CTF Structured Abstract: Screening for diabetes mellitus

Canadian Task Force on Preventive Health Care

Structured Abstract

Screening for Diabetes Mellitus in the Non-Pregnant Adult

Adapted by Marie-Dominique Beaulieu, MD, MSc, FCFP, Associate Professor, University of Montreal, Quebec, from materials prepared for the U.S. Preventive Services Task Force

These recommendations were finalized by the Task Force in January 1994

Objective
Burden of Suffering
Options
Outcomes

Evidence
Values
Benefits, Harms, and Costs
Recommendations

Validation
Sponsors
Selected References

Objective

To make recommendations about screening for type II (non-insulin dependent) diabetes mellitus (DM) in asymptomatic, non-pregnant adults in Canada.

Burden of Suffering

The prevalence of DM in the general Canadian population is estimated to vary between 2% and 2.7%, with prevalence rates increasing with age, and varying by race (prevalence is higher in Native Canadian populations). Other risk factors for diabetes include family history, obesity, impaired glucose tolerance, and a previous history of gestational diabetes. Diabetes may cause life threatening metabolic complications and is an important risk factor for other leading causes of death such as coronary heart disease, congestive heart failure and cerebrovascular disease. Most of this burden of illness is due to type II, or non-insulin dependent DM (NIDDM), which comprises approximately 80-90% of all cases. Type II diabetes generally occurs after age 30. Type I, or insulin dependent DM (IDDM), generally begins before this age.

Options

Primary option was whether or not to screen. Main screening tests were fasting plasma glucose and glycosylated proteins (HA1c, serum fructosamine). Random and 2-hour postprandial glucose screening tests were mentioned but not discussed.

Outcomes

Effectiveness of early treatment was indicated for microvascular complications (diabetic nephropathy and retinopathy), macrovascular complications (e.g., cardiovascular, cerebrovascular and peripheral vascular events), and development of DM. Test properties included sensitivity and specificity.

Evidence

These recommendations were adapted from materials prepared for the 1989 U.S. Preventive Services Task Force (USPSTF). MEDLINE was searched for English-language articles published from 1989 to 1993 using the keywords diabetes non-insulin-dependent or diabetes-gestational and diagnosis, epidemiology and prevention-control. Study results were synthesized in table or graphic format only.

Recommendations were graded as:

A Good evidence to support the recommendation that the condition be specifically considered in a PHE.

B Fair evidence to support the recommendation that the condition be specifically considered in a PHE.

C Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.

D Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

E Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

Quality of evidence was rated according to 5 levels:

I Evidence from at least 1 properly randomized controlled trial (RCT).

II-1 Evidence from well-designed controlled trials without randomization.

II-2 Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.

II-3 Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.

III Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.

Values

The 13-member Task Force of experts in family medicine, geriatric medicine, pediatrics, psychiatry and epidemiology used an evidence-based method for evaluating the effectiveness of preventive health care interventions. Recommendations were not based on cost-effectiveness of options. Patient preferences were not discussed.

Background papers providing critical appraisal of the evidence and tentative recommendations prepared by the chapter author were pre-circulated to the members. Evidence for this topic was presented and deliberated upon in 1- to 2-day meetings, 2 to 3 times per year from January 1993 to June 1993. Consensus was reached on final recommendations.

Benefits, Harms, and Costs

Reported sensitivities of fasting plasma glucose range from 21% to 73%, depending on the cut-off used to define a positive result, and the properties of the gold standard (fasting or random venous plasma glucose measurement or oral glucose tolerance test). Reported sensitivities and specificities of glycosylated proteins ranged from 15% to 91% and 84% to 89%, respectively. Potential harms of screening relate to false positive test results and labelling of individuals.

There is no conclusive evidence that screening and early treatment of asymptomatic persons, even those at high-risk, leads to improved outcomes. No published studies provide firm evidence that improved glycemic control reduces microvascular complications in patients with type II DM.

Disease duration and degree of glycemic control do not affect macrovascular complications. A review of a WHO multinational cohort study found no increased risk of cardiovascular events in patients with type II DM at 8 year follow-up.

Little direct evidence from cohort studies supports that asymptomatic persons benefit from screening for and treatment of impaired glucose tolerance (IGT), an intermediate form of disordered glucose metabolism that falls between normal glucose tolerance and a diabetic state. Most asymptomatic persons with untreated IGT do not develop diabetes.

Potential adverse effects of treatment relate to dietary restrictions, medications and risk of hypoglycemic events.

Recommendations

Recommendation grade [A, B, C, D, E] and level of evidence [I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations in support of individual recommendations are identified in the guideline text.

There is fair evidence to exclude (from the PHE) screening of asymptomatic, non-pregnant individuals for diabetes mellitus using fasting blood glucose levels [D, II-2]. Selective case-finding in high-risk groups (Native Canadians, Hispanic or Black Americans, the elderly, individuals who are obese, have a family history or gestational diabetes) may be prudent.

Validation

This report was externally peer reviewed. This recommendation is consistent with that of the USPSTF in 1989 and the American Diabetes Association.

Selected References

Source Document

Beaulieu MD. Screening for diabetes mellitus in the non-pregnant adult. In: Canadian Task Force on the Periodic Health Examination. Canadian Guide to Clinical Preventive Health Care. Ottawa: Health Canada, 1994; 602-9.

Link to Full Text of this review

Link to Summary Table of Recommendations of this review

Link to Selected References list of this review

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A	Good evidence to support the recommendation that the condition be specifically considered in a PHE.
B	Fair evidence to support the recommendation that the condition be specifically considered in a PHE.
C	Poor evidence regarding inclusion or exclusion of the condition in a PHE, but recommendations may be made on other grounds.
D	Fair evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.
E	Good evidence to support the recommendation that the condition be specifically excluded from consideration in a PHE.

I	Evidence from at least 1 properly randomized controlled trial (RCT).
II-1	Evidence from well-designed controlled trials without randomization.
II-2	Evidence from well-designed cohort or case-control analytic studies, preferably from more than 1 centre or research group.
II-3	Evidence from comparisons between times or places with or without the intervention. Dramatic results in uncontrolled experiments could also be included here.
III	Opinions of respected authorities, based on clinical experience, descriptive studies or reports of expert committees.