Electrolytes, enzymes, cardiac markers and hormones

50 Lab technician recruitment practice questions on Electrolytes, enzymes, cardiac markers and hormones, part of Clinical Biochemistry. The first 25 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

Question 1 · Easy
Chloride in sweat is measured to diagnose:
1. AConn syndrome
2. BCystic fibrosis
3. CAddison disease
4. DDiabetes insipidus
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Answer: B · Cystic fibrosis
Sweat is collected after pilocarpine iontophoresis and its chloride measured. A sweat chloride of 60 mmol/L or more supports cystic fibrosis. The defect is in the CFTR chloride channel, so sweat ducts cannot reabsorb chloride. Enough sweat must be collected for a valid result.
- A: Conn syndrome is tested with aldosterone and renin.
- C: Addison disease is tested with cortisol and ACTH.
- D: Diabetes insipidus is tested with urine and plasma osmolality.
Question 2 · Easy
The CK isoenzyme found mainly in heart muscle is:
1. ACK-MM
2. BCK-MB
3. CCK-BB
4. DMacro-CK
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Answer: B · CK-MB
CK is a dimer of M and B subunits. CK-MB makes up about 15-20% of heart CK but little of skeletal muscle CK. CK-MM is the main form in skeletal muscle and in serum. CK-BB comes mainly from brain, prostate and bowel.
- A: CK-MM is the main skeletal muscle isoenzyme.
- C: CK-BB is the brain isoenzyme.
- D: Macro-CK is CK bound to immunoglobulin, not a tissue form.
Question 3 · Medium
An air bubble left in an ABG syringe causes:
1. AFalsely low pCO2
2. BFalsely low pH
3. CFalsely low pO2
4. DFalsely high pCO2
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Answer: A · Falsely low pCO2
Room air has almost no CO2, so CO2 diffuses from blood into the bubble and pCO2 falls. The pH then rises. pO2 moves toward room-air pO2 of about 150 mmHg. Bubbles should be expelled at once and the syringe capped.
- B: Losing CO2 raises, not lowers, pH.
- C: pO2 tends to rise toward the room-air value.
- D: CO2 moves out of the blood, so pCO2 falls.
Question 4 · Easy
Most thyroxine in plasma is carried by:
1. ATransferrin
2. BTransthyretin
3. CThyroxine-binding globulin
4. DAlbumin
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Answer: C · Thyroxine-binding globulin
About 70% of T4 is bound to thyroxine-binding globulin (TBG), with the rest on transthyretin and albumin. Only about 0.03% is free and active. Pregnancy and estrogens raise TBG and total T4 without changing free T4. This is why free T4 is preferred.
- A: Transferrin carries iron, not thyroid hormone.
- B: Transthyretin carries about 10-15% of T4.
- D: Albumin carries only about 10-15% of T4.
Question 5 · Easy
The cardiac marker of choice for diagnosing acute myocardial infarction is:
1. ACardiac troponin
2. BTotal CK
3. CMyoglobin
4. DAST
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Answer: A · Cardiac troponin
Cardiac troponin I or T is specific to heart muscle and is the marker in the universal definition of MI. A rise or fall with a value above the 99th percentile of a healthy population, with ischemia, defines MI. High-sensitivity assays detect it within a few hours. It stays raised for 7-14 days.
- B: Total CK also rises with skeletal muscle injury.
- C: Myoglobin is early but not heart specific.
- D: AST is found in liver and muscle and is obsolete for MI.
Question 6 · Easy
The preferred anticoagulant for an arterial blood gas sample is:
1. AEDTA
2. BSodium citrate
3. CSodium fluoride
4. DHeparin
Answer and explanation in LearnFree account
Question 7 · Hard
An ABG shows pH 7.30, pCO2 28 mmHg and HCO3 13 mmol/L. How is it best interpreted?
1. AMetabolic acidosis with respiratory compensation
2. BRespiratory acidosis with renal compensation
3. CMixed respiratory and metabolic alkalosis
4. DRespiratory alkalosis with renal compensation
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Question 8 · Easy
Thyroid hormones are synthesised from iodine and the amino acid:
1. ATyrosine
2. BTryptophan
3. CHistidine
4. DPhenylalanine
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Question 9 · Easy
The best single first-line test for thyroid function is:
1. ATotal T4
2. BTotal T3
3. CThyroglobulin
4. DTSH
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Question 10 · Hard
A patient has low TSH, low free T4 and low free T3 after pituitary surgery. What is the diagnosis?
1. ASubclinical hyperthyroidism
2. BT3 thyrotoxicosis
3. CPrimary hypothyroidism
4. DCentral hypothyroidism
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Question 11 · Medium
What thyroid profile shows primary hypothyroidism?
1. AHigh TSH, low free T4
2. BLow TSH, low free T4
3. CLow TSH, high free T4
4. DHigh TSH, high free T4
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Question 12 · Medium
Why is hypokalemia hard to correct while hypomagnesemia persists?
1. APotassium binds to albumin
2. BAldosterone secretion stops
3. CPotassium cannot enter cells
4. DRenal potassium loss continues
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Question 13 · Medium
After a myocardial infarction, which marker stays raised the longest?
1. ACK-MB
2. BTroponin
3. CTotal CK
4. DMyoglobin
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Question 14 · Medium
In the CK-NAC method, why is N-acetylcysteine added?
1. ATo remove ATP
2. BTo reactivate CK thiol groups
3. CTo inhibit adenylate kinase
4. DTo chelate magnesium
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Question 15 · Medium
A potassium of 9.8 mmol/L with calcium below 1.0 mmol/L in a well patient most likely reflects:
1. AHemolysis only
2. BHyperaldosteronism
3. CEDTA contamination
4. DAcute renal failure
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Question 16 · Easy
Serum amylase is an enzyme that hydrolyses:
1. APeptide bonds of proteins
2. BAlpha-1,4 glycosidic bonds
3. CEster bonds of triglycerides
4. DPhosphate ester bonds
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Question 17 · Hard
Calculate serum osmolality as 2Na + glucose/18 + BUN/2.8 when Na is 130 mmol/L, glucose 180 mg/dL and BUN 28 mg/dL.
1. A260 mOsm/kg
2. B270 mOsm/kg
3. C150 mOsm/kg
4. D280 mOsm/kg
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Question 18 · Easy
Sodium and potassium in serum are measured in most analyzers by:
1. AIon-selective electrodes
2. BAtomic absorption
3. CNephelometry
4. DColorimetry with dyes
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Question 19 · Medium
Severe diarrhea typically causes:
1. AHigh anion gap acidosis
2. BMetabolic alkalosis
3. CRespiratory alkalosis
4. DNormal anion gap acidosis
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Question 20 · Hard
Total CK is 12,000 U/L with CK-MB 2% of total after a marathon. Troponin is normal. Which is most likely?
1. ASkeletal muscle injury
2. BAcute myocardial infarction
3. CMacro-CK type 1
4. DMyocarditis
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Question 21 · Easy
In the body, most bicarbonate filtered by the kidney is reabsorbed in the:
1. ALoop of Henle
2. BCollecting duct
3. CDistal tubule
4. DProximal tubule
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Question 22 · Hard
A patient has Na 140, Cl 100 and HCO3 10 mmol/L. What is the anion gap?
1. A50 mmol/L
2. B30 mmol/L
3. C20 mmol/L
4. D40 mmol/L
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Question 23 · Medium
A blood sample for potassium was left unseparated in a refrigerator overnight. What change is expected?
1. APotassium rises falsely
2. BSodium rises sharply
3. CPotassium is unchanged
4. DPotassium falls falsely
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Question 24 · Medium
Why is an ABG sample sent on ice if it cannot be analysed within about 30 minutes?
1. ATo preserve heparin
2. BTo prevent clotting
3. CTo slow cell metabolism
4. DTo stop CO2 escaping
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Question 25 · Hard
Serum potassium is 6.9 mmol/L on a sample drawn from a patient with a platelet count of 1,200 x 10^9/L; the ECG is normal. What should the laboratory do?
1. ARepeat with a fluoride tube
2. BReport as true hyperkalemia
3. CDilute and repeat the serum
4. DRepeat on heparin plasma
Answer and explanation in LearnFree account

25 more Electrolytes, enzymes, cardiac markers and hormones questions

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Study Clinical Biochemistry

Electrolytes, enzymes, cardiac markers and hormones

Chloride in sweat is measured to diagnose:

The CK isoenzyme found mainly in heart muscle is:

An air bubble left in an ABG syringe causes:

Most thyroxine in plasma is carried by:

The cardiac marker of choice for diagnosing acute myocardial infarction is:

The preferred anticoagulant for an arterial blood gas sample is:

An ABG shows pH 7.30, pCO2 28 mmHg and HCO3 13 mmol/L. How is it best interpreted?

Thyroid hormones are synthesised from iodine and the amino acid:

The best single first-line test for thyroid function is:

A patient has low TSH, low free T4 and low free T3 after pituitary surgery. What is the diagnosis?

What thyroid profile shows primary hypothyroidism?

Why is hypokalemia hard to correct while hypomagnesemia persists?

After a myocardial infarction, which marker stays raised the longest?

In the CK-NAC method, why is N-acetylcysteine added?

A potassium of 9.8 mmol/L with calcium below 1.0 mmol/L in a well patient most likely reflects:

Serum amylase is an enzyme that hydrolyses:

Calculate serum osmolality as 2Na + glucose/18 + BUN/2.8 when Na is 130 mmol/L, glucose 180 mg/dL and BUN 28 mg/dL.

Sodium and potassium in serum are measured in most analyzers by:

Severe diarrhea typically causes:

Total CK is 12,000 U/L with CK-MB 2% of total after a marathon. Troponin is normal. Which is most likely?

In the body, most bicarbonate filtered by the kidney is reabsorbed in the:

A patient has Na 140, Cl 100 and HCO3 10 mmol/L. What is the anion gap?

A blood sample for potassium was left unseparated in a refrigerator overnight. What change is expected?

Why is an ABG sample sent on ice if it cannot be analysed within about 30 minutes?

Serum potassium is 6.9 mmol/L on a sample drawn from a patient with a platelet count of 1,200 x 10^9/L; the ECG is normal. What should the laboratory do?