, while the fasting blood glucose test was specific but not sensitive. Hence, such tests may inaccurately diagnose a person as a pre-diabetic, or could falsely reassure individuals who are at-risk of developing the disease. The lack of a lifestyle/drug intervention in the latter group may result in an eventual progression to diabetes. The study also points out the international inconsistency in the diagnosis of pre-diabetics. For example, in the US, the American Diabetes Association recommends a fasting blood glucose concentration of 5.6-6.9 mmol/L or HbA1C of 39-47 mmol/mol, in order to qualify as a pre-diabetic. The World Health Organization (WHO), on the other hand, recommends a fasting blood glucose cut-off of 6.0-6.9 mmol/L and HbA1C of 42-47 mmol/mol.
The study further revealed that both lifestyle interventions and drug (metformin) treatment have some efficacy in preventing or delaying the onset of type 2 diabetes, although the protective effect of lifestyle changes is greatest in long-term interventions of three to six years. Furthermore, in women with a history of gestational diabetes, lifestyle intervention may not prevent the development of type 2 diabetes. In fact, they have the highest rates of progression to diabetes, with a 70% cumulative incidence of the disease after 10 years.
Results from this meta-analysis suggest that a screen and treat approach might not be very effective in preventing the rampant epidemic of diabetes. A more efficient approach may be achieved by population-wide strategies, including but not limited to, preserving green spaces, improving on the walkability of the environment, accurate and effective food labeling and regulation on food advertising, affordability in purchasing healthy foods such as fruit and vegetables, and implementation of healthy practices in schools.
Written By: Debapriya Dutta, PhD