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Practice guideline: Glycosylated hemoglobin (A1C) monitoring in patients with DM every 6 months, with a goal A1C < 7 %

Prospective randomized clinical trials such as the Diabetes Control and Complications Trial (DCCT) and the U.K. Prospective Diabetes Study (UKPDS) have shown that improved glycemic control is associated with sustained decreased rates of retinopathy, nephropathy, and neuropathy. In these trials, treatment regimens that reduced average A1C to 7% (1% above the upper limits of normal) were associated with fewer long-term microvascular complications; however, intensive control was found to increase the risk of severe hypoglycemia and weight gain. Epidemiological studies support the potential of intensive glycemic control in the reduction of CVD.

A1C testing should be performed routinely in all patients with diabetes, first to document the degree of glycemic control at initial assessment and then as part of continuing care. Since the A1C test reflects mean glycemia over the preceding 2–3 months, measurement approximately every 3 months is required to determine whether a patient’s metabolic control has been reached and maintained within the target range. An A1c of 7% correlates to a mean plasma glucose value of approximately 170 mg/dl [i]. For any individual patient, the frequency of A1C testing should be dependent on the clinical situation, the treatment regimen used, and the judgment of the clinician. The A1C test should be performed at least two times a year in patients who are meeting treatment goals (and who have stable glycemic control) and quarterly in patients whose therapy has changed or who are not meeting glycemic goals.

Additional resource: Standards of Medical Care for Patients With Diabetes Mellitus (pdf) [i]

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Practice guideline: Blood pressure monitoring in patients with DM every six months, with a goal BP < 130/80 mmHG

The UKPDS (U.K. Prospective Diabetes Study) and the Hypertension Optimal Treatment (HOT) trials both demonstrated improved outcomes, especially in preventing stroke, in patients assigned to lower blood pressure targets. In the UKPDS epidemiological study, each 10-mmHg decrease in mean systolic blood pressure was associated with reductions in risk of 12% for any complication related to diabetes, 15% for deaths related to diabetes, 11% for myocardial infarction, and 13% for microvascular complications. Optimal outcomes in the HOT study were achieved in the group with a target diastolic blood pressure of 80 mmHg (achieved 82.6 mmHg). Randomized clinical trials demonstrate the benefit of targeting a diastolic blood pressure of<![endif]> less than or equal to 80 mmHg. Epidemiological analyses show that blood pressures greater than or equal to 120/70 mmHg are associated with increased cardiovascular event rates and mortality in persons with diabetes. Therefore, a target blood pressure goal of <130/80 mmHg is reasonable if it can be safely achieved.

Practice guideline: ACE inhibitor or ARB for diabetic patients with hypertension

Many studies have shown that in hypertensive patients with type 1 diabetes, ACE inhibitors can reduce the level of albuminuria and the rate of progression of renal disease to a greater degree than other antihypertensive agents that lower blood pressure by an equal amount. Other studies have shown that there is benefit in reducing the progression of microalbuminuria in normotensive patients with type 1 diabetes and normotensive and hypertensive patients with type 2 diabetes.

Additional resources: Treatment of Hypertension in Adults With Diabetes [ii]
Preserving Renal Function in Adults With Hypertension and Diabetes: A Consensus Approach [iii] (MD Consult login required)

Practice guideline: LDL-cholesterol, HDL-cholesterol, and triglyceride measurements annually in patients with DM, with LDL-C < 100 mg/dl, HDL-C> 45 mg/dl, and triglycerides <150 mg/dl

A number of secondary CHD prevention trials have included small numbers of adult type 2 diabetic subjects. In the Scandinavian Simvastatin Survival Study (4S) trial, simvastatin (HMG CoA reductase inhibitor or "statin") significantly reduced CHD incidence and total mortality (borderline significantly) in diabetic subjects with high LDL cholesterol and with previous clinical CHD. In the Cholesterol and Recurrent Events (CARE) study, pravastatin reduced CHD incidence significantly in diabetic subjects with average LDL levels and with previous clinical CHD. In the Helsinki Heart Study, gemfibrozil (fibric acid derivative) was associated with a reduction in CHD in diabetic subjects without prior CHD (although this result was not statistically significant). In the Veterans Affairs High-Density Lipoprotein Cholesterol Intervention Trial (VA-HIT), gemfibrozil was associated with a 24% decrease in cardiovascular events in diabetic subjects with prior cardiovascular disease.

The CARDS trial Collaborative Atorvastatin in Diabetes Study (The Lancet Aug 2004;9435:685-696) is the first primary prevention trial focused on lipid-lowering therapy in patients with diabetes. Over 2800 patients with diabetes, at least one risk factor (ie, HTN, retinopathy) and baseline LDL of less than 160 mg/dl were randomized to atorvastatin (Lipitor) 10 mg or placebo. At 4 years, patients in the atorvastatin arm experienced fewer MIs or strokes with a number needed to treat of 32 compared to placebo.

Practice guideline: Aspirin therapy for patients with DM > 40 years of age

A meta-analysis of 145 prospective controlled trials of anti-platelet therapy in men and women after myocardial infarction, stroke or transient ischemic attack, or positive cardiovascular history (vascular surgery, angioplasty, angina, etc.) has been reported by the Anti-Platelet Trialists (APT). Reductions in vascular events were about one-quarter in each of these categories, and diabetic subjects had risk reductions that were comparable to non-diabetic individuals. There was a trend toward increased risk reductions with doses of aspirin of 325 mg/day or less. It was estimated that 38 ± 12 vascular events per 1,000 diabetic patients would be prevented if they were treated with aspirin as a secondary prevention strategy. Comparable results were seen in males and females.
These results are supported by the Early Treatment Diabetic Retinopathy Study (ETDRS). This population consisted of type 1 and type 2 diabetic men and women, about 48% of whom had a history of cardiovascular disease. The study, therefore, may be viewed as a mixed primary and secondary prevention trial. The relative risk for myocardial infarction in the first 5 years in those randomized to aspirin therapy was lowered significantly to 0.72 (CI 0.55–0.95).
The Hypertension Optimal Treatment (HOT) Trial examined the effects of 75 mg/day of aspirin vs. placebo in 18,790 hypertensive patients who were randomized to achieve diastolic blood pressure goals of 90, 85, or 80 mmHg. There were 1,501 diabetic subjects in this trial. Aspirin significantly reduced cardiovascular events by 15% and myocardial infarction by 36%. The relative effects of aspirin were similar in non-diabetic and diabetic subjects. Fatal bleeding episodes including intracerebral bleeding were equal in the aspirin and placebo groups, while nonfatal minor bleeding episodes were more common in the aspirin group. This study provides further evidence for the efficacy and safety of aspirin therapy in diabetic patients with well-controlled hypertension [v].
The U.S. Physicians’ Health Study was a primary prevention trial in which a low dose aspirin regimen (325 mg every other day) was compared with placebo in male physicians. There was a 44% risk reduction in the treated group, and subgroup analyses in the diabetic physicians revealed a reduction in myocardial infarction from 10.1% (placebo) to 4.0% (aspirin), yielding a relative risk of 0.39 for the diabetic men on aspirin therapy.

Practice guideline: Urinary microalbumin measured annually in patients with DM, with ACE inhibitor or ARB prescribed for patients with microalbuminuria

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Because of the high proportion of patients who progress from microalbuminuria to overt nephropathy and subsequently to ESRD, use of ACE inhibitors or ARBs is recommended for all patients with microalbuminuria or advanced stages of nephropathy. The effect of ACE inhibitors appears to be a class effect, so choice of agent may depend on cost and compliance issues. Many studies have shown that in hypertensive patients with type 1 diabetes, ACE inhibitors can reduce the level of albuminuria and the rate of progression of renal disease to a greater degree than other antihypertensive agents that lower blood pressure by an equal amount. Other studies have shown that there is benefit in reducing the progression of microalbuminuria in normotensive patients with type 1 diabetes and normotensive and hypertensive patients with type 2 diabetes.

Screening for microalbuminuria can be performed by three methods: 1) measurement of the albumin-to-creatinine ratio in a random spot collection; 2) 24-h collection with creatinine, allowing the simultaneous measurement of creatinine clearance; and 3) timed (e.g., 4-h or overnight) collection. Microalbuminuria is present if urinary albumin excretion is greater than or equal to 30 mg/24 h (equivalent to 20 µg/min on a timed specimen or 30 mg/g creatinine on a random sample). Short-term hyperglycemia, exercise, urinary tract infections, marked hypertension, heart failure, and acute febrile illness can cause transient elevations in urinary albumin excretion. If assays for microalbuminuria are not readily available, screening with reagent tablets or dipsticks for microalbumin is an alternative. Because reagent strips only indicate concentration and do not correct for creatinine as the spot urine albumin-to-creatinine ratio does, they are subject to possible errors from alterations in urine concentration. All positive tests by reagent strips or tablets should be confirmed by more specific methods. There is also marked day-to-day variability in albumin excretion, so at least two of three collections done in a 3- to 6-month period should show elevated levels before designating a patient as having microalbuminuria.

Definitions of abnormalities in albumin excretion

Additional resource: Diabetic Nephropathy [vi]