Pre-eclampsia is a potentially deadly complication of pregnancy that is dangerous both to the mother and the child. There is no way to prevent it and treatment usually involves injection of Magnesium Sulfate and the early provocation of birth. Early detection – before any symptoms become evident, can save thousands of lives – but what are the potential costs?
As reported by Reuters, an international team of researchers reported Monday that they had found a group of 45 metabolic markers that has a 90% success rate in predicting pre-eclampsia. Pre-eclampsia is a badly-understood complication in pregnancy that is characterized by hypertension and excessive proteine in the urine, and occasionally low platelet counts and liver dysfunction. It complicates 5 to 7 % of otherwise healthy pregnancies. 5% of all untreated pre-eclampsia patients develop eclampsia, which can be fatal .
The researchers compared the blood of 60 women who later developed pre-eclampsia with that of 60 women who did not. They found 45 metabolic markers that were different between the two groups of women. The test worked on 90% of the women who did develop pre-eclampsia (~54 out of 60 women) and have a false positive result in 24% of the women who did not develop the condition (~14 out of 60 women).
Out of 1000 pregnant women, between 50 and 70 will develop this complication – through no fault of their own. Of these, between 45 and 63 would be detected and could benefit from extra monitoring and/or early treatment. However, out of the 930 to 950 women that would not develop the complication, between 223 and 228 women would get a false positive result – i.e. they would be told they have a high chance of developing pre-eclampsia but would not develop it. So in a group of 1000 women, between 268 and 291 women would be told they have a high chance of developing pre-eclampsia. These women would have a chance of between 15% and 24% to develop the complication.
This means that while between 5% and 7% of women would develop pre-eclampsia, between 27% and 29% of the women will be told they have a good chance of developing the complication – which can potentially be fatal. The question now becomes: what will happen to those women? How many of those women will receive “pre-emptive” treatment for pre-eclampsia, how many will be needlessly stressed and how many will, because of that stress, miscarriage or opt for an abortion – an understandable option as pre-eclampsia is potentially lethal to both the mother and the child?
The most common treatment for pre-eclampsia involves injections with Magnesium Sulfate: it is cost effective, especially in low-GNI countries, and it is widely known as an effective way of preventing the premature birth of a child in a complicated pregnancy. It has various side effects, though.
This is my worry: the press has gotten a hold of this “breakthrough” and might cause undue pressure on a normally careful (and slow) process. A sample of 120 women is very small and, as far as I know (I haven’t found the actual publication yet) it may not be very representative ethnically. The worst thing that could happen now is for some women’s rights advocacy group to take a hold of this and, with all the right intentions, try to hasten the process of getting these tests in the field.
What I have tried to show here is that the chances of finding the right women to target for preventative treatment and extra monitoring will be difficult, even with this tool. Predicting 90% of positives may look very good, and falsely predicting 24% of negatives might not seem so bad, but with only a 5% occurrence rate that means a large part of pregnant women – more than one in five – will be targeted and most of those women – more than four out of five – wrongly. Not only will this unnecessarily stress the women in question and put an extra burden on the health system, it may also, eventually, cost lives.