Antenatal screening for Down's syndrome
BMJ 2004; 329 doi: https://doi.org/10.1136/bmj.329.7470.811 (Published 07 October 2004) Cite this as: BMJ 2004;329:811
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How many people will have been informed that there is a consultation
process taking place by the HUMAN GENETICS COMMISSION? (see website)
the consultation period has been extended to NOVEMBER 15 Open to all
theoretically, (when so few members of the public are aware of it)
My own concrns include 1) How are members chosen/elected
2) There are no'lay members'identified
3) If it is publicly funded why was the consultation not publicised
properly
4) why should members claim £150per day renumeration.
Competing interests:
None declared
Competing interests: No competing interests
Dear Editor,
In their interesting leading article on screening for Downs syndrome
(1), Alfirevic and Neilson give an informative account of the available
methods for detection in the first and second trimesters.
For those of us involved in the delivery of antenatal care, the
counselling of pregnant women and their partners is fraught with
difficulty – a full and informative discussion must include an explanation
of the condition (Down’s syndrome children can be mildly, moderately, or
severely disabled; some may die early, others live a long time).
The concept of false positive and false negative blood tests is
tricky and usually takes time to explain.
“OK” replies the pregnant woman, “I think I’ve grasped it, I’m going
to have a test that may miss some positive results and if it is negative
may not necessarily be accurate?”
“That’s right” you reply, knowing full well what comes next.
“So how can I be sure?”
“Well…..to be absolutely certain you can have a test that involves
removing fluid from around the baby or taking a sample of tissue.”
“OK, well I’ll have that then” she replies.
“That’s fine” you say, and taking a deep breath begin again, “but there
are risks – there is a small chance that the procedure can lead to a
miscarriage – gynaecologists usually quote 1 in 100.”
After some thought your patient decides to go for the invasive test.
“Now,” you go on, “have you thought about what you would do if the
test is positive?”
Alfirevic and Neilson rightly emphasise that the newer tests are
giving pregnant women more accurate information earlier than has been
previously possible. But we should not forget that one of the reasons for
doing this is to lessen the enormity of the termination of a more advanced
pregnancy. Whilst this may indeed make the decision easier for some, the
backdrop of eugenics or selective breeding remains, not to mention the
possibility of the miscarriage of a normal fetus. Some would say we are
killing normal babies to ensure we have fewer abnormal ones, or have I
misunderstood?
(1)Zarko Alfirevic and James P Neilson
Antenatal screening for Down's syndrome
BMJ 2004; 329: 811-812
Competing interests:
None declared
Competing interests: No competing interests
Alfirevic and Neilson ask, “.. what is the importance of establishing
top quality Down's syndrome screening programmes, relative to other
priorities in the maternity services—notably tackling inequalities and
ensuring that all women in labour have enough midwives to meet their
needs?” (1)
I would like to go further and ask what is the importance relative to
the priority of tackling the inequalities faced by people with Down`s
syndrome (and other people with learning disabilities) in current society?
The UK government has said that it is “committed to enforceable civil
rights for disabled people in order to eradicate discrimination in
society…. All public services will treat people with learning disabilities
as individuals with respect for their dignity, and challenge
discrimination on all grounds including disability. People with learning
disabilities will also receive the full protection of the law when
necessary.”(2)
The full protection of the law is currently not full enough to
protect people with Down`s syndrome before they are born. But as
employees of public services, we could all challenge the discrimination
against people with Down`s syndrome that was inherent in the setting up of
the antenatal screening programme.
People with learning disabilities face many inequalities such as
poverty, unemployment, and social exclusion, all of which have a negative
effect on their health (2) and their human rights are regularly
compromised (3). In addition, uptake rates cervical screening are
especially poor(2) (3). Should we not be tackling these inequalities
rather than developing more and more sophisticated methods of antenatal
screening for Down`s syndrome?
References
1. Alfirevic Z, Neilson JP. Antenatal screening for Down`s syndrome.
British medical Journal 2004;329:811-812
2. Department of Health. Valuing people. A new strategy for learning
disability for the 21st century. London:The Stationery Office, 2001 (Cm
5086)
3. Smith R. Medicine and the marginalised. British Medical Journal
1999; 319: 1589-90
Competing interests:
Unpaid Director and Trustee of L'Arche UK
Competing interests: No competing interests
Sir,
We read with great interest the paper by Alfirevic and Neilson, entitled
“Antenatal diagnosis for Down’s syndrome” (1). We agree with the Authors’
concerns about the difficulties of translating in a “real-world” setting
the abstract concepts of detection rate and false positive rate in the
antenatal diagnosis for Down syndrome (DS). The Authors focused on the two
main objectives for any mass screenings, that is to have a high enough
detection rate, (in order to avoid undesired DS pregnancies) and a low
enough false positive rate (in order to avoid antenatal invasive diagnoses
in healthy fetuses, carrying 1% risk of pregnancy loss).
Prenatal
diagnosis is important not only for making a decision about interruption
of the pregnancy, but also for helping those parents wishing to complete a
DS pregnancy in receiving adequate support. To this regard, it should be
underlined that the latter is fundamental to obtain the full acceptance of
a DS baby from the family, which seems to play a relevant role in giving
to these patients the opportunity to reach their full potential (2). In
particular, a preconceptional identification of couples at risk for DS
offspring would be highly advisable. Recent research from our group seems
to indicate that subtle changes in the light reflectance and microvascular
network patterns of the oral mucosa are present in the healthy parents of
DS patients (3,4). The evaluation of accuracy at this phase of the study
suggests 100% sensitivity and specificity. Although these results should
obviously be confirmed in large, unselected population recruited in a
prospective way, these findings may represent a new, non invasive,
complementary tool in the antenatal screening of DS offspring.
REFERENCES
1. Alfirevic Z, Neilson JP. Antenatal screening for Down's syndrome.
BMJ. 2004;329(7470):811-2.
2. Latini G. The joy of having a child with Down syndrome Acta Paediatr.
2002;91:1291-3.
3. Latini G, De Felice C, Parrini S, Chitano G, Verrotti A. Oral mucosa
spectrophotometric changes in healthy parents of patients with Down
syndrome. Prenat Diagn. 2004;24:685-7.
4. Latini G, Bianciardi G, Parrini S, Laurini RN, De Felice C. A new
clinical sign in Down syndrome patients and their unaffected parents.
Pediatr Res 2003;54:562
Competing interests:
None declared
Competing interests: No competing interests
Sir,
Alfirevic and Neilson are optimistic if they believe that current
screening for Down's syndrome in unborn children allows preparation for
the birth of a baby with that condition (1). A more realistic rationale
for screening was suggested by Gilbert (2) - "the main considerations for
providers of screening for Down's syndrome should be minimising the risk
of babies with Down's syndrome being missed by the test...".
Current screening programs suggest invasive karyotyping where the
risk is considered 1:250 or greater after testing maternal serum, but with
an acknowledged risk of 1% of miscarriage with amniocentesis or chorionic
villous sampling this suggests that the acceptable loss of healthy
children to avoid a baby with Down's syndrome is 2.5:1.
The SURUSS study (3) was a prospective study of 47,053 singleton
pregnancies including 101 babies with Down's syndrome. A screening test
with a false positive rate of 3% and detection rate of 75% (the target set
by the National Screening Committee by April 2007) will still have led to
over 1400 false positive results to obtain 75 true positive results, and a
loss, presumably, of 14 healthy pregnancies just to obtain the diagnosis.
The literature is further complicated by varying aims (to reduce
false positives, to reduce false negatives, to reduce costs) and varying
meaurements (of the test -sensitivity, specificity-, of the screening
program -total number of affected births, cost per affected birth
prevented-, and of the risks for a test results -positive and negative
predictive values-), few of which are empowering for pregnant women.
There should be no doubt, that while reducing false alarms and
preventing miscarriage are seen as worthwhile aims, the fundamental
purpose of screening for Down's syndrome in the National Health Service is
to prevent as many affected births as possible. All other considerations
are seen as secondary. This is both a measure of the screening program and
a measure of us.
Dr C O'Loughlin
Cambridge
1 Antenatal Screening for Down's syndrome, Alfirevic Z, Neilson J,
BMJ 2004;329:811-2
2 Screening for Down's syndrome: effects, safety and cost
effectiveness of first and second trimester strategies, Gilbret RE, Augood
C, Gupta R, Ades AE, Logan S, Sculpher M, can der Meulen JHP
3. SURUSS in perspective,Wald NJ, Rodeck C, Hackshaw AK, Rudnicka A,
Br J Obstet Gynaecol 2004;111: 521-31
Competing interests:
None declared
Competing interests: No competing interests
Why Down's Syndrome?
I am intrigued as to why Down's Syndrome, of all the potential causes
of learning disability, is chosen as the one to be tested for prenatally?
The proportion of all congenital anomalies present at birth which are
contributed to by Down's is small (although rising with average maternal
age) and the fact remains that anomalies we cannot test for are far more
important (in terms of numbers)than those we can.
I am not even convinced that screening for Down's syndrome can be
justified on the criteria that newly-initiated screening programmes have
to fulfil, i.e. population prevalence and severity, advantages to early
diagnosis, treatability if detected early and minimal harm as a result of
false positives.
I am under the impression that Down's is screened for only because it has
always been done this way, an industry has been built up around it and we
are now too far down the line to question the value of it.
Competing interests:
None declared
Competing interests: No competing interests