Stratified medicine versus personalised medicine
Stratified medicine matches treatment to groups of patients who share a characteristic that predicts benefit or harm, whereas personalised medicine tailors care using information about one individual.
Remember
A genetic test that sorts patients into groups before treatment, so that each group gets the drug or dose that suits it, is stratified medicine, while personalised medicine tailors care to the individual. Stratified prescribing (using stratified medicine to guide prescribing) is itself a form of personalised medicine.
The word stratified comes from strata, meaning layers or subgroups, so in stratified medicine a test sorts patients into groups and each group gets the drug or dose that suits it. The groups share a characteristic that predicts benefit or harm. A gene variant (an inherited difference in a gene that changes how a person responds to a drug) is one common basis for the grouping. Pharmacogenetics is the study of how inherited gene variants change the way a person handles or responds to a drug. The characteristic can also be another biological feature of the patient or of their disease.
Many drugs are broken down (metabolised) by liver enzymes, and the gene for such an enzyme can come in versions that work well or poorly. A poor metaboliser, meaning a person who clears the drug slowly, has reduced enzyme activity, so a drug that is active as given builds up to higher levels in the blood and toxicity becomes more likely. Genotyping (testing a person's DNA for the variant) before treatment lets the prescriber place each patient in the right group and give carriers (patients who have the variant) a lower starting dose.
Personalised medicine is the neighbouring idea. It uses relevant information about one individual to tailor care, including targeted genetic or protein tests where appropriate. Whole-genome sequencing is not required for every patient or prescription: stratified prescribing is itself a form of personalised medicine, and a targeted test can define the treatment groups without it.
Timing also matters, because the genetic test comes before treatment, whereas pharmacovigilance (collecting reports of suspected harm once a medicine is in use, for example through the Yellow Card Scheme) looks for harm after a drug is already in use.
Key facts
- Stratified medicine
- treatment is matched to groups of patients who share a characteristic, such as a gene variant, that predicts benefit or harm.
- Personalised medicine
- relevant information about one individual is used to tailor care, and sequencing the whole genome of every patient is not required.
- Targeted test
- a test for specific known variants is usually enough to sort patients into treatment groups.
- Poor metabolisers
- reduced enzyme activity means higher drug levels and more toxicity for drugs that are active as given, so a lower dose may be needed.
- Timing
- the test comes before treatment, unlike pharmacovigilance, which looks for harm after a drug is in use.
- Ancestry
- where testing is advised for patients of certain ancestries because an allele is more common in some populations, ancestry only flags who should be tested, and the genotype, not the ancestry, decides whether the drug is used.
Exam traps
- Starting a usual dose and adjusting it according to how a patient responds is not stratified medicine, because it uses no genetic test before the first dose to place a patient in a group.
- Collecting reports of harm once a medicine is in use is pharmacovigilance, not stratified medicine, because stratified medicine uses a test before prescribing to choose the dose.
- A test for a single variant that places patients into genetic groups, with each group matched to the drug or dose that suits it, is stratified medicine, and it does not require whole-genome sequencing of every patient.
Read the full notes
Tested in 6 SimpleMed+ questions
Practice it in Pharmacology, with the answer and a full explanation after every question.
Practice these questions