An Evaluation of the Current Type 2 Diabetes Guidelines: Where They Converge and Diverge

The ADA, WHO, and IHS guidelines recommend that adults be evaluated for type 2 diabetes if they are overweight (BMI ≥ 25 kg/m²) and have one or more of the following risk factors: first-degree relative with diabetes, women who delivered a baby weighing > 9 lb, diagnosis of hypertension > 140/90 mmHg, diagnosis of polycystic ovarian syndrome, history of gestational diabetes mellitus (GDM), or acanthosis nigricans (Table 1).^1,2,4  However, several minor differences do exist among the guidelines. The ADA¹  recommends that adults with prediabetes be screened annually and that adults who are ≥ 45 years of age without preexisting conditions be screened every 3 years. The WHO²  recommends that adults with a history of vascular disease be screened for diabetes every 3 years.

In comparison, the AACE guideline³  recommends that adults be assessed for diabetes if they have any of the following criteria: findings of impaired glucose tolerance (IGT) or impaired fasting glucose (IFG) from previous testing, a history of cardiovascular disease (CVD), high-risk ethnicity (non-white ancestry), physical inactivity, or are on antipsychotic therapy for schizophrenia or severe bipolar disease (Table 1). The main difference between the AACE guidelines and those of the other three organizations is that AACE does not include a BMI > 25 kg/m² in adults as a risk factor indicating the need for diabetes screening. Only the AACE guideline recommends that adults who are taking antipsychotic medications be screened for diabetes.³ 

Compared to the other four sets of guidelines, CMS recommendations carry more restrictive criteria for recommending diabetes screening because this guideline targets reimbursement for the Medicaid and Medicare patient populations. Under the CMS guidelines, diabetes screening is a covered benefit for individuals who have been diagnosed with hypertension, hyperlipidemia, IGT, or IFG or who are obese (BMI ≥ 30 kg/m²).⁵  Screening is also a covered benefit for individuals with at least two of the following risk factors: age ≥ 65 years, overweight (BMI > 25 but < 30 kg/m²), family history of diabetes, history of GDM, or delivery of an infant weighing > 9 lb.⁵ 

The five sets of guidelines compared^1–5  are largely in accord with each other in terms of diagnosis criteria for type 2 diabetes. For nonpregnant adults, diagnosis is based on either a fasting plasma glucose (FPG) level ≥ 126 mg/dl or a 2-hour plasma glucose level ≥ 200 mg/dl in an oral glucose tolerance test (OGTT) using a 75-g glucose load (Table 2). These tests should be repeated in the absence of unequivocal hyperglycemia.

One major difference among these guidelines is that ADA, AACE, and IHS guidelines include an A1C ≥ 6.5% as a diagnostic criterion for type 2 diabetes, whereas WHO and CMS guidelines do not.^1–5  Also, only the WHO guidelines include patients with a random plasma glucose ≥ 200 mg/dl and classic symptoms of hyperglycemia or hyperglycemic crisis as a diagnostic criterion for type 2 diabetes.² 

Patients with type 2 diabetes require long-term management plans. All five sets of guidelines are in agreement that patients can benefit from medical nutrition therapy and diabetes self-management education (Table 3).^1–5  Type 2 diabetes is a lifelong disease requiring patients to have advanced management skills. Diabetes education has proven to be a beneficial tool to aid patients in achieving their management goals; it helps improve patients' knowledge, which in turn may help to improve glycemic control, long-term diabetes management, and weight management.⁶ 

For medical management, only the ADA guidelines specifically recommend initiating metformin therapy at the time of diagnosis for patients in whom it is not contraindicated.¹  The AACE guidelines recommend several medications that can lower FPG and postprandial glucose, but it does not prioritize which medication should be initiated first at the time of diagnosis.³  Metformin often is the medication of choice for patients newly diagnosed with type 2 diabetes; it helps to decrease glucose production in the liver, increases the body's sensitivity to insulin, and does not cause weight gain.¹  However, depending on patient-specific factors, starting on an oral agent from a different drug class, such as a sulfonylurea, may be appropriate for patients with elevated FPG.³ 

In addition to starting glucose-lowering medications that affect glucose metabolism, the ADA, WHO, AACE, and IHS guidelines also recommend initiating aspirin therapy.^1–4  Patients with increased cardiovascular risk are strongly encouraged to begin an aspirin regimen to lower their risk.¹  Patients who have several risk factors for CVD, such as smoking, hypertension, hyperlipidemia, and age > 50 years for men or > 60 years for women, should begin taking low-dose aspirin.⁷  The ADA, AACE, and IHS guidelines also recommend that patients begin taking a statin regardless of their baseline lipid levels unless contraindicated.^1,3,4  Clinical judgment should be used when considering starting patients with either of these medications.

For a target glycemic goal, the ADA, WHO, and IHS guidelines recommend an A1C < 7%.^1,2,4  The AACE guidelines recommend an A1C ≤ 6.5%.³  Some individual patients such as those with a longer life expectancy, few comorbid conditions, and little to no history of hypoglycemia may benefit from stricter A1C goals, whereas others such as many elderly patients would benefit from a less stringent A1C goal. Physicians should incorporate these factors when determining the most appropriate individualized A1C goal for their patients. A comparison of the blood glucose, blood pressure, and lipid targets recommended in the ADA, WHO, AACE, and IHS guidelines is provided in Table 4.^1–4  CMS did not provide specific target goals for these categories.

Diabetes is associated with several micro- and macrovascular complications. Current recommendations are to monitor serum creatinine and urine albumin annually for early detection of diabetic nephropathy.^1–4  Annual eye exams are recommended for early detection of diabetic retinopathy.^1–4  Furthermore, the ADA, AACE, and IHS guidelines recommend that patients inspect their feet daily and have an annual comprehensive foot exam.^1,3,4  This exam should consist of a complete foot inspection, including assessment of foot structure, skin integrity, vascular status, and pedal pulses; testing for loss of sensation using a 10-g monofilament, and any one of the following tests: vibration sensation using a 128-Hz tuning fork, ankle reflexes, pinprick sensation, or vibration perception threshold.^1,4  However, only the ADA and IHS guidelines recommend screening for distal symmetric polyneuropathy at diagnosis and screening annually for diabetes neuropathy.^1,4 

In patients with chronic diseases, immunizations should be kept up to date to minimize the risk for complicating infections. The ADA and IHS guidelines recommend that patients living with diabetes have an annual influenza vaccine. The pneumococcal vaccine and the hepatitis B vaccination series are also recommended.^1,4  These recommendations overlap with current recommendations from the Centers of Disease Control and Prevention (CDC).⁸  In addition, the CDC and IHS recommend that patients living with diabetes be immunized with Zoster and tetanus/diphtheria vaccines.^4,8 

When screening for type 2 diabetes, some patients may be identified as having early signs of the disease but not meeting the criteria for diagnosis. At this stage, patients may be considered to have prediabetes. Often, they have IGT (2-hour OGTT values between 140 and 199 mg/dl), IFG (FPG between 100 and 126 mg/dl), or an A1C of 5.7–6.4%.¹ 

To prevent people with prediabetes from progressing to type 2 diabetes, the ADA, WHO, AACE, and IHS guidelines suggest lifestyle interventions such as physical activity for at least 150 minutes/week and smoking cessation.^1–4  Three of these four sets of guidelines (all but the IHS guidelines) recommend weight loss of at least 5–10% of body weight (Table 5). The CMS guidelines do not provide specific recommendations for the prevention of type 2 diabetes. In the Diabetes Prevention Program (DPP) study, lifestyle intervention with a goal of at least 7% weight loss along with physical activity of at least 150 minutes/week reduced the risk of developing type 2 diabetes.⁹  Participants in the lifestyle intervention group decreased their risk of developing type 2 diabetes by 58% compared to 31% in the metformin group. In a 10-year follow-up of the DPP, participants in the lifestyle intervention group maintained a 34% reduced risk of developing type 2 diabetes compared to 18% in the metformin group.¹⁰  The data from this study show that weight loss plays a significant role in decreasing patients' risk for developing type 2 diabetes.

ADA¹  and AACE³  recommend starting metformin when prediabetes is identified, but criteria for initiating this therapy differ between the two sets of guidelines. Details for the specific criteria outlined in each can be found in Table 5.

In terms of completeness, the ADA guidelines offer more suggested actions that HCPs could propose for their patients, including reducing their intake of sugar-sweetened beverages, reducing their total daily calories and dietary fat intake, and increasing their intake of dietary fiber through fruits and whole grains.¹ 

For well-studied chronic disease states, there are often several sets of recommendations providing guidance for HCPs. New research is constantly being published and leads to periodic revisions or updates to such guidelines. However, there will always be some similarities and some differences among different sets of guidelines. HCPs must note these similarities and differences and then rely on clinical judgment to provide the best possible care for patients. In choosing among the various practice guidelines for diabetes care, HCPs should consider the individualized needs of their patients based on each patient's medical history, comorbid conditions, age, and other factors. Above all, the patients must be the focal point of the decision-making process to increase the likelihood of success.