Re: Thrombophilia and preeclampsia
We thank everyone for highlighting an ambiguity in our guideline(1)
with regard to the presence of antiphospholipid antibodies. We would like
to reassure readers that it was never our intention to imply or recommend
that women be routinely tested for the presence of lupus anticoagulant or
anticardiolipin antibodies at booking. We agree that the false positive
rate is high and that the prevalence of these antibodies in the general
obstetric population is about 2%, much higher than the prevalence of
antiphospholipid syndrome (APS). Although the papers on which the relative
risk calculation was based did screen all women at <_9 weeks="weeks" booking="booking" and="and" not="not" just="just" those="those" with="with" features="features" of="of" aps="aps" we="we" believe="believe" that="that" routine="routine" screening="screening" for="for" is="is" indicated="indicated" until="until" the="the" results="results" intervention="intervention" studies="studies" health="health" economics="economics" assessment="assessment" ie="ie" cost="cost" effectiveness="effectiveness" are="are" available.="available." p="p"/> However if it is already known that these antibodies are present (on
more than one occasion six weeks apart) then this should be considered a
risk factor. Screening for the presence of these antibodies would only be
warranted if there are clinical features consistent with the
antiphospholipid syndrome2 that is
· 3 or more consecutive miscarriages (<10 weeks)
· One or more fetal death (> 10 weeks)
· One or more premature birth (<34 weeks) due to severe pre-eclampsia or placental insufficiency
The association of pre-eclampsia with inherited thrombophilia was not considered in the systematic review of Duckitt and Harrington3 and therefore known genetic thrombophilia was not included in the risk factors identifiable at booking. However we do agree with Dr Shojai that evidence is accumulating for a significant association between the presence of inherited thrombophilia and an increased risk of pre-eclampsia and this will be considered when the guideline is updated.
1. Milne F,Redman C,Walker J,et al.The pre-eclampsia community guideline (PRECOG): how to screen for and detect onset of pre-eclampsia in the community.BMJ 2005; 330: 576-580
2. Wilson WA, Gharavi AE, Koike T, Khamastha MA. International consensus statement on preliminary classification criteria for antiphospholipid syndrome: Report of an International workshop Arthritis Rheum 1999; 42, 1309-11.
3. Duckitt K, Harrington D. Risk factors for pre-eclampsia at antenatal booking: a systematic review of controlled studies. BMJ 2005;330: 565-7.
Competing interests: None declared
Competing interests: No competing interests