l and fungal infections, and delayed wound healing. Some patients can also complain of numbness or tingling in their hands or feet or with blurred vision.
These patients can have modest hyperglycemia, which can proceed to severe hyperglycemia or ketoacidosis due to infection or stress. T1DM patients can often present with ketoacidosis (DKA) coma as the first manifestation in about 30% of patients.
The height, weight, and body mass index (BMI) of patients with diabetes mellitus should be recorded. Retinopathy needs to be excluded in such patients by an ophthalmologist. All pulses should be palpated to examine for peripheral arterial disease. Neuropathy should be ruled out by physical examination and history.
Persons older than 40 years of age should be screened annually. More frequent screening is recommended for individuals with additional risk factors for diabetes.
- Certain races/ethnicities (Native American, African American, Hispanics, or Asian American, Pacific Islander),
- Overweight or obese persons with a BMI greater than or equal to 25 kg/m2 or 23 kg/m2 in Asian Americans,
- First-degree relative with diabetes mellitus
- History of cardiovascular disease or hypertension
- Low HDL-cholesterol or hypertriglyceridemia,
- Women with polycystic ovarian syndrome
- Physical inactivity
- Conditions associated with insulin resistance, for example, Acanthosis nigricans.
Women diagnosed with gestational diabetes mellitus (GDM) should have lifelong testing at least every three years. For all other patients, testing should begin at age 45 years, and if results are normal, patients should be tested at a minimum of every 3-years.
The same tests are used to both screen for and diagnose diabetes. These tests also detect individuals with prediabetes.
Diabetes can be diagnosed either by the hemoglobin A1C criteria or plasma glucose concentration (fasting or 2-hour plasma glucose).
Fasting Plasma Glucose (FPG)
A blood sample is taken after an 8 hour overnight fast. As per ADA, fasting plasma glucose (FPG) level of more than 126 mg/dL (7.0 mm/L) is consistent with the diagnosis.
Two-Hour Oral Glucose Tolerance Test (OGTT)
In this test, the plasma glucose level is measured before and 2 hours after the ingestion of 75 gm of glucose. DM is diagnosed if the plasma glucose (PG) level in the 2-hour sample is more than 200 mg/dL (11.1 mmol/L). It is also a standard test but is inconvenient and more costly than FPG and has major variability issues. Patients need to consume a diet with at least 150 g per day of carbohydrates for 3 to 5 days and not take any medications that can impact glucose tolerance, such as steroids and thiazide diuretics.
Glycated Hemoglobin (Hb) A1C
This test gives an average of blood glucose over the last 2 to 3 months. Patients with a Hb A1C greater than 6.5% (48 mmol/mol) are diagnosed as having DM. Hb A1C is a convenient, rapid, standardized test and shows less variation due to pre-analytical variables. It is not much affected by acute illness or stress.
Hb A1C is costly and has many issues, as discussed below, including lower sensitivity. Hb A1C should be measured using the National Glycohemoglobin Standardization Program (NGSP) certified method standardized to Diabetes Control and Complications Trial (DCCT) assay. It is affected by numerous conditions such as sickle cell disease, pregnancy, hemodialysis, blood loss or transfusion, or erythropoietin therapy. It has not been well validated in non-white populations.
Anemia due to deficiency of iron or vitamin B12 leads to spurious elevation of Hb A1C, limiting its use in countries with a high prevalence of anemia. Also, in children and the elderly, the relation between Hb A1C and FPG is suboptimal.
For all of the above tests, if the person is asymptomatic, testing should be repeated later to make a diagnosis of diabetes mellitus.
In patients with classic symptoms of hyperglycemia (increased thirst, increased hunger, increased urination), random plasma glucose more than 200 mg/dL is also sufficient to diagnose DM.
FPG, 2-hour PG during 75-g GTT, and Hb A1C are equall