NAC OSCE Exam — Questions and Answers

Question 1: A 65-year-old male has asymmetric leg swelling and calf tenderness. Which bedside test is used to assess for deep vein thrombosis, and what is its sensitivity?

Homan's sign — high sensitivity (>90%), confirms DVT
McMurray's test — assesses for meniscal pathology
Thompson's test — tests for Achilles tendon rupture
Homans' sign — however, it has low sensitivity (~50%) and is no longer recommended as reliable (Correct answer)

Correct answer: Homans' sign — however, it has low sensitivity (~50%) and is no longer recommended as reliable

Homans' sign (pain on dorsiflexion) is historically taught but has poor sensitivity (~50%) and specificity; Canadian guidelines recommend clinical scoring (Wells score) combined with D-dimer or imaging instead.

Question 2: A 25-year-old woman presents with fatigue, weight gain, cold intolerance, and constipation. Her TSH is elevated and free T4 is low. What is the diagnosis and most common cause in Canada?

Cushing's syndrome
Hyperthyroidism — likely Graves' disease
Hypothyroidism — most commonly Hashimoto's thyroiditis (autoimmune thyroiditis) in Canada (Correct answer)
Adrenal insufficiency

Correct answer: Hypothyroidism — most commonly Hashimoto's thyroiditis (autoimmune thyroiditis) in Canada

Elevated TSH with low free T4 confirms primary hypothyroidism. In Canada (and other iodine-sufficient countries), the most common cause is Hashimoto's thyroiditis (chronic autoimmune thyroiditis), confirmed by positive anti-TPO antibodies. Worldwide, iodine deficiency is the most common cause, but in Canada, autoimmune thyroiditis predominates.

Question 3: A 4-year-old child is brought in with a limp. On examination, the hip is held in flexion, abduction, and external rotation. What is the MOST likely diagnosis?

Developmental dysplasia of the hip
Transient synovitis
Legg-Calvé-Perthes disease
Septic arthritis of the hip (Correct answer)

Correct answer: Septic arthritis of the hip

Septic arthritis presents with the hip held in the position of maximum capsular volume (flexion, abduction, external rotation) and is a surgical emergency; fever and elevated inflammatory markers distinguish it from transient synovitis.

Question 4: A 68-year-old woman with atrial fibrillation presents with acute onset left-sided weakness and facial droop of 90 minutes' duration. Her CT head is normal. What is the MOST appropriate immediate management?

Aspirin 325 mg only and admit for monitoring
Immediate anticoagulation with heparin
CT angiography alone without thrombolytics
IV alteplase (tPA) if no contraindications, with consideration of thrombectomy if large vessel occlusion is confirmed (Correct answer)

Correct answer: IV alteplase (tPA) if no contraindications, with consideration of thrombectomy if large vessel occlusion is confirmed

Heart and Stroke Foundation of Canada and Canadian Stroke Best Practices recommend IV tPA within 4.5 hours of symptom onset if there are no contraindications; CT angiography to identify LVO guides thrombectomy decision.

Question 5: When taking a sexual history in the NAC OSCE, which approach is considered BEST practice?

Normalize the questions, use non-judgemental language, ask about gender of partners, contraception, STI history, and ensure confidentiality (Correct answer)
Only ask about sexual history if the patient has genital symptoms
Avoid the topic as it is too personal
Ask the patient to fill out a questionnaire instead

Correct answer: Normalize the questions, use non-judgemental language, ask about gender of partners, contraception, STI history, and ensure confidentiality

A sexual history is a routine part of a complete medical assessment. Best practice includes normalizing ('I ask all my patients these questions'), using non-judgemental inclusive language, asking about the gender of sexual partners, number of partners, contraception use, STI testing and history, and ensuring confidentiality. The NAC OSCE assesses comfort and competence in this area.

Question 6: During a breast examination in a Canadian NAC OSCE station, which feature of a palpable mass is MOST associated with malignancy?

Hard, irregular, non-tender, fixed mass with skin dimpling (Correct answer)
Bilateral tender nodularity worse premenstrually
A fluctuant mass with overlying erythema
Soft, mobile, tender, smooth-bordered mass

Correct answer: Hard, irregular, non-tender, fixed mass with skin dimpling

Malignant breast masses are typically hard, irregular, non-tender, and fixed to surrounding tissue, with skin dimpling (peau d'orange) from Cooper's ligament involvement.

Question 7: A patient presents with shortness of breath. Which question BEST helps differentiate between cardiac and pulmonary causes?

Have you travelled recently?
Do you smoke cigarettes?
Is the shortness of breath worse when lying flat (orthopnea) and do you wake up at night gasping for air (paroxysmal nocturnal dyspnea)? (Correct answer)
What colour is your sputum?

Correct answer: Is the shortness of breath worse when lying flat (orthopnea) and do you wake up at night gasping for air (paroxysmal nocturnal dyspnea)?

Orthopnea (breathlessness when lying flat) and paroxysmal nocturnal dyspnea (PND — waking from sleep with breathlessness) are classic features of heart failure. While they can occur in severe lung disease, these symptoms specifically suggest fluid redistribution when supine, pointing to a cardiac cause. This distinction is critical for guiding further investigation.

Question 8: A physician is asked to complete a medical-legal report for a patient involved in a motor vehicle accident. What is the physician's primary obligation according to the CPSO and CMA?

To refuse all medical-legal work as it creates conflicts of interest
To provide an honest, objective, and accurate report based on clinical findings — not to advocate for the patient's legal position (Correct answer)
To defer entirely to the patient's lawyer for framing the report
To support the patient's claim as their treating physician

Correct answer: To provide an honest, objective, and accurate report based on clinical findings — not to advocate for the patient's legal position

CMA guidelines on medical-legal reporting require physicians to be impartial and accurate; a treating physician's duty in a medico-legal context is to the truth and the court, not to advocate for the patient.

Question 9: A 70-year-old patient with COPD presents in acute hypercapnic respiratory failure (pH 7.28, pCO₂ 78 mmHg, SpO₂ 84%). According to Canadian Thoracic Society guidelines, what is the FIRST-line ventilatory support?

Non-invasive positive pressure ventilation (NIV/BiPAP) (Correct answer)
Controlled low-flow oxygen at 2 L/min only
High-flow nasal oxygen at 60 L/min
Immediate intubation and mechanical ventilation

Correct answer: Non-invasive positive pressure ventilation (NIV/BiPAP)

CTS guidelines recommend NIV (BiPAP) as first-line for acute hypercapnic respiratory failure in COPD exacerbation; it reduces intubation rates and mortality compared to conventional oxygen therapy.

Question 10: A 3-year-old child is brought to the ED with 48 hours of profuse watery diarrhoea and vomiting. She is listless, has sunken eyes, no tears, and dry mucous membranes. Using the WHO/CPS dehydration scale, what is her dehydration status and MOST appropriate initial management?

Mild dehydration — encourage breastfeeding and monitor at home
Severe dehydration (>10% body weight) — IV rehydration with 20 mL/kg NS bolus, reassess and repeat as needed (Correct answer)
Severe dehydration — immediate blood transfusion
Moderate dehydration — oral rehydration solution only

Correct answer: Severe dehydration (>10% body weight) — IV rehydration with 20 mL/kg NS bolus, reassess and repeat as needed

Listlessness, sunken eyes, no tears, and dry mucous membranes indicate severe dehydration (>10%); CPS guidelines recommend immediate IV fluid resuscitation with 20 mL/kg isotonic saline boluses, reassessing after each.

Question 11: When interviewing a patient who is a poor historian, which technique is MOST effective?

Ask a colleague to take the history instead
Skip the history and proceed directly to investigations
Use open-ended questions initially, then focused closed questions, summarize frequently, and use collateral information from family or records (Correct answer)
Ask only yes/no questions to speed up the interview

Correct answer: Use open-ended questions initially, then focused closed questions, summarize frequently, and use collateral information from family or records

With poor historians, begin with open-ended questions to let them share what they can, then use focused questions to fill gaps. Summarize frequently to verify accuracy. Collateral information from family, caregivers, or medical records is invaluable. This structured approach maximizes information gathering while maintaining patient dignity.

Question 12: A 30-year-old woman presents with a unilateral, throbbing headache with nausea and photophobia. She reports seeing zigzag lines before the headache started. What is the MOST likely diagnosis?

Meningitis
Cluster headache
Tension-type headache
Migraine with aura — the visual symptoms (scintillating scotoma) preceding the headache are characteristic (Correct answer)

Correct answer: Migraine with aura — the visual symptoms (scintillating scotoma) preceding the headache are characteristic

This presentation is classic for migraine with aura: visual aura (zigzag lines/scintillating scotoma) preceding a unilateral throbbing headache, accompanied by nausea and photophobia. The aura typically lasts 20-60 minutes. Important considerations include the use of oral contraceptives (increased stroke risk in migraine with aura) and ruling out more serious causes if this is a first presentation.

NAC OSCE Exam

The National Assessment Collaboration Objective Structured Clinical Examination (NAC OSCE) evaluates international medical graduates on clinical skills including history taking, physical examination, clinical reasoning, and communication skills required for Canadian medical licensure.

Questions

240 min

Time Limit

65%

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