The US Preventive Services Task Force (USPSTF) grades its recommendations (A, B, C, D, or I) and identifies the Levels of Certainty regarding Net Benefit (High, Moderate, and Low). The definitions of these grades can be found at the end of the "Major Recommendations" field.
Summary of Recommendations and Evidence
The USPSTF recommends screening for type 2 diabetes in asymptomatic adults with sustained blood pressure (either treated or untreated) greater than 135/80 mm Hg. This is a grade B recommendation.
The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of routine screening for type 2 diabetes in asymptomatic adults with blood pressure of 135/80 mm Hg or lower. This is an I statement.
Clinical Considerations
Patient Population under Consideration
This recommendation concerns adults without symptoms of diabetes or evidence of possible diabetes complications. Symptoms of diabetes include polyuria, polydipsia, and polyphagia. Possible diabetes complications include nonhealing ulcers or infections and established vascular disease (for example, coronary artery disease, stroke, and peripheral artery disease). Persons with these symptoms or conditions should be tested for diabetes.
Suggestions for Practice Regarding the I Statement
In persons with blood pressure of 135/80 mm Hg or lower, screening may be considered on an individual basis if knowledge of diabetes status would help inform decisions about coronary heart disease (CHD) prevention strategies, including assessment of CHD risk and subsequent consideration of lipid-lowering agents or aspirin.
For example, consider a patient for whom lipid-lowering treatment would be recommended if his or her 10-year CHD risk was 20% or greater (see Risk Assessment, below). If the patient's calculated risk was 17% without diabetes and greater than 20% with diabetes, then screening for diabetes would be useful in determining lipid treatment. However, if the calculated risk was 10% without diabetes and 15% with diabetes, then the screening test result would have no effect on the decision whether to use lipid-lowering treatment.
Risk Assessment
Blood pressure is an important predictor of complications of cardiovascular disease (CVD) (including CHD and stroke) in persons with type 2 diabetes mellitus and should be measured as the first step in applying this recommendation. The examination of global CHD and stroke risk allows the clinician to determine how aggressive treatment for CVD risk factors needs to be. In making this assessment, clinicians should use any of several validated CHD risk assessment calculators, such as the calculator based on Framingham Heart Study data (available at www.intmed.mcw.edu/clincalc/heartrisk.html).
Screening Tests
Three tests have been used to screen for diabetes: fasting plasma glucose, 2-hour postload plasma glucose, and hemoglobin A1c. Each has advantages and disadvantages. The American Diabetes Association has recommended the fasting plasma glucose test for screening because it is easier and faster to perform, more convenient and acceptable to patients, and less expensive than other screening tests. The fasting plasma glucose test has more reproducible results than does the 2-hour postload plasma glucose test, has less intraindividual variation, and has similar predictive value for development of microvascular complications of diabetes. The American Diabetes Association defines diabetes as a fasting plasma glucose level of 126 mg/dL or greater and recommends confirmation with a repeated screening test on a separate day, especially for people with borderline results.
Treatment of Persons with Sustained Blood Pressure of 135/80 mm Hg or Greater
Blood pressure targets should be lower for persons who have type 2 diabetes mellitus than for those who do not. Lower blood pressure targets for persons with diabetes and high blood pressure reduce CVD events compared with higher targets. Attention to other risk factors for CVD, such as physical inactivity, lipid levels, diet, and obesity, is also important, both to decrease risk for CHD and to improve glucose control.
Screening Intervals
The optimal screening interval is not known. The American Diabetes Association, on the basis of expert opinion, recommends a 3-year interval.
Other Approaches to Prevention
There is no evidence of benefit in health outcomes from screening for impaired glucose tolerance (IGT) or impaired fasting glucose (IFG). However, intensive programs of lifestyle modification (diet, exercise, and behavior) do reduce the incidence of diabetes. Regardless of whether the clinician and patient decide to screen for diabetes, people should eat a healthful diet, be active, and maintain a healthy weight—these behaviors have other benefits in addition to preventing or forestalling type 2 diabetes. The USPSTF recommends intensive interventions for obese persons who desire to lose weight. Population-based approaches to increasing physical activity and reducing obesity, as recommended by the Task Force on Community Preventive Services, should be supported.
Useful Resources
Evidence and USPSTF recommendations on blood pressure, diet, physical activity, and obesity are available at www.preventiveservices.ahrq.gov. The reviews and recommendations for the Task Force on Community Preventive Services may be found at www.thecommunityguide.org.
Definitions:
What the United States Preventive Services Task Force (USPSTF) Grades Mean and Suggestions for Practice
| Grade |
Grade Definitions |
Suggestions for Practice |
| A |
The USPSTF recommends the service. There is high certainty that the net benefit is substantial. |
Offer or provide this service. |
| B |
The USPSTF recommends the service. There is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial. |
Offer or provide this service. |
| C |
The USPSTF recommends against routinely providing the service. There may be considerations that support providing the service in an individual patient. There is moderate or high certainty that the net benefit is small. |
Offer/provide this service only if there are other considerations in support of the offering/providing the service in an individual patient. |
| D |
The USPSTF recommends against the service. There is moderate or high certainty that the service has no net benefit or that the harms outweigh the benefits. |
Discourage the use of this service. |
I
Statement
|
The USPSTF concludes that the current evidence is insufficient to assess the balance of benefits and harms of the service. Evidence is lacking, of poor quality or conflicting, and the balance of benefits and harms cannot be determined. |
Read "Clinical Considerations" section of USPSTF Recommendation Statement (see "Major Recommendations" field). If offered, patients should understand the uncertainty about the balance of benefits and harms. |
USPSTF Levels of Certainty Regarding Net Benefit
Definition: The U.S. Preventive Services Task Force defines certainty as "likelihood that the USPSTF assessment of the net benefit of a preventive service is correct." The net benefit is defined as benefit minus harm of the preventive service as implemented in a general, primary care population. The USPSTF assigns a certainty level based on the nature of the overall evidence available to assess the net benefit of a preventive service.
| Level of Certainty |
Description |
| High |
The available evidence usually includes consistent results from well-designed, well-conducted studies in representative primary care populations. These studies assess the effects of the preventive service on health outcomes. This conclusion is therefore unlikely to be strongly affected by the results of future studies. |
| Moderate |
The available evidence is sufficient to determine the effects of the preventive service on health outcomes, but confidence in the estimate is constrained by factors such as:
- The number, size, or quality of individual studies
- Inconsistency of findings across individual studies
- Limited generalizability of findings to routine primary care practice
- Lack of coherence in the chain of evidence
As more information becomes available, the magnitude or direction of the observed effect could change, and this change may be large enough to alter the conclusion.
|
| Low |
The available evidence is insufficient to assess effects on health outcomes. Evidence is insufficient because of:
- The limited number or size of studies
- Important flaws in study design or methods
- Inconsistency of findings across individual studies
- Gaps in the chain of evidence
- Findings not generalizable to routine primary care practice
- A lack of information on important health outcomes
More information may allow an estimation of effects on health outcomes.
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