Case Studies
Ed is a 60 year-old man who recently suffered an acute myocardial infarction (MI). To prevent this from happening in the future, Ed's cardiologist recommended antiplatelet therapy and prescribes clopidogrel.
Five months later, Ed has another acute MI. Now his cardiologist suspects that Ed has been non-adherent, or that clopidogrel therapy may have been ineffective.
How would genetic testing help Ed and his cardiologist?
Determining his CYP2C19 genotype may reveal that Ed carries a variant that diminishes the antiplatelet effect of clopidogrel. If this were the case, alternative antiplatelet therapies may have been considered, reducing the chance that he'd suffer a second cardiac event.
Miriam is a 67 year-old woman who has recently been diagnosed with atrial fibrillation. To reduce the risk of stroke and other thrombotic events, her physician recommends warfarin therapy.
To estimate the initial dose, Miriam's clinical characteristics (age, sex, weight, diet) were considered. However, she will need to return to the clinic every day for INR monitoring until a stable dose is determined, and then every few weeks thereafter for maintenance monitoring.
How would genetic testing help Miriam and her physician?
Determination of Miriam's CYP2C9 and VKORC1 genotype would reveal whether she carries any variations that alter her ability to metabolize and respond to warfarin. Knowing about any gene variations before initiating therapy allows for more accurate initial dosing and faster INR stabilization, and can reduce the risk for bleeding or clotting events.
Diane is a 32 year-old woman who gave birth by caesarian section two weeks prior. Her physician prescribed codeine for post-caesarian pain. Despite taking no more than the prescribed dose, she experienced nausea and dizziness while she was taking codeine.
She also noticed that her breastfed infant was lethargic and feeding poorly. When Diane mentioned these symptoms to her physician, he recommended that she discontinue codeine use. Within a few days, both Diane and her infant’s symptoms were no longer present.
How would genetic testing help Diane and her physician?
Genotyping of Diane's CYP2D6 gene may have revealed a duplication of CYP2D6 genes, placing her in the ultra-rapid metabolizer category. Armed with this knowledge, her physician would likely have prescribed a different analgesic that would have spared Diane and her infant the symptoms of opioid toxicity.