According to
an estimate by NHS mild pre-eclampsia affects up to 6% of pregnancies, while
1-2% of patients develop severe preeclampsia. Data Centre for Maternal and Child Enquiries
Mission statement shows pre-eclampsia, and associated eclampsia, are the second
leading cause of direct maternal deaths in the UK.
NICE have
approved and recommended two blood tests Triage PlGF test (Alere) and the
Elecsys immunoassay sFlt-1/PlGF ratio (Roche Diagnostics) to help rule-out
pre-eclampsia between 20th and 35th week of
pregnancy.
The tests detect
changes in the blood indicating that the placenta is not developing properly.
The tests
however are not meant for diagnosing preeclampsia.
The tests
were approved by NICE after the groundbreaking PROGNOSIS study results were
published in New England Journal of Medicine in January,2016.
The PROGNOSIS
study has demonstrated that low ratios of the proteins sFlt-1 and PlGF in the
blood of women at high risk of developing of preeclampsia can predict the
absence of the condition within a period of one week (the rule-out claim). The
data published today show that an sFlt-1/PlGF ratio of 38 and below can rule
out the development of preeclampsia within the next week with a very high
confidence level of 99.3%.
PROGNOSIS
was a multi-center, prospective, double-blind, non-interventional trial
evaluating the short-term prediction of preeclampsia, eclampsia and HELLP
(hemolysis, elevated liver enzymes, low platelet count) syndrome in pregnant
women with suspected preeclampsia. Sponsored by Roche, the PROGNOSIS study
aimed to address the limitations of the traditional clinical parameters used to
predict preeclampsia, and to demonstrate the utility of the Elecsys®
preeclampsia ratio test in this context.
Identifying
women who are unlikely to develop preeclampsia in the short term will save them
from the stress of monitoring and the disruption to their home life caused by a
stay in hospital.
The test is
available in all countries accepting the CE mark in Europe, Latin America,
Middle East, Africa and Asia. The test is currently not available in the United
States and Japan.
PROGNOSIS
also demonstrated that an sFlt-1/PlGF ratio greater than 38 may help predict
whether women with suspected preeclampsia will develop the condition within
four weeks (the rule-in claim), allowing doctors to identify
at-risk patients who need close monitoring.
Dr Jenny Myers, who is also Senior Lecturer
and Consultant Obstetrician, Maternal and Fetal Health Research Centre, Central
Manchester Foundation Trust said “At the moment women with suspected
pre-eclampsia often have to come into hospital for 24 to 36 hours so we can
make a diagnosis, but now, for women between 20th and 35th week
of their pregnancy, these new tests may avoid the need for admission to
hospital.”
“The tests
will be extremely valuable to help rule out pre-eclampsia before the 35th week
of pregnancy, when approximately 1/3 of women with pre-eclampsia are diagnosed.
“Doctors
will need to be clear with patients, depending on which test is used, the
result is only valid for 7 to 14 days and neither test definitively rules out
pre-eclampsia for the rest of the pregnancy.
“However
these tests represent a great stride forward in the management and treatment of
pre-eclampsia.”
The cause of
preeclampsia is not fully understood; many factors have been implicated in the
development of this life threatening disease. Recent research provides evidence
that angiogenic factors such as placental growth factor (PlGF) and soluble
fms-like tyrosine kinase-1 (sFlt-1) play a major role in the development of the
disease.
It is
postulated that preeclampsia is caused by an imbalance of angiogenic factors of
sFlt-1 (anti-angiogenic protein) and PlGF (pro-angiogenic protein). During
normal pregnancy both these proteins are involved in placental vascular remodeling.
In normal
pregnancy, PlGF levels rise and peak at 26 to 30 weeks, so when PlGF levels do
not rise during pregnancy this may be an indicator that the placenta is not
developing properly, predict subsequent development of preeclampsia.
The Elecsys
immunoassay sFlt-1/PlGF ratio also measures a protein called soluble FMS-like
tyrosine kinase-1 (sFlt-1). The protein sFlt-1 stops other proteins that help
to form blood vessels, like PlGF, from working. In pre-eclampsia if
sFlt-1levels are higher than those seen in normal pregnancy it could be an
indicator the placenta is not developing properly.
The sFlt-1/PlGF
ratio measurement in combination with proteinuria, blood pressure and Doppler ultrasound
gives better prediction of preeclampsia.
Professor Carole Longson, director of Centre for Health Technology at
NICE added “Until
now there have been no tests which doctors can use to confidently rule-out
pre-eclampsia. This has meant women with suspected pre-eclampsia often need
increased monitoring or have to stay in hospital. Apart from being
inconvenient, this can increase anxiety at what might already be a stressful
time.
“In
recommending these tests the committee highlighted the importance of making
sure laboratories explain to clinicians if a test result doesn’t rule-out
pre-eclampsia they should not automatically diagnose women with pre-eclampsia.
Instead
doctors should follow existing NICE guidelines to make such a diagnosis. This
is so that babies aren’t delivered unnecessarily early as a result of these tests.”
Two other
tests were also considered initially but later not included in the guidelines.
NICE recommends further research and trials to
be carried out using these tests in women with suspected preeclampsia.
References:
No comments:
Post a Comment