Canadian Task Force updates diabetes screening guidelines

By Sally Robertson, B.Sc.Oct 19 2012

The Canadian Task Force on Preventive Health Care has updated its recommendations on screening asymptomatic adults for Type 2 diabetes.

The new guidelines highlight the lack of evidence to support the routine blood screening of adults at a low or moderate risk for diabetes who are less than 40 years of age.

Such screening appears to only be beneficial to adults of any age who are at a very high risk for the condition, while there is limited potential value in screening adults aged 40 years or older more than every 3-5 years.

"Screening may lead to overdiagnosis, inappropriate investigation and treatment, avoidable adverse effects, and unnecessary psychosocial and economic costs," say the guidelines, which are published in the Canadian Medical Association Journal.

The recommendations, which have been graded according to the Grading of Recommendations Assessment, Development and Evaluation (GRADE) system, draw attention to the fact that there is no evidence that screening for Type 2 diabetes in adults at low to moderate risk who are under 40 years of age actually reduces the incidence, mortality, or complications of diabetes. For these individuals, the task force says routine screening is therefore not recommended.

The task force now encourages a two-stage screening system, starting with the use of a validated risk calculator which can be used to identify people at high or very high risk, select patients for screening, and also inform them about their risk factors.

For adults of any age who are identified as being at very high risk for diabetes using a risk calculator, the guidelines recommend routine annual screening of glycated hemoglobin (HbA1c) levels.

For those with a low to moderate risk for the condition who are 40 years or older and for adults of any age who are at high risk, routine HbA1c screening every 3-5 years is advised.

However, the guidelines explain that GRADE offers two strengths of recommendations: strong and weak. "Strength of recommendation is based on the quality of the supporting evidence; the degree of uncertainty about the balance between desirable and undesirable effects; the degree of uncertainty or variability in values and preferences; and the degree of uncertainty about whether the intervention represents a wise use of resources."

Each of the new recommendations has been graded as weak, which implies that most people would want the recommended course of action but many would not.

The guidelines therefore emphasize that: "For clinicians, this means they must recognize that different choices will be appropriate for each person, and they must help each person arrive at a management decision consistent with his or her values and preferences."

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