Clinical Chemistry question bank

Clinical Chemistry
by Medical Educator Clinical Chemistry

Clinical chemistry is a vital aspect of modern medicine that helps healthcare providers diagnose, treat, and monitor a wide range of medical conditions. By analyzing biological specimens such as blood, urine, and other body fluids, clinical chemists are able to determine the presence or absence of specific diseases. The results of these tests play a crucial role in patient care and inform clinical decisions.

If you are curious about this fascinating field and want to test your knowledge, why not try our multiple choice questions below to see how much you already know about clinical chemistry? This question bank is designed to be both educational and interactive, so get ready to test your understanding of this critical area of healthcare.

Table of Contents

Physical sign

A 26 year old female presents with a 3 day history of paraesthesia, weakness and tetany. On arrival to the A&E department she has a tonic clonic seizure.

She recovers some minutes later.

She has recently had surgery in another hospital 3 weeks previously.

She also has a history of nephrotic syndrome.


The A&E consultant demonstrates what he suspects to be the diagnosis by tapping the side of her face with his finger.

What is the name of the Physical sign?

  • Chvostek’s sign
  • Trousseau’s sign
  • Carpopedal Spasm
  • Ann Arbour Sign
  • None of the listed answers

Chvostek’s sign

Chvostek’s sign is tetany of the facial muslces when the facial nerve is tapped. It is associated with hypocalcaemia.

Trousseau’s sign the inflation of a blood pressure cuff >10-20mmHg about systolic pressure, resulting in mild ischaemia and subsequent carpal spasm.

They are both associated with hypocalcaemia.

Hyperkalaemia

A patient is admitted with a broad complex tachycardia and nausea.

An arterial blood gas on admission shows a normal pH and a potassium of 7.6

Observations:
BP110/55
Sats 94% air
BM 7.6

Which of the following would be the best “next step”?

  • IV Calcium gluconate 10ml 10% over 5 minutes
  • IV Insulin & dextrose
  • Repeat urgent lab potassium prior to any treatment
  • Defibrillate
  • IV Beta blocker

IV Calcium gluconate 10ml 10% over 5 minutes

Broad complex tachycardia plus hyperkalaemia = risk of ventricular tachycardia.

ABG machines in hospitals are calibrated daily and although they may not give you a perfectly accurate result for the purposes of clinical practice and an exam it is unsafe to delay treatment whilst waiting (30+) minutes for a lab sample.

The insulin dextrose will lower the K+ but to stabilize the myocardium the calcium gluconate would be the most important step.

What surgery?

A 26 year old female presents with a 3 day history of paraesthesia, weakness and tetany. On arrival to the A&E department she has a tonic clonic seizure.

She recovers some minutes later.

She has recently had surgery in another hospital 3 weeks previously.
She also has a history of nephrotic syndrome.

She has a positive Chvostek’s sign.

What surgery is she most likely to have had recently?

  • Thyroidectomy
  • Nephrectomy
  • Adrenalectomy
  • Renal Biopsy
  • Ileostomy

Thyroidectomy

The diagnosis is hypocalcaemia.

Calcium metabolism is regulated by the parathyroid blangs. In a thyroidectomy the parathyroids can be removed. This resultant lack of PTH (parathyroid hormone) can cause a precipitous drop in the serum calcium.

Hyponatraemia Case

A 75 year old man presents with confusion
He has hyponatraemia (Na+ 115mmol/l (135-145mmol/l))

Drug History
Simvastatin
Bendroflumethiazide
Metoprolol
Fluticasone
Prednisolone
Aspirin
Theophylline
Tiotropium
Salbutamol
Thyroxine

What is the most likely aetiology of the hyponatraemia?

  • Bendroflumethiazide
  • Simvastatin
  • Metoprolol
  • Thyroxine
  • Theophylline

Bendroflumethiazide

BFZ is a common drug cause of hyponatraemia along with citalopram, opiates, haloperidol, other diuretics etc.

Continued from previous question. Unfortunately he is found to have a large cavitating lung lesion on the Chest Xray and a provisional diagnosis of lung malignancy is made. It is felt this is more likely to explain his hyponatraemia.

What would you expect his serum anti diuteric hormone levels to be?

  • High
  • Normal
  • Low

High

This is classic SiADH: syndrome of inappropriate anti diuretic hormaone.

Continued from previous question. What would you expect his serum osmolarity to be?

  • High
  • Normal
  • Low

Low

This is classic SiADH: syndrome of inappropriate anti diuretic hormaone. So you get water retention leading to hyponatraemia and a low serum osmolarity.

Abnormality on ABG

An 62 year old man presents to A&E following a 4 day history of cough.

He feels weak

pH7.327.35-7.45
Pa O26.8>10.6
Pa CO27.74.7-6
HCO32-3220-28
Base excess-2+/- 2

What is the abnormality shown on the ABG?

  • Type 1 respiratory Failure
  • Type 2 respiratory failure
  • Metabolic acidosis
  • Respiratory alkalosis
  • None of the answers listed here

Type 2 respiratory failure

Diagnosis is type 2 respiratory failure.

Type 1 = PO2 <8, Normal CO2

Type 2 = PO2 <8, CO2 >6

Continued from previous question. A further history is taken. He smokes 40 cigarettes a day but has no history of COPD.

In the community prior to his illness what would you expect his bicarbonate to be?

  • Normal
  • High
  • Low
  • Respiratory alkalosis
  • None of the answers listed here

High

His elevated HCO3 suggests metabolic compensation which has occurred over weeks. If there is metabolic compensation the likelihood is its a respiratory acidosis (i.e. retained CO2)

Does this make sense? Yes. He may well have undiagnosed COPD in the community.

Continued from previous question. In the community prior to his admission whilst he was “well” do you suspect his blood pH is?

  • Normal
  • Acidotic
  • Alkalotic
  • Respiratory alkalosis
  • None of the answers listed here

Normal, Acidotic

From any chronic problem compensation will hopefully restore equilibrium. Id expect his pH to be normal as evidenced by his high HCO3.

Most COPD patients in the community during stable episodes will run a normal pH with a high bicarbonate that will be a marker for CO2 retention.

Joint pain case

A 64 year old south asian woman presents to clinic with articular joint pain of her knees and hands.

Her blood tests show the following

Serum Calcium 2.17 (NR 2.2-2.6)
Vitamin D 11 (NR >15)
Albumin 44 (35-45)

She has no neurological abnormalities.
Musculoskeletal examination is unremarkable other than mild crepitus of the knees.

What is the most likely cause for her joint pain?

  • Hypocalcaemia
  • Vitamin D deficiency
  • Hypothyroidism
  • Rheumatoid arthritis
  • None of the listed answers

None of the listed answers

She has a low vitamin D and a slightly low serum calcium.

Although hypocalcaemia can cause…
numbness
osteomalacia
paraesthesia
…the hypocalcaemia is mild.

The vitamin D level is slightly low.

Next question: Does hypocalcaemia cause hand and knee pain? No…

Does hypocalcaemia cause crepitus? No… but OA does. This condition is much more likely here.


Continued from previous question. What is the most likely aetiology of her hypocalcaemia?

  • Addison’s
  • Coeliac Disease
  • Tropical Sprue
  • Hypoparathyroidism
  • None of the listed answers

None of the listed answers

All of the answers could cause hypocalcaemia but none of them are the correct answer.

Vitamin D deficiency is endemic in middle aged asian women in the UK. This may be multifactorial and include factors such as sunlight exposure / diet (certain flours used in preparation of food) and genetic factors.

These are far commoner than the other reasons.

Remember to check though: are any conditions strongly associated with OA? No, so it is likely to be dietary/genetic/environmental.