The PSA
Section 8 of 8
Data interpretation
Interpret results (drug levels, U&E, FBC, LFTs, nomograms) and change prescribing accordingly.
12 marks · 6% of the exam6 items × 2
What it tests
Read a result, link it to the drug therapy, and decide the prescribing change — stop, hold, reduce, or reverse.
How to tackle it
- 1Interpret the abnormal result first
- 2Connect it to the relevant drug on the chart
- 3Decide the action: stop/hold/reduce the culprit, or give the antidote/treatment
Worked example
K⁺ 6.2 mmol/L in a patient taking ramipril and spironolactone.
Answer
Stop both potassium-raising drugs and treat the hyperkalaemia.
Pitfalls & high-yield
- Common links: rising creatinine → hold nephrotoxics/metformin; high INR → hold warfarin ± vitamin K; low K⁺ on a loop diuretic → replace/review; digoxin toxicity worse with hypokalaemia.
- Always state the *prescribing change*, not just the interpretation.
How it’s marked
2 marks per item, 6 items = 12 of 200 marks. Standard-set per sitting (pass mark ≈ 60–63%, varies).