Diagnosis of Down's Syndrome Can be More Precise Now

Scientists have developed a non-invasive method for diagnosing Down's Syndrome-a genetic disorder that is caused by the presence of all or part of an extra 21st chromosome in the foetus.

The method, named relative chromosome dosage (rcd), examines nucleic acids (that contains genetic materials) of the foetus present in mother's blood. It scores over traditional non-invasive diagnostic methods such as ultrasound in terms of accuracy.

Using maternal plasma for genetic studies of the foetus has been difficult till now because the sample contains nucleic acids of both the foetus and the mother. A group of Hong Kong-based scientists have solved this puzzle by basing their method on the total nucleic acid in the sample which easily shows if an extra dose of chromosome 21 is present in it.

Traditional non-invasive methods look at external indications of genetic abnormality. For example, through ultrasound, doctors look at the excessive accumulation of fluid in the foetus' neck to diagnose Downs' Syndrome. But such methods often get influenced by the gestation period and may give inaccurate results. The new method is likely to be more accurate as it directly looks at chromosomes. The study was published in the journal of the Proceedings of the National Academy of Sciences of the United States (Vol. 104, No. 32).

Source: Down to Earth, September 2007