Screening tests 101Sagefemme is confused about the difference between screening tests and diagnostic tests. This is really unconscionable. How can a provider accurately counsel patients about prenatal testing if she doesn't even understand the basics? Obviously, she can't. Like most direct entry midwives, she hasn't a clue what she is talking about, and therefore spreads misinformation to others.
Her latest post, Prenatal testing is an object lesson on why direct entry midwives should be required to have far more education before anyone should consider licensing them.
The issue I have with standard prenatal testing is the myth that somehow each test that is done will ensure a healthy baby or point out any issues with a baby with special needs. The myth that each procedure (the biggest offenders - the Alphafetoprotein screen and ultrasound - which are not diagnostic, just screens) offers an accurate diagnosis of any issue - and if it's not apparent with these tests then your baby must be ok.There is so much wrong with these statements that it is difficult to know where to begin. Let's take it one sentence at a time:
"The issue I have with standard prenatal testing is the myth that somehow each test that is done will ensure a healthy baby or point out any issues with a baby with special needs."
Standard prenatal testing is made up predominantly of screening tests. Screening tests, BY DEFINITION, cannot ensure a healthy baby or point out any special needs. Screening tests do one and ONLY one thing; they identify people AT RISK for specific conditions. Screening tests, BY DEFINITION, will identify a much larger group of people than will actually have the condition at issue. Those people will then be tested with the diagnostic test which is more complicated, more inconvenient and more expensive than the screening test.
So, for example, if we want to know which babies have Down's syndrome, we could perform amniocentesis on all 4 million pregnant women each year OR we can screen women with the AFP blood test, identify the few tens of thousands that are at risk and offer those women amniocentesis. Which makes more sense: 4 million amnios or 4 million AFP blood tests followed by 40 thousand amnios? Obviously, performing the blood test and limiting the numbers of amniocentesis makes more sense from the point of view of safety, convenience and expense.
"The myth that each procedure (the biggest offenders - the Alphafetoprotein screen and ultrasound - which are not diagnostic, just screens) offers an accurate diagnosis of any issue - and if it's not apparent with these tests then your baby must be ok."
Wrong again. By definition, any test which is not a diagnostic test CANNOT provide a diagnosis. This appears to be news to Sagefemme, but it is statistics 101. EVERY screening test has a false positive rate and identifies women AT RISK who do not actually have the diagnosis. Every screening test has a false negative rate, which means that a certain percentage of people identified as not at risk actually have the disease or condition. If you read the consent forms for AFP tests for example, they specifically state that there is a chance that the test will fail to identify a certain percentage of babies with Down's syndrome. That is the nature of screening tests. If you want to be sure that your baby does not have Down's syndrome, you MUST have an amniocentesis (the diagnostic test).
"Current evidence shows us that the Alphafetoprotein test, routine ultrasound and the glucose tolerance test all have rather large errors in assisting with an accurate diagnosis."
Yes, they were DESIGNED to work in exactly this way. They have a known (and deliberately high) false positive rate and a known false negative rate. They cannot make a diagnosis because they are not diagnostic tests.
"If we're really looking at empowering women with knowledge the accuracy rate, along with what the test is screening for and what the path is if an abnormal result is found, should be discussed prior to the test."
Yes, Sagefemme, but how is a direct entry midwife going to do that when she herself doesn't understand the test?
"My issue isn't with the testing alone, but the inability of the medical model to offer full disclosure about testing and it's accuracy."
No, it is DEMs who can't offer full disclosure about testing and its accuracy because they don't understand it. This is what I mean when I say that DEMs are grossly undereducated.
"For what it's worth, each of my clients receive full informed choice about Chorionic Villus Sampling, Amniocentesis, Ultrasound, AFP Screening, the Glucose Tolerance Test, Group Beta Strep Testing"
No, Sagefemme, they couldn't, because you clearly don't understand prenatal testing, the difference between screening tests and diagnostic tests, false positive rates, false negative rates and other basic concepts in testing. If you don't understand it, you can't offer accurate counseling. That's a very serious problem.
Informed choice and full disclosure should be the standard in maternity care. We also owe it to women to have an understanding about the impact of prenatal testing on the feelings towards their pregnancy, towards their baby and the choices made along the way.I agree, that should be the standard. Sagefemme, you are ethically and legally obligated to educate YOURSELF on the basics of prenatal testing so you can offer accurate information. Until now, you have been offering misinformation.