Practice variations in biochemical screening for Down syndrome.

The American College of Obstetricians and Gynecologists has recommended that when using biochemical screening for Down syndrome, the cut-off selected for counseling the patient should be consistent with the Down syndrome risk at which the obstetrician routinely offers prenatal cytogenetic diagnosis on the basis of maternal age alone. They also state that multiple marker testing in women over the age of 35 years cannot be recommended for routine Down syndrome screening as an equivalent alternative to offering prenatal cytogenetic diagnosis. The American College of Medical Genetics has issued similar statements. We wanted to determine current practices in regard to these suggestions. A questionnaire was mailed to members of the Society of Perinatal Obstetricians asking: (1) At what maternal age do they offer counseling/amniocentesis? (2) Do they adhere to the Colleges' recommendations with regard to counseling/amniocentesis? (3) Do they change the risk for women age 35 years or over based on serum screening? Results showed that (1) Most members currently identify attaining the age of 35 years as a separate risk factor. (2) There were wide variations in the risk quoted for women 35 years old. (3) Many members used a different risk for their biochemical screening cut-off. (4) 74% of the members would increase the age-related risk for women over 35 years based on serum screening and 49% would decrease this risk based on serum screening. Among members, there were wide variations in the risks quoted; the biochemical screening cut-off used; and the use of serum screening in women over the age of 35 years.