What is a screening test?
Screening is the initial test performed on urine specimens to determine the presence or absence of drugs. When a urine sample is tested with a drug present, the screening test can also establish the probable identity of the drug. The most important quality of a screening method is that it is highly sensitive to the presence of drugs for which the test is being conducted. However, highly sensitive tests tend to be less reliable at identifying exactly which drugs are being detected. For example, a screening test for amphetamines might be positive when certain commonly used decongestants are present. For this reason, it is essential to double check all positive screening results with a more specific method.
A screening test is a safe, noninvasive way to learn about the risk of having a baby with certain birth defects such as Down syndrome (trisomy 21), trisomy 18 and 13, open neural tube defects and cardiac defects. A screening test is meant to identify pregnancies at high risk, not to provide a definitive diagnosis. Amniocentesis and CVS are diagnostic tests that provide a definitive diagnosis of Down syndrome and other chromosome abnormalities. These invasive tests are associated with a risk of complications to the pregnancy. What are Integrated and Sequential screening? Integrated and Sequential screening are tests that determine whether there is increased risk of having a baby with Down syndrome, trisomy 18, or an open neural tube defect, such as spina bifida. These tests require an ultrasound with special measurements of the nuchal translucency (NT), a blood test performed in the first trimester, and another blood sample obtained in the second trimester (Afp4). What is Down syndrome?
