Oncor Inc. of Gaithersburg an nounced yesterday the development of a new test for the congenital disease Down's syndrome and certain other disorders caused by genetic abnormalities that the company said is more accurate and faster than current methods.

Oncor's test can be performed during the first three months of a pregnancy, and the test results can be obtained in one day, the company said.

In contrast, amniocentesis -- a common prenatal test for such disorders -- cannot be performed until the 16th week of pregnancy, and test results take up to three weeks to report.

Richard Leavitt, director of science information for March of Dimes, said Oncor's test has "a clinical usefulness in certain situations."

He said, however, that the main problem with the Oncor test is "it is not going to give you a total picture of chromosomes."

Leavitt said that geneticists generally are not just looking for Down's syndrome but for numerous genetic disorders.

Amniocentesis allows the geneticist to look at the entire chromosome picture and detect a wide range of problems.

In contrast, the Oncor test more narrowly looks at abnormal arrangements of certain chromosomes that signify disease.

Stephen Turner, chairman and chief executive of Oncor, said the Oncor test is more accurate than amniocentesis and will cost patients less than $100, compared with a cost of $600 to $900 for amniocentesis.

Turner said Oncor expects the genetic test to develop into one of the company's major lines of business.

Oncor, which has $4 million in sales and 50 employees, also has developed other tests, including a DNA-type cancer test, and a test to detect the genetic component of the AIDS virus.