Final Research Plan
Abnormal Blood Glucose and Type 2 Diabetes Mellitus: Screening
August 15, 2013
Recommendations made by the USPSTF are independent of the U.S. government. They should not be construed as an official position of the Agency for Healthcare Research and Quality or the U.S. Department of Health and Human Services.
The final Research Plan will be used to guide a systematic review of the evidence by researchers at an Evidence-based Practice Center. The resulting Evidence Report will form the basis of the USPSTF Recommendation Statement on this topic.
The draft Research Plan was available for comment from May 2 until May 29, 2013 at 5:00 p.m., ET.
Key Question 1 focuses on direct evidence on the effectiveness of screening for type 2 diabetes, impaired glucose tolerance, and impaired fasting glucose for improving future health outcomes compared with not screening or alternative screening strategies. Such direct evidence on the effectiveness of screening interventions may be limited. Therefore, the remainder of the Analytic Framework evaluates the chain of indirect evidence needed to link screening with improvement in important health outcomes. Links in the chain of indirect evidence include the effectiveness of screening and treatments in reducing the incidence of future health outcomes and the harms associated with screening and treatments. Implicit in the indirect chain of evidence is that to understand the benefits and harms of screening, it is not sufficient to identify individuals who have the disease; it is also necessary to show that there are effective treatments for those identified.
Note: The numbers correspond to the numbers of the Key Questions.
This Figure depicts the analytic framework, which outlines the evidence areas covered in the review, including the population, screening, interventions, intermediate and clinical health outcomes, and harms on a visual pathway. On the left side of the framework, the population includes nonpregnant adults who are asymptomatic for type 2 diabetes, impaired fasting glucose, or impaired glucose tolerance and screened in settings generalizable to primary care. An overarching arrow connects screening to clinical health outcomes on the far right side of the framework, specifically mortality, cardiovascular morbidity (including myocardial infarction, stroke, and congestive heart failure), chronic kidney disease, amputations, skin ulcers, visual impairment (including blindness), periodontitis (including tooth loss), moderate-severe neuropathy, and quality of life; an offshoot arrow assesses harms of screening. There is an initial branch in the framework that splits patients into high-risk or average-risk groups; the framework further splits patients into diabetes and prediabetes (impaired fasting glucose and/or impaired glucose tolerance) groups. Arrows lead from each of these groups to clinical health outcomes. In addition, an arrow leads from the prediabetes group to the incidence of type 2 diabetes. Drug and/or lifestyle interventions are represented in the center of the framework, and offshoot arrows represent harms resulting from these interventions. A dotted line represents the association between type 2 diabetes and clinical health outcomes.
- Is there direct evidence that systematic screening (either targeted or universal) for type 2 diabetes, impaired fasting glucose, or impaired glucose tolerance among asymptomatic, nonpregnant adults improves health outcomes?
- What are the harms of screening nonpregnant adults for type 2 diabetes, impaired fasting glucose, or impaired glucose tolerance?
- Do interventions for screen-detected or mild type 2 diabetes, impaired fasting glucose, or impaired glucose tolerance provide an incremental benefit in health outcomes compared with no interventions or initiating interventions after clinical diagnosis?
- What are the harms of interventions for screen-detected or mild type 2 diabetes, impaired fasting glucose, or impaired glucose tolerance?
- Is there evidence that more stringent blood pressure control, lipid control, or lifestyle interventions (compared with traditional control) improves health outcomes in nonpregnant adults with type 2 diabetes, impaired fasting glucose, or impaired glucose tolerance?
- Do interventions for impaired fasting glucose or impaired glucose tolerance delay or prevent the progression to type 2 diabetes?
- Do the effects of screening or interventions for screen-detected or mild type 2 diabetes, impaired fasting glucose, or impaired glucose tolerance vary by subgroups, such as age, sex, or race/ethnicity?
Contextual questions are not systematically reviewed and are not shown in the Analytic Framework.
- What is the yield (incidence) of starting screening at different ages or rescreening at different intervals among nonpregnant adults with an initial normal fasting blood glucose, hemoglobin A1c, or glucose tolerance test?
- What is the utility of using formal risk calculators versus risk factors (e.g., family history, body mass index) in determining an individual's risk for developing diabetes?
- What is the utility of existing modeling studies of type 2 diabetes screening versus no screening in examining important health outcomes?
The Research Approach identifies the study characteristics and criteria that the Evidence-based Practice Center will use to search for publications and to determine whether identified studies should be included or excluded from the Evidence Report. Criteria are overarching as well as specific to each of the key questions (KQs).
| Category | Include | Exclude |
|---|---|---|
| Populations |
KQs 1, 2: Asymptomatic, nonpregnant adults KQs 3, 4: Asymptomatic, nonpregnant adults with screen-detected or mild type 2 diabetes (based on untreated hemoglobin A1c levels), impaired fasting glucose, or impaired glucose tolerance KQ 5: Asymptomatic, nonpregnant adults with screen-detected or mild type 2 diabetes (based on untreated hemoglobin A1c levels), impaired fasting glucose, or impaired glucose tolerance, and also abnormal blood pressure and/or lipid levels KQ 6: Asymptomatic, nonpregnant adults with impaired fasting glucose or impaired glucose tolerance KQ 7: All of the above |
KQs 1–7: Children, adolescents, pregnant women; individuals with symptomatic type 2 diabetes, impaired fasting glucose, or impaired glucose tolerance |
| Interventions |
KQs 1, 2: Screening (targeted or universal) for impaired fasting glucose, impaired glucose tolerance, or diabetes KQs 3, 4, 6: Any intervention for glycemic control; lifestyle modification KQ 5: Any intervention for more stringent blood pressure or lipid control or aspirin; more intensive lifestyle modification KQ 7: All of the above |
|
| Comparison |
KQ 1: No screening or alternative screening strategies KQs 3, 4: No intervention/usual care or interventions in individuals with advanced diabetes KQ 5: Conventional intervention KQ 6: No intervention KQ 7: All of the above |
|
| Outcomes |
KQs 1, 3, 5: Mortality, cardiovascular morbidity (including myocardial infarction, stroke, congestive heart failure), chronic kidney disease, amputations, skin ulcers, visual impairment (including blindness), periodontitis (including tooth loss), moderate-severe neuropathy, quality of life KQ 2: Labeling, anxiety, false-positive results KQ 4: Serious side effects from treatments, including death, heart attack, stroke, cancer, and hypoglycemic event requiring medical attention KQ 6: Development of type 2 diabetes KQ 7: All of the above |
|
| Settings | KQs 1–7: Applicable to primary care | |
| Study Designs |
KQs 1, 3, 5, 6: Randomized, controlled trials and controlled observational studies, systematic reviews KQ 2: Any KQ 4: Randomized, controlled trials and controlled observational studies; systematic reviews; and large longitudinal studies. Observational studies will be included if they have at least 1 year of followup, at least 1,000 participants for controlled studies, or at least 5,000 participants for uncontrolled studies KQ 7: All of the above |
The draft Research Plan was posted for public comment on the U.S. Preventive Services Task Force (USPSTF) Web site from May 2 to May 29, 2013. The USPSTF received comments requesting clarification on the inclusion and exclusion criteria, analytic framework, and key questions related to populations, interventions, outcomes, and study designs. Most suggestions were determined to be out of scope for the intended review, such as the suggestion to include children and pregnant women, who may be the subject of a future review. In addition, it was decided to not include intermediate outcomes, such as blood glucose control, because data are available on clinical health outcomes. The focus of the USPSTF is primary care; therefore, only studies with settings generalizable to primary care are included. The USPSTF clarified that the decision to only include large studies is intended for the key question on harms of treatment only and limited to observational studies. There is no sample size cutoff for randomized, controlled trials or any of the other key questions.