What laboratory result confirms a diagnosis of diabetes in a 36-year-old obese woman presenting with fatigue, without symptoms of polydipsia (excessive thirst), polyuria (frequent urination), polyphagia (excessive hunger), or weight loss?

From the Guidelines

To confirm the diagnosis of diabetes in this 36-year-old obese woman with fatigue but without classic symptoms, a fasting plasma glucose ≥126 mg/dL (7.0 mmol/L), a 2-hour plasma glucose ≥200 mg/dL (11.1 mmol/L) during an oral glucose tolerance test, a random plasma glucose ≥200 mg/dL (11.1 mmol/L) with symptoms, or a hemoglobin A1C ≥6.5% would confirm the diagnosis, as stated in the most recent guidelines 1.

The diagnosis of diabetes is established by identifying the presence of hyperglycemia, and the recommended methods for diagnosis include measuring fasting glucose, 2-hour postload glucose during an oral glucose tolerance test, or hemoglobin A1C 1. The absence of classic symptoms such as polydipsia, polyuria, polyphagia, or weight loss does not rule out diabetes, as many patients, particularly with type 2 diabetes, may be asymptomatic or present with nonspecific complaints like fatigue.

Key diagnostic criteria include:

• Fasting plasma glucose ≥126 mg/dL (7.0 mmol/L)
• 2-hour plasma glucose ≥200 mg/dL (11.1 mmol/L) during an oral glucose tolerance test
• Random plasma glucose ≥200 mg/dL (11.1 mmol/L) with symptoms
• Hemoglobin A1C ≥6.5%

Any of these findings should be repeated on a subsequent day to confirm the diagnosis unless symptoms are present with a random glucose ≥200 mg/dL, as recommended by the guidelines 1. Obesity is a significant risk factor for type 2 diabetes due to insulin resistance, and once diagnosed, initial management would typically include lifestyle modifications (diet, exercise, weight loss) and possibly metformin at a starting dose of 500 mg daily, gradually increased to 1000-2000 mg daily in divided doses as tolerated.

It is essential to note that the diagnosis of diabetes requires confirmation, which can be accomplished by repeating the same assay on a different blood sample drawn on a subsequent day or by using a different test, such as glucose or HbA1c, in samples obtained on the same day 1. The most recent guidelines provide clear recommendations for the diagnosis and management of diabetes, and healthcare professionals should follow these guidelines to ensure accurate diagnosis and effective treatment 1.

From the Research

Diagnosis of Diabetes

To confirm a diagnosis of diabetes in a 36-year-old obese woman presenting with fatigue, without symptoms of polydipsia, polyuria, polyphagia, or weight loss, the following laboratory results are relevant:

• A fasting glucose level of 126 mg/dL or higher 2
• A glucose level of 200 mg/dL or higher measured 2 hours after a 75-g oral glucose load 2
• A glycated hemoglobin level (HbA1C) of 6.5% or higher 2, 3

Laboratory Tests

The laboratory tests used to diagnose diabetes include:

• Fasting plasma glucose test
• Oral glucose tolerance test (OGTT)
• HbA1C test These tests can be used individually or in combination to confirm a diagnosis of diabetes 2, 3

HbA1C Test

The HbA1C test is a commonly used diagnostic test for diabetes, with a cut-off value of 6.5% or higher indicating diabetes 2, 3

• The HbA1C test has a specificity of 98.7% but a sensitivity of only 46.8%, meaning that more than half of diabetic subjects may be missed when using this test alone 3
• The HbA1C test should be used in combination with plasma glucose determinations for the diagnosis of diabetes 2

Diagnostic Criteria

The diagnostic criteria for diabetes include:

• Fasting glucose level of 126 mg/dL or higher
• Glucose level of 200 mg/dL or higher measured 2 hours after a 75-g oral glucose load
• HbA1C level of 6.5% or higher These criteria can be used to confirm a diagnosis of diabetes in individuals with symptoms such as fatigue, even in the absence of classic symptoms like polydipsia, polyuria, polyphagia, or weight loss 2, 3