NAC OSCE Diagnostic Investigations & Data Interpretation

Question 1

A 58-year-old woman presents with fatigue and pallor. Labs show Hgb 78 g/L, MCV 112 fL, and hypersegmented neutrophils on peripheral smear. Which of the following is the most likely underlying cause?

Accepted Answer

Vitamin B12 deficiency

Answer

Iron deficiency anemia

Answer

Anemia of chronic disease

Answer

Thalassemia minor

Question 2

A 65-year-old man on hydrochlorothiazide has serum Na 118 mEq/L, serum osmolality 258 mOsm/kg, and urine osmolality 580 mOsm/kg. What is the most likely diagnosis?

Accepted Answer

SIADH

Answer

Diabetes insipidus

Answer

Psychogenic polydipsia

Answer

Cerebral salt wasting

Question 3

A 72-year-old woman presents with confusion, constipation, and polyuria. Her corrected serum calcium is 3.3 mmol/L. Which is the most likely cause of severe hypercalcemia in this clinical context?

Accepted Answer

Malignancy

Answer

Primary hyperparathyroidism

Answer

Vitamin D intoxication

Answer

Sarcoidosis

Question 4

A 40-year-old with alcohol use disorder presents with weakness and muscle cramps. Labs: K+ 2.8 mEq/L, Mg2+ 0.45 mmol/L (low), PO4 0.6 mmol/L. Which electrolyte deficiency must be corrected first to successfully treat the hypokalemia?

Accepted Answer

Magnesium

Answer

Potassium

Answer

Phosphate

Answer

Calcium

Question 5

A diabetic patient's ABG shows pH 7.28, pCO2 22 mmHg, HCO3 10 mEq/L; serum Na 138 mEq/L, Cl 98 mEq/L. What is the calculated anion gap?

Accepted Answer

30 mEq/L

Answer

12 mEq/L

Answer

18 mEq/L

Answer

40 mEq/L

Question 6

A 35-year-old woman presents with fatigue and hair loss. TSH is 12 mU/L (normal 0.4–4.0), free T4 is low, and anti-TPO antibodies are markedly elevated. What is the most likely diagnosis?

Accepted Answer

Hashimoto's thyroiditis

Answer

Graves' disease

Answer

De Quervain thyroiditis

Answer

Central hypothyroidism

Question 7

A 50-year-old man presents with chest pain. Troponin I is 0.08 ng/mL (upper reference limit 0.04 ng/mL). ECG shows no ST changes or new LBBB. What is the most appropriate immediate next step?

Accepted Answer

Repeat troponin in 3–6 hours and continue monitoring

Answer

Discharge with outpatient cardiology follow-up

Answer

Immediate coronary angiography

Answer

Administer thrombolytics