MSRA Core Knowledge and Fundamentals 3 — Questions and Answers
Question 1: Which of the following best describes the mechanism of action of low molecular weight heparin (LMWH)?
- Directly inhibits thrombin (factor IIa) only
- Primarily inhibits factor Xa via antithrombin (Correct answer)
- Inhibits vitamin K epoxide reductase
- Blocks platelet glycoprotein IIb/IIIa receptors
Correct answer: Primarily inhibits factor Xa via antithrombin
LMWH preferentially enhances antithrombin's inhibition of factor Xa compared to unfractionated heparin, which inhibits both Xa and IIa.
Question 2: A 45-year-old woman presents with weight gain, cold intolerance, dry skin, and bradycardia. TSH is 12 mU/L and free T4 is low. What is the diagnosis?
- Subclinical hypothyroidism
- Primary hypothyroidism (Correct answer)
- Secondary hypothyroidism
- Sick euthyroid syndrome
Correct answer: Primary hypothyroidism
Elevated TSH with low free T4 combined with classic symptoms confirms primary hypothyroidism.
Question 3: A 28-year-old man presents with painless lymphadenopathy, night sweats, and a 10% weight loss over 3 months. Biopsy shows Reed-Sternberg cells. What is the diagnosis?
- Non-Hodgkin lymphoma
- Hodgkin lymphoma (Correct answer)
- Infectious mononucleosis
- Sarcoidosis
Correct answer: Hodgkin lymphoma
Reed-Sternberg cells (binucleate giant cells) are pathognomonic for Hodgkin lymphoma.
Question 4: Which renal tubular segment is primarily responsible for concentrating urine?
- Proximal convoluted tubule
- Thin descending limb of loop of Henle
- Collecting duct (under ADH influence) (Correct answer)
- Distal convoluted tubule
Correct answer: Collecting duct (under ADH influence)
ADH acts on the collecting duct to insert aquaporin-2 channels, allowing water reabsorption and urine concentration.
Question 5: A patient with known epilepsy is started on a new medication that reduces the efficacy of their oral contraceptive pill. Which anti-epileptic drug is most likely responsible?
- Valproate
- Levetiracetam
- Carbamazepine (Correct answer)
- Lamotrigine
Correct answer: Carbamazepine
Carbamazepine is a potent inducer of cytochrome P450 enzymes, significantly reducing plasma levels of oestrogen and progestin.
Question 6: Which of the following CSF findings is most consistent with bacterial meningitis?
- Low protein, high glucose, lymphocytosis
- High protein, low glucose, neutrophilia (Correct answer)
- Normal protein, normal glucose, lymphocytosis
- High protein, normal glucose, xanthochromia
Correct answer: High protein, low glucose, neutrophilia
Bacterial meningitis typically causes high CSF protein, very low glucose (<50% serum), and a neutrophil-predominant pleocytosis.
Question 7: A 62-year-old woman with known COPD presents acutely breathless. ABG shows pH 7.28, pCO2 68 mmHg, pO2 50 mmHg. What type of respiratory failure is this?
- Type 1 respiratory failure
- Type 2 respiratory failure (Correct answer)
- Metabolic acidosis
- Compensated respiratory alkalosis
Correct answer: Type 2 respiratory failure
Type 2 respiratory failure is defined by hypoxia (pO2 <8 kPa) with hypercapnia (pCO2 >6 kPa), indicating ventilatory failure.
MSRA Core Knowledge and Fundamentals 3
Which of the following best describes the mechanism of action of low molecular weight heparin (LMWH)?