AOA Clinical Diagnosis and Laboratory Medicine 3

Question 1

A positive tuberculin skin test (TST) with induration ≥ 5 mm is considered positive in which patient group?

Accepted Answer

HIV-positive patients

Answer

In immunocompromised patients such as those with HIV, a TST induration ≥5 mm is considered positive due to their increased risk of TB reactivation.

Question 2

Which diagnostic criterion confirms polycythemia vera according to WHO guidelines?

Accepted Answer

JAK2 V617F mutation with elevated hemoglobin and low EPO

Answer

WHO criteria require JAK2 V617F or exon 12 mutation plus elevated hemoglobin (>16.5g/dL men, >16g/dL women) and low serum EPO for diagnosis of polycythemia vera.

Question 3

Which set of laboratory values best characterizes acute pancreatitis?

Accepted Answer

Elevated lipase >3× ULN, elevated amylase, normal LFTs

Answer

Acute pancreatitis is diagnosed when lipase exceeds three times the upper limit of normal, often accompanied by elevated amylase; LFTs may be normal unless gallstones are involved.

Question 4

A patient with community-acquired pneumonia has a positive urinary antigen test. Which pathogen does this test most reliably detect?

Accepted Answer

Legionella pneumophila serogroup 1

Answer

The Legionella urinary antigen test specifically detects Legionella pneumophila serogroup 1, which accounts for the majority of Legionnaires' disease cases.

Question 5

In a patient with suspected systemic lupus erythematosus (SLE), which antibody is most specific for the diagnosis?

Accepted Answer

Anti-double-stranded DNA (anti-dsDNA)

Answer

Anti-dsDNA antibodies are highly specific for SLE (>95% specificity) and also correlate with disease activity and lupus nephritis.

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AOA - AOA Board Certified Practice Test

AOA Clinical Diagnosis and Laboratory Medicine 3