ABPS ABPS Diagnostic Testing & Interpretation 1 — Questions and Answers
Question 1: A patient's ECG shows a delta wave and shortened PR interval. Which condition does this pattern suggest?
- First-degree AV block
- Wolff-Parkinson-White (WPW) syndrome (Correct answer)
- Left bundle branch block
- Atrial fibrillation
Correct answer: Wolff-Parkinson-White (WPW) syndrome
WPW syndrome results from an accessory conduction pathway (Bundle of Kent) that pre-excites the ventricles, causing the characteristic delta wave and short PR interval on ECG.
Question 2: Which finding on urinalysis is most specific for a urinary tract infection caused by bacteria?
- Proteinuria
- Glucosuria
- Nitrites and leukocyte esterase (Correct answer)
- Hematuria alone
Correct answer: Nitrites and leukocyte esterase
Nitrites (produced by gram-negative bacteria reducing nitrates) combined with leukocyte esterase (indicating pyuria) together have high specificity for bacterial UTI.
Question 3: A chest X-ray shows a unilateral 'ground-glass opacity' pattern in an immunocompromised patient. Which pathogen should be highest on the differential?
- Streptococcus pneumoniae
- Staphylococcus aureus
- Pneumocystis jirovecii (PCP) (Correct answer)
- Klebsiella pneumoniae
Correct answer: Pneumocystis jirovecii (PCP)
Bilateral perihilar ground-glass opacities on CXR in an immunocompromised host (especially HIV with low CD4) are classic for Pneumocystis jirovecii pneumonia.
Question 4: Which serum marker is most useful for monitoring the effectiveness of treatment in a patient with hepatocellular carcinoma?
- CEA (carcinoembryonic antigen)
- PSA (prostate-specific antigen)
- AFP (alpha-fetoprotein) (Correct answer)
- CA 19-9
Correct answer: AFP (alpha-fetoprotein)
AFP is produced by hepatocellular carcinoma cells and is used both as a diagnostic marker and to monitor treatment response and recurrence.
Question 5: An ABG shows pH 7.28, PaCO2 55 mmHg, HCO3 24 mEq/L. How would you classify this acid-base disorder?
- Metabolic acidosis
- Respiratory alkalosis
- Respiratory acidosis (uncompensated) (Correct answer)
- Metabolic alkalosis
Correct answer: Respiratory acidosis (uncompensated)
The low pH with elevated PaCO2 and normal bicarbonate indicates acute (uncompensated) respiratory acidosis, consistent with hypoventilation.
Question 6: In interpreting a screening test, which statistical measure describes the probability that a person with a negative test truly does not have the disease?
- Sensitivity
- Positive predictive value
- Specificity
- Negative predictive value (Correct answer)
Correct answer: Negative predictive value
Negative predictive value (NPV) is the proportion of true negatives among all individuals who tested negative, indicating the probability of being disease-free given a negative result.
ABPS ABPS Diagnostic Testing & Interpretation 1
A patient's ECG shows a delta wave and shortened PR interval.
Which condition does this pattern suggest?