PEBC Diagnostic Procedures 4 — Questions and Answers
Question 1: A patient presents with a serum potassium of 6.2 mmol/L. Which ECG change is expected first?
- Widened QRS complex
- Peaked T waves (Correct answer)
- Flattened P waves
- Sine wave pattern
Correct answer: Peaked T waves
Peaked (tall, narrow) T waves are the earliest ECG manifestation of hyperkalemia, occurring before P wave changes or QRS widening.
Question 2: Which interpretation of a fasting plasma glucose (FPG) result would indicate prediabetes (impaired fasting glucose) according to Canadian guidelines?
- FPG < 5.6 mmol/L
- FPG 5.6–6.9 mmol/L (Correct answer)
- FPG ≥ 7.0 mmol/L on two occasions
- FPG ≥ 11.1 mmol/L with symptoms
Correct answer: FPG 5.6–6.9 mmol/L
A fasting plasma glucose of 6.1–6.9 mmol/L (per Diabetes Canada guidelines) indicates impaired fasting glucose (prediabetes).
Question 3: A 70-year-old patient's serum creatinine is within normal limits but their eGFR is 52 mL/min/1.73m². What does this discrepancy reflect?
- Laboratory error in creatinine measurement
- Age-related decrease in muscle mass leading to lower creatinine production (Correct answer)
- Increased dietary protein intake elevating creatinine
- Fluid overload diluting serum creatinine
Correct answer: Age-related decrease in muscle mass leading to lower creatinine production
Elderly patients have reduced muscle mass and thus lower creatinine production, causing serum creatinine to appear normal despite significantly reduced GFR.
Question 4: A patient is started on methotrexate for rheumatoid arthritis. Which baseline and monitoring tests are essential?
- Serum glucose and HbA1c only
- CBC, LFTs, serum creatinine, and chest X-ray (Correct answer)
- Thyroid function tests and urinalysis
- INR and aPTT only
Correct answer: CBC, LFTs, serum creatinine, and chest X-ray
Methotrexate requires baseline and periodic CBC (bone marrow suppression), LFTs and albumin (hepatotoxicity), renal function, and chest X-ray (pulmonary toxicity) monitoring.
Question 5: Which finding on a urinalysis would most suggest a urinary tract infection?
- Specific gravity 1.010, pH 6.0
- Positive nitrite and positive leukocyte esterase (Correct answer)
- Trace protein and trace glucose
- Specific gravity 1.030 with ketones
Correct answer: Positive nitrite and positive leukocyte esterase
Positive nitrite (bacterial nitrate reduction) combined with positive leukocyte esterase (pyuria) strongly suggests a bacterial urinary tract infection.
Question 6: A pharmacist reviews a patient's PTT (aPTT) result of 90 seconds (reference: 25–35 seconds). The patient is on unfractionated heparin. What does this suggest?
- Subtherapeutic heparin dosing; increase dose
- Supratherapeutic heparin dosing; reduce infusion rate (Correct answer)
- Therapeutic heparin level; no change needed
- The aPTT is the wrong test to monitor heparin
Correct answer: Supratherapeutic heparin dosing; reduce infusion rate
A therapeutic aPTT target for UFH is typically 1.5–2.5 times the control (approximately 60–80 seconds); an aPTT of 90 seconds indicates supratherapeutic dosing requiring dose reduction.
Question 7: A patient's liver function tests show AST 320 U/L, ALT 480 U/L, ALP 105 U/L, and total bilirubin 28 µmol/L. This pattern most suggests:
- Cholestatic liver disease
- Hepatocellular injury (Correct answer)
- Gilbert syndrome
- Obstructive jaundice
Correct answer: Hepatocellular injury
Markedly elevated transaminases (AST, ALT) with only mildly elevated ALP and bilirubin indicates hepatocellular injury (e.g., viral hepatitis, drug-induced liver injury).
PEBC Diagnostic Procedures 4
A patient presents with a serum potassium of 6.2 mmol/L.
Which ECG change is expected first?