- Design
- Retrospective prescribing analysis linked to population genome data
- Population
- 1.16 million patients at a Singapore tertiary centre; 9051 sequenced Singaporeans
- Primary outcome
- Annual exposure to CPIC A or A/B drugs; estimated actionable prescriptions
- Effect
- 38.1–43.0% exposed annually; 18.4% estimated actionable
This study combined 2014–2021 prescribing records for 1.16 million patients at a Singapore tertiary hospital with whole-genome data from 9051 Singaporeans to estimate the reach of pre-emptive pharmacogenomic testing. It was published in the British Journal of Clinical Pharmacology in September.
Each year, 38 to 43% of patients received at least one drug with a CPIC level A or A/B gene–drug guideline. Omeprazole, statins and tramadol were the most common; CYP2C19, CYP2D6 and SLCO1B1 were the most implicated genes. Indian and Malay patients received these drugs at younger ages than Chinese patients. The authors estimate 18.4% of patients could have had a prescription modified by pre-emptive testing.
The population includes an ethnic Indian group, so the finding is relevant to Indian prescribers: the common, cheap drugs — PPIs, statins, clopidogrel, codeine and tramadol — are where genotype matters.
- Know the high-yield gene–drug pairs: CYP2C19 with clopidogrel and PPIs, CYP2D6 with codeine and tramadol, SLCO1B1 with simvastatin.
- Use existing genotype results when a patient has them.
- Consider alternatives to codeine and tramadol when response is unexpectedly absent or excessive.
- Prefer a non-simvastatin statin when myopathy develops.
Why it matters
Pharmacogenomic relevance is concentrated in a handful of everyday drugs, not rare specialist ones.
Don't overread it
The 18.4% is a modelled estimate, not evidence that pre-emptive testing improves outcomes.
The statistics, in plain English
The 18.4% figure is modelled by combining prescription data with population variant frequencies; it was not measured in the same patients. It is an upper-bound estimate of actionability, not proof that testing improves outcomes.
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