Likelihood Ratio and Post-Test Probability Calculator
Converts pre-test probability to post-test probability using positive or negative likelihood ratios. Key tool for Bayesian clinical reasoning.
Score interpretation
Post-test probability >75%. Disease strongly probable.
→ Treat empirically or confirm with gold-standard test.
Post-test probability 30-75%. Further testing required.
→ Additional diagnostic workup indicated.
Post-test probability <30%. Disease unlikely.
→ Consider alternative diagnoses. May be safe to rule out.
Interpretation bands for the Likelihood Ratio. Apply clinical judgement and local guidance.
References
- Sackett DL, et al. Evidence-based medicine: how to practice and teach EBM. 2nd ed. Churchill Livingstone; 2000.
Related
Curated clinical cross-links plus same-class fallbacks.
- Lisinopril (HFrEF / Post-MI) · ACE Inhibitor / HFrEF
- Colchicine (Pericarditis / Post-MI Inflammation) · Pericarditis / Coronary Inflammation
- Clopidogrel (ACS / Post-PCI) · Antiplatelet / ACS
- Tetracosactide · Synthetic ACTH (short Synacthen test)
- Urea (13C) · 13C-urea breath test
- Diclofenac (Dysmenorrhoea / Post-gynaecological Procedure) · NSAID — Gynaecological Pain
Featured in these MRCEM clinical pathways
The Likelihood Ratio is covered in detail — with RCEM/NICE evidence base, indications and pitfalls — in the following exam-focused pathways on our sister siteReviseMRCEM.
MRCEM Primary / Intermediate / OSCE candidates: each pathway includes exam-style questions, RCEM/NICE citations, and FAQ summaries.
Decision support only — verify against a current formulary, NICE, or your local guideline before clinical use.