The diagnosis of diabetes mellitus is ceain in which of the following situations?
**Core Concept**
Diabetes mellitus is diagnosed based on consistent hyperglycemia confirmed by specific laboratory criteria, particularly fasting plasma glucose (FPG) levels. The diagnosis requires objective, repeatable measurements that rule out transient hyperglycemia due to stress, diet, or other causes.
**Why the Correct Answer is Right**
Option B meets the diagnostic criteria for diabetes mellitus as defined by the American Diabetes Association (ADA). Three successive fasting plasma glucose levels ≥7.0 mmol/L (126 mg/dL) in an asymptomatic, otherwise healthy individual confirm persistent hyperglycemia. This pattern excludes transient elevations due to dieting or stress. The absence of symptoms and normal clinical status supports a diagnosis of type 2 diabetes, which is common in otherwise healthy adults.
**Why Each Wrong Option is Incorrect**
Option A: Oral glucose tolerance test (OGTT) abnormalities in a young woman during dieting may reflect physiological stress or weight loss, not diabetes. Transient hyperglycemia is common in such cases, and diagnosis requires confirmation with repeat testing or other criteria.
Option C: Glucose levels >7.8 mmol/L in gestational diabetes are diagnostic only after a 50-g OGTT, but this value alone does not meet ADA criteria for gestational diabetes. The threshold is 11.1 mmol/L after 50-g load.
Option D: Asymptomatic glycosuria is non-specific and often a result of mild hyperglycemia or dehydration. It does not confirm diabetes and must be followed by plasma glucose testing.
**Clinical Pearl / High-Yield Fact**
Persistent fasting glucose ≥7.0 mmol/L on three separate occasions is the gold standard for diagnosing diabetes mellitus in adults. Always confirm with repeat testing to avoid false positives from stress or diet.
✓ Correct Answer: B. Successive fasting plasma glucose concentrations of 8, 9, and 8.5 mmol/L in an asymptomatic, otherwise healthy businesswoman