In practical terms, what does the screen positive rate mean?
The screen positive rate is the chance that a test will be above the screen cut-off and the result will be reported as screen positive. This rate includes both false positives and true positives. A false positive means that the screen is positive but the baby is unaffected whereas a true positive means that the pregnancy screens positive and the baby is affected. The screen positive rate varies for the different tests and for women of different ages. However, for all tests and all age groups, the majority of women who screen positive have an unaffected pregnancy. For example, women less than 35 years of age, who choose SIPS, have a 3.7% chance of having a screen positive result. Of those women who screen positive, 97% of them will have an unaffected pregnancy. These women have a false positive screen result.
