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
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.
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.
Sponsors
The Canadian Task Force on Preventive Health
Care developed this guideline with funding from Health Canada.
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.