AOA Clinical Diagnosis and Laboratory Medicine

Question 1

A 55-year-old man presents with fatigue, pallor, and a mean corpuscular volume (MCV) of 110 fL. Which finding would best confirm megaloblastic anemia?

Accepted Answer

Hypersegmented neutrophils on peripheral smear

Answer

Hypersegmented neutrophils (≥5 lobes) on peripheral smear are a hallmark of megaloblastic anemia due to B12 or folate deficiency.

Question 2

Which laboratory finding is most characteristic of disseminated intravascular coagulation (DIC)?

Accepted Answer

Elevated D-dimer with prolonged PT and PTT

Answer

DIC is characterized by elevated D-dimer (reflecting fibrinolysis), prolonged PT/PTT, and decreased fibrinogen due to widespread coagulation factor consumption.

Question 3

A patient with suspected myocardial infarction presents 6 hours after symptom onset. Which biomarker is most sensitive and specific at this time point?

Accepted Answer

Troponin I

Answer

Troponin I remains elevated for 7–10 days and is the most sensitive and specific cardiac biomarker from 4–6 hours after MI onset.

Question 4

An anion gap of 22 mEq/L is found in a patient with altered mental status. Which condition is the LEAST likely cause of this elevated anion gap?

Accepted Answer

Hyperchloremic metabolic acidosis

Answer

Hyperchloremic metabolic acidosis (e.g., from diarrhea or RTA) is a normal anion gap acidosis, not an elevated anion gap acidosis.

Question 5

Which test is considered the gold standard for diagnosing iron deficiency anemia?

Accepted Answer

Bone marrow iron staining

Answer

Bone marrow iron staining directly visualizes iron stores and is the definitive gold standard, though serum ferritin is the most practical first-line test.

AOA - AOA Board Certified Practice Test

AOA - AOA Board Certified Practice Test

AOA Clinical Diagnosis and Laboratory Medicine