PLAB 1 Diagnosis & Investigation Interpretation

Question 1

A 55-year-old man has the following arterial blood gas results: pH 7.28, PaCO2 3.2 kPa, PaO2 12.5 kPa, HCO3 14 mmol/L. What is the most likely acid-base disturbance?

Accepted Answer

Metabolic acidosis with respiratory compensation

Answer

Respiratory acidosis

Answer

Respiratory alkalosis

Answer

Mixed metabolic and respiratory acidosis

Question 2

A 30-year-old woman has blood test results showing: Hb 88 g/L, MCV 70 fL, serum ferritin 6 µg/L, transferrin saturation 8%. What is the most likely diagnosis?

Accepted Answer

Iron deficiency anaemia

Answer

Anaemia of chronic disease

Answer

Thalassaemia trait

Answer

Folate deficiency anaemia

Question 3

A 68-year-old man has a serum sodium of 122 mmol/L. He has gained weight, has peripheral oedema, and his urine sodium is 10 mmol/L. What is the most likely cause?

Accepted Answer

Cardiac failure or nephrotic syndrome causing dilutional hyponatraemia

Answer

SIADH (syndrome of inappropriate ADH)

Answer

Addison's disease

Answer

Diuretic therapy

Question 4

A chest X-ray shows a tracheal deviation to the right, loss of left lung volume, and a raised left hemidiaphragm. What is the most likely diagnosis?

Accepted Answer

Left sided lung collapse (atelectasis)

Answer

Left pneumothorax

Answer

Left sided pleural effusion

Answer

Right pneumothorax

Question 5

A patient's ECG shows: heart rate 150 bpm, narrow complex, no visible P waves, irregularly irregular rhythm. What is the most likely diagnosis?

Accepted Answer

Atrial fibrillation

Answer

Atrial flutter with 2:1 block

Answer

SVT (AVNRT)

Answer

Sinus tachycardia

Question 6

A 25-year-old woman has TFTs showing: TSH <0.01 mIU/L, free T4 35 pmol/L, free T3 12 pmol/L. What do these results indicate?

Accepted Answer

Hyperthyroidism (primary)

Answer

Primary hypothyroidism

Answer

Secondary hypothyroidism

Answer

Sick euthyroid syndrome