A small variation in a gene has been discovered to be the reason behind the treatment for hepatitis C working better for white patients than for African-American patients.

A team led by David B. Goldstein and John McHutchison, found that the coding at a single site on the DNA, out of the three billion sites in the human genome, made all the difference in people's response to the treatment. This research was conducted using the genetic test called genome-wide association study.

A special kind of interferon, known as interferon-lambda-3, has made this site close to the gene and could help in controlling the activity of the gene. In some cases the DNA unit on this site is T and in some others it is C. There are always two copies of the genome coming from each parent because of which people may have T's on both copies or C's on both copies or a T on one and a C on the other.

The study was done on 1,137 patients given standard treatment on hepatitis C. Among 80 percent of the participants this virus was terminated with this gene variant as compared to the 30 percent that who lacked this gene.

As many as 170 million people across the globe, including 3.2 million in the U. S., suffer from chronic hepatitis C, which is spread by contact with infected blood and can lead to liver cirrhosis and cancer.

This variant will be very helpful for doctors because before deciding whether to treat patients for hepatitis C, which has side effects like flu and depression, they can conduct a test for the variant.