The Royal College of Pathologists of Australasia has finished a ground-breaking project to streamline pharmacogenomics (PGx) testing around the country.
The document provides standardised guidelines for clinicians and health professionals on when to consider PGx testing for 35 commonly used medications.
Nationally, an estimated 250,000 hospital admissions each year are a direct result of medication-related problems, costing the health care system approximately $1.4 billion, yet two-thirds of these were potentially preventable.
PGx testing examines how an individual’s genes affect their response to medications to personalise treatment and enhance therapeutic outcomes. However, the lack of standardised guidelines for when to perform PGx testing has been a longstanding challenge in clinical practice.
Over the course of the project, which started n 2022, a multidisciplinary advisory group comprising experts in pathology, pharmacology, and prescribing practice, reviewed international and Australian guidelines, approved product labels, and prescribing guidance to develop the national indications for PGx testing.
Associate Professor Luke Hesson, who co-chaired the RCPA’s PGx Advisory Group, said PGx was growing as a field and there were now many medications with prescribing guidance based on the results of PGx testing.
“This RCPA resource will help doctors to identify when to consider PGx testing and which genes to test. By using PGx testing, we can provide patients with the correct choice and dose of medication,” he said.
Genetic variation could affect:
- pharmacokinetics – how the drug metabolised by the body was affected by genetic variations in metabolising enzymes
- pharmacodynamics – what effect the drug has on the body was influenced by genetic variations in drug targets (such as receptors).
Genetic variations could give rise to four different phenotypes in terms of drug response:
- Poor metabolisers who have markedly reduced or absent enzyme
- Intermediate metabolisers with reduced enzyme
- Extensive (or normal)
- Ultrarapid metabolisers who have high enzyme
Pharmacogenomic testing should be considered for patients with:
- significant side-effects from drugs for which pharmacogenomic variation in response is known
- poor therapeutic response to specific medications
- potential suitability for using doses outside the usual range.
“PGx testing in Australia is reasonably well developed in terms of the range of medications and genes tested,” Professor Hesson said. “However, there needs to be Medicare rebates for PGx tests in Australia, especially given that some of these tests are important for identifying patients at serious risk of toxicity.”
There are currently only two pharmacogenetic tests funded through an MBS rebate: MBS item 73327 for the detection of genetic variants in the thiopurine S-methyltransferase gene for the prevention of dose-related toxicity during treatment with thiopurine drugs; and MBS item 73323 for HLAB5701 testing prior to prescribing Abacavir therapy.
As part of the project, the RCPA has submitted two applications to the Medical Services Advisory Committee to request public funding for DPYD genotyping to predict fluoropyrimidine-induced toxicity and Human leukocyte antigen testing for sensitivity to carbamazepine in patients with epilepsy.
These applications are being assessed, with decisions expected next year.