One of the routine no-risk, no-questions-asked tests I had when I was early on in pregnancy was called an AFP (alphafetoprotein) test. This is a test carried out on a maternal blood sample which measures alphafetoprotein levels and three other indicators, with a view to getting an idea of the risk of Down’s syndrome. The point of the test is to assess whether or not it is worth considering an invasive diagnostic test, that is, amniocentesis.
According to this study, based on a sample of 46,193 pregnant women:
- 88 women were carrying babies with Down’s syndrome.
- 71 of those women had a positive AFP test, and 62 went on to have amniocentesis with 59 mothers subsequently choosing to abort.
- 17 of the Downs pregnancies had a negative AFP test.
- 20 children were born with Downs.
- The study does not say what happened to the “missing” 9 children, who were neither born with Downs nor aborted following a diagnosis; I suppose we must assume that 9 pregnancies aborted spontaneously.
This makes the AFP test seem like a relatively useful screening method. The chance of a false negative is 19%, but the test did pick up 81% of Downs cases.
However, there are some other really important points about this test.
The test gives you a positive if the computer says your risk of Downs is 1 in 300 or worse. This means that there is a very high chance of a false positive, that is a positive AFP test in a case where the baby does not have Downs. In the study sample, there were 3,200 false positives, which was 98% of all positive results. 7% of all women – one in 14 – given the AFP test had a false positive.
What’s the problem with a false positive?
Firstly, once you get the results, you immediately face a decision whether to proceed to amniocentesis. Amniocentesis is a procedure with a number of risks, including that it can cause miscarriage. There is generally thought to be about a 1% chance of the procedure leading to miscarriage – see this review for an assessment of the studies done. The real risk depends on other factors, usually beyond the control of the mother, such as the level of experience of the person carrying out the procedure (see this summary of evidence). Other risks include damage to the baby, particularly limb defects, and maternal infection which can even cause death.
(NB The only risk referred to in the NHS patient guide is the risk of miscarriage.)
A positive AFP test exerts considerable pressure on a woman to go ahead with amniocentesis, with all its attendant risks. The idea that 7% of all pregnant women should be routinely subjected to this pressure on the strength of a false positive is, frankly, shocking.
43% of women at the lower-risk end of the AFP-positive scale underwent the procedure, and 74% of women at the higher-risk end did so. No figures are given for the numbers of women who lost their babies because they went on to have the invasive test following a false positive. If we assume that at least half of the 3,200 affected women had the test, and 1% of those had a miscarriage as a result, then we are talking about at least 16 healthy babies lost unnecessarily, as a result of these false positives.
No figures are given for the number of women (if any) with a negative AFP test who went on to have amniocentesis as well, but I imagine that very few if any would have been encouraged to do so. It is only those with a positive result who are at all likely to be pressured into amniocentesis, even though there is a 98% chance that the positive result is a false one.
Another problem with amniocentesis is that it will not normally be done until 15 or 16 weeks, because if done earlier the risk of miscarriage is significantly greater. The results can take up to three weeks to come back, so a woman could have got to 19 weeks or later before she discovers whether or not her baby has Downs.
By now, she will very likely have felt her baby move, she will have heard its heart beat, seen it on at least one ultrasound scan, probably more. And all this time, for several weeks (ever since the positive AFP test) she will have been wondering – “Is my baby defective?” “Can I keep it?” “Should I let myself love this child?” “Should I even let myself think of this foetus as a child, as anything more than an alien *thing*?” Her whole being will be taken up, for weeks, with an internal struggle about what to do if the diagnosis is positive.
And if she chooses not to proceed to amniocentesis, that internal struggle will go on not just for weeks but for months. For months she will be wondering, “Will my baby be normal?” She will be alternatively reassuring herself that it’s only a 2% risk and beating herself about the head and heart with the fear: “What if…?”
Those are the problems with a false positive.
They are real, serious problems and risks – pressure to undergo a risky procedure, miscarriage directly caused by that procedure and, perhaps most importantly (because it is universal), real and significant emotional harm and distress.
When I was asked whether I wanted the AFP test, I was not told any of this. I was informed, as I remember, that the test would give me a risk rating for Downs, but not a diagnosis and that if necessary further tests could be carried out to make a diagnosis.
I was not told that the AFP gave a positive result for as little as a 1 in 300 risk. I was not told that 7% of women get a false positive, that 98% of positive results are false positives, or that the test only picks up 81% of Downs cases anyway. I was not told of the emotionally charged situation in which I would find myself if the test did give a positive result. I was not told that the “further tests” that might be considered if the test was positive were themselves risky or that the decision whether to have those tests would be such a difficult one to make.
In short, I was not given anything like enough information to make an informed choice about whether to have the AFP test. I was not told, and it never occurred to me to ask, because the test was presented as just one more standard, routine, everyday check that all women go through. It was never suggested that I or anyone else might ever have any reason to do anything other than tick the consent box. I ticked the box.
(Thank heavens, in my case, the AFP test was negative and I didn’t give it a second thought, any more than I did any of the other tests that were done on the various samples I gave that day.)
I suppose this is just one more way in which the healthcare system disempowers pregnant women. We are denied the information we need to make informed choices at every turn. We are encouraged to rely entirely on the advice of the health professionals. Despite much talk of “informed consent” and “choice”, we are denied any real choice because decisions are presented to us as easy and obvious and only those who already know different will ever feel able to resist.
So this is just one more example of that systemic failing. One more example of women being treated as children – infantilised – by a system that has already decided what is best for them and assumes their agreement without making any genuine effort to engage them in the decision.
And it is also, I think, an example of a systemic failure to take emotional harm seriously. It is evidently considered acceptable to expose women to the emotional harm and distress of a false positive without prior warning, discussion or counselling.