Screening for Type 2 Diabetes Mellitus in Adults

Case Study

KC, a 46-year-old woman, visits your office to refill her cholesterol-lowering medication. She says she saw a recent news feature on the "diabetes epidemic" and asks if she needs to be tested. To better counsel her, you consult the U.S. Preventive Services Task Force (USPSTF) recommendations on screening for type 2 diabetes mellitus.

Case Study Questions

Question

1. Which one of the following screening options for KC is most consistent with the USPSTF recommendation on screening for type 2 diabetes mellitus

A. Screen for type 2 diabetes because she has hyperlipidemia.

B. Screen for type 2 diabetes because she is over 45 years of age.

C. Do not screen for type 2 diabetes until she becomes symptomatic.

D. Do not screen for type 2 diabetes until she is 65.

E. Screen for type 2 diabetes because she is a woman.

2. Which of the following statements about diabetes screening and glycemic control is/are correct?

A. Diabetes screening and early glucose control has been shown to improve health outcomes compared with initiating treatment after clinical diagnosis.

B. Intensive glycemic control in patients with clinically detected diabetes can reduce the progression of microvascular disease.

C. Existing studies have not shown that tight glycemic control significantly reduces myocardial infarction and stroke.

D. Available screening tests can accurately detect type 2 diabetes during an early, asymptomatic phase.

3. Which of the following statements about adults with diabetes and hypertension and/or hyperlipidemia is/are correct?

A. Persons with diabetes and hypertension benefit from a blood pressure level lower than conventional target levels.

B. Persons with diabetes and hyperlipidemia benefit from cholesterol levels lower than conventional target levels.

C. Diabetes is not a cardiovascular risk factor.

D. Improving activity level, diet, and weight can improve glycemic control but does not reduce the risk of heart disease.

Answers

1. The correct answer is A. The USPSTF recommends screening for type 2 diabetes in adults with hyperlipidemia or hypertension as part of an integrated approach to cardiovascular risk reduction. Patients at increased risk for cardiovascular disease may benefit most from screening for type 2 diabetes, because management of cardiovascular risk factors reduces major cardiovascular events. In the absence of evidence that routine screening produces direct benefits, the decision whether to screen individual patients for type 2 diabetes is a matter of clinical judgment. Regardless of whether the clinician and patient decide to screen for diabetes, patients should be encouraged to develop or maintain healthy lifestyle behaviors to reduce cardiovascular risk and risk for developing diabetes. Clinicians should be alert to symptoms of diabetes and test anyone with those symptoms.

2. The correct answers are B, C, and D. The USPSTF found good evidence that screening tests can accurately detect type 2 diabetes during an early, asymptomatic phase and good evidence that intensive glycemic control in patients with clinically detected (not screening detected) diabetes can reduce the progression of microvascular disease. However, it has not been demonstrated that beginning diabetes control early as a result of screening provides an incremental benefit compared with starting treatment after clinical diagnosis. Studies have not shown that tight glycemic control significantly reduces macro-vascular complications, including myocardial infarction and stroke. The USPSTF also found poor evidence to assess possible harms of screening. As a result, the USPSTF could not determine the balance of benefits and harms of routinely screening all adults for diabetes.

3. The correct answers are A and B. Persons with diabetes and hypertension benefit from lower blood pressure levels, and persons with diabetes and hyperlipidemia benefit from lower cholesterol levels. An elevated blood glucose level is an independent risk factor for cardiovascular disease, and risk increases with glucose level. The USPSTF found good evidence that, in adults with hypertension and clinically detected diabetes, lowering blood pressure below conventional target blood pressure (i.e., diastolic blood pressure ≤80 mm Hg) reduces the incidence of cardiovascular events and cardiovascular mortality. Among patients with hyperlipidemia, there is good evidence that detecting diabetes substantially im-proves individual coronary heart disease risk estimation, an integral part of lipid-lowering therapy decisions. Expert guidelines, such as the report of the Adult Treatment Panel III of the National Cho-lesterol Education Pro-gram, recommend lower low-density lipoprotein cholesterol levels for patients with diabetes than conventional target levels. Improving activity level, diet, and weight can improve glycemic control and help reduce the risk for heart disease.

KENNETH FINK, M.D., M.G.A., M.P.H.
Program Director
U.S. Preventive Services Task Force
Center for Primary Care, Prevention, and Clinical Partnerships
Agency for Healthcare Research and Quality

BARBARA CLARK, M.S.N., M.P.H.

SOURCES

U.S. Preventive Services Task Force. Screening for type 2 diabetes mellitus in adults: recommendations and rationale. Accessed November, 2003 at: http://www.ahrq. gov/clinic/3rduspstf/diabscr/diabetrr.htm.

Harris R, Donahue K, Rathore S, Frame P, Woolf S, Lohr KN. Screening adults for type 2 diabetes: a review of the evidence for the U.S. Preventive Services Task Force. Ann Intern Med 2003;138:215-90.

Harris R, Lux L, Bunton A, et al. Screening for type 2 diabetes mellitus: systematic evidence review no. 19.(Prepared by Research Triangle Institute - University of North Carolina Evidence-based Practice Center under Contract No. 290-97-0017). Accessed November, 2003 at: http://www.ahrq.gov/clinic/serfiles.htm.

The case study and answers to the following questions on screening for type 2 diabetes in adults are based on the recommendations of the U.S. Preventive Services Task Force (USPSTF), part of the Put Prevention into Practice program of the Agency for Healthcare Research and Quality (AHRQ). This recommendation was released in 2002 and is an update of the 1996 recommendation on screening for type 2 diabetes in adults. More detailed information on this subject is available in the USPSTF Recom-mendations and Rationale, the summary of the evidence, and the systematic evidence review on the USPSTF Web site (http://www.ahrq.gov/clinic/uspstfix.htm). The summary of the evidence and recommendation statement are available in print by subscription through the AHRQ Publi-cations Clearinghouse (800-358-9295, e-mail, ahrqpubs@ahrq.gov).

This case study is part of AFP's CME. See "Clinical Quiz" on page 477.

This clinical content conforms to AAFP criteria for evidence-based continuing medical education (EB CME). EB CME is clinical content presented with practice recommendations supported by evidence that has been systematically reviewed by an AAFP-approved source. The practice recommendations in this activity are available at http://www.ahrq.gov/clinic/uspstf/ uspsdiab.htm.