NAC OSCE Clinical Reasoning & Diagnosis 2 — Questions and Answers
Question 1: 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?
- IV alteplase (tPA) if no contraindications, with consideration of thrombectomy if large vessel occlusion is confirmed (Correct answer)
- Immediate anticoagulation with heparin
- Aspirin 325 mg only and admit for monitoring
- CT angiography alone without thrombolytics
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 2: A 50-year-old male with type 2 diabetes has a fasting glucose of 7.4 mmol/L and HbA1c of 6.8% on two separate occasions. According to Diabetes Canada guidelines, what is the diagnosis?
- Type 2 diabetes mellitus (FPG ≥7.0 mmol/L or HbA1c ≥6.5% on two occasions) (Correct answer)
- Impaired fasting glucose only
- Normal glycaemia — repeat in 1 year
- Prediabetes requiring lifestyle intervention only
Correct answer: Type 2 diabetes mellitus (FPG ≥7.0 mmol/L or HbA1c ≥6.5% on two occasions)
Diabetes Canada 2023 guidelines define diabetes as FPG ≥7.0 mmol/L or HbA1c ≥6.5% on two separate occasions in asymptomatic individuals, both criteria met here.
Question 3: A 3-year-old child presents with a barking cough, stridor at rest, and subcostal retractions. Which clinical scoring system is used to assess severity in Canadian paediatric emergency departments?
- Westley Croup Score (Correct answer)
- PEWS (Paediatric Early Warning Score)
- CURB-65
- Pediatric Respiratory Assessment Measure (PRAM)
Correct answer: Westley Croup Score
The Westley Croup Score assesses stridor, retractions, air entry, cyanosis, and level of consciousness to grade croup severity and guide dexamethasone dosing, as used in Canadian paediatric centres.
Question 4: A 22-year-old male university student presents with fever, neck stiffness, and a petechial rash. What is the MOST critical immediate action?
- Administer IV ceftriaxone immediately without waiting for lumbar puncture results (Correct answer)
- Perform lumbar puncture first before any antibiotics
- Isolate the patient and wait for blood cultures before treatment
- Order a CT head before any intervention
Correct answer: Administer IV ceftriaxone immediately without waiting for lumbar puncture results
Bacterial meningitis with purpuric or petechial rash (suggesting meningococcaemia) is a time-critical emergency; Canadian guidelines recommend immediate antibiotics (ceftriaxone) without delay for LP, as a 1-hour delay worsens mortality.
Question 5: A 55-year-old woman with rheumatoid arthritis on methotrexate presents with a new dry cough and dyspnoea. CXR shows bilateral interstitial infiltrates. What is the MOST important diagnosis to exclude?
- Methotrexate-induced pneumonitis (Correct answer)
- Community-acquired pneumonia
- Pulmonary embolism
- Pleural effusion from RA
Correct answer: Methotrexate-induced pneumonitis
Methotrexate pneumonitis is an idiosyncratic drug reaction causing interstitial lung disease; methotrexate must be stopped and the diagnosis confirmed with HRCT and possibly BAL, as continued use can be fatal.
Question 6: According to Canadian Cardiovascular Society (CCS) guidelines, which cardiac troponin result pattern is consistent with acute myocardial infarction using high-sensitivity troponin assays?
- A rise and/or fall pattern with at least one value above the 99th percentile URL, in the clinical context of ischaemia (Correct answer)
- A single elevated troponin value at any time point
- A troponin value greater than three times the upper reference limit only
- Troponin must be elevated on both 0-hour and 6-hour samples to diagnose MI
Correct answer: A rise and/or fall pattern with at least one value above the 99th percentile URL, in the clinical context of ischaemia
CCS and the Universal Definition of MI require a rise and/or fall in troponin with at least one value above the 99th percentile URL, interpreted alongside clinical symptoms and ECG findings.
NAC OSCE Clinical Reasoning & Diagnosis 2
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?