Multiple marker screening for Down syndrome--whom should we screen?
BACKGROUND
The multiple marker test highlights the complexities of an expanding number of genetic tests that family physicians can offer to their patients. Many concerns surround the use of the multiple marker test, including a poor understanding of the test by physicians and patients, limited sensitivity, increased anxiety among women, and the risks of amniocentesis in patients who have false-positive results.


METHODS
An online search of the medical literature was used to select English-language articles addressing the burden of suffering from Down syndrome, and efficacy, cost-effectiveness, and psychological effects of screening.


CONCLUSIONS
Down syndrome occurs in 0.99 per 1000 births, and the risk increases with age. Between 10% and 20% of infants die in the first year, predominantly from heart defects. Special education, the move away from institutionalization, and more employment opportunities have improved the outlook for these persons. The multiple marker test has an overall detection rate for Down syndrome of 56% with a 7% false-positive rate. A laboratory cutoff ratio of 1:190 is the most efficient for optimizing the detection rate and minimizing the false-positive rate. Limited screening to women older than 30 years appears most cost-effective, reducing losses of normal fetuses secondary to amniocentesis and the number of pregnant patients requiring pretest counseling. The family physician needs to inform the patient of the nature, purpose, and risks of screening including the psychological effects. Pretest counseling should be nondirective.
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Central Washington Family Medicine Residency Program, Yakima 98902, USA.
Ball
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D000293:Adolescent; D000328:Adult; D000649:Amniocentesis; D003661:Decision Support Techniques; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D005315:Fetal Diseases / Q000175:diagnosis*; D006801:Humans; D011247:Pregnancy; D011296:Prenatal Diagnosis; D012680:Sensitivity and Specificity