According to FDA statistics, about 2 million Americans take warfarin, also known as Coumadin, the top-used blood thinner. It helps in preventing potentially dangerous blood clots that can cause strokes. Proper dose of warfarin is estimated by trial and error method which is very risky because small dose will increase risk of stroke while high dose can lead to fatal bleeding. Recent study showed that a DNA test can help in determining proper dosage of warfarin for a patient.

Researchers in nine countries collected data about 5,700 patients already taking warfarin. They also studied variants of two genes: CYP2C9, which affects how the liver activates and excretes warfarin, and VKORC1, which activates vitamin K, essential for blood clotting. With the help of data analysis, researchers created to an algorithm that could predict the ideal dose of warfarin.

Co-author Teri Klein, a senior research scientist in genetics at Stanford said: "We found, based on this population, which is 46 percent of the population would benefit by including their genotypes for these two genes. By including the genotypes along with clinical and demographic information, initial dosing is much closer to the ideal dose, thus limiting potential adverse events."