Serum screening for Down's syndrome: experiences of obstetricians in England and WalesBMJ 1994; 309 doi: https://doi.org/10.1136/bmj.309.6957.769 (Published 24 September 1994) Cite this as: BMJ 1994;309:769
- J M Green
- Accepted 18 July 1994
Objectives: To assess the experiences of obstetricians in England and Wales of serum screening for Down's syndrome.
Design: Postal questionnaire survey.
Subjects: Questionnaires were sent to all practising obstetricians in England and Wales with non-academic20appointments who had not participated in an earlier (randomly sampled) survey of obstetricians' attitudes (n=555). Responses were received from 393 (71%), of which 351 were analysed. The data represent about one third of obstetric consultants in England and Wales.
Main outcome measures: The extent of use of serum screening for Down's syndrome, and the problems encountered.
Results: Serum screening for Down's syndrome was being offered on some basis by virtually all obstetricians in the survey. Nearly half the sample said that they did not have adequate resources for counselling all the women to whom screening was offered. Many problems were reported, which in all cases were more common than equivalent problems encountered with serum screening for neural tube defects. Over 80% (289) said that women not understanding the test was a problem.
Conclusions: There is considerable confusion associated with serum screening for Down's syndrome. The precedent of serum screening for neural tube defects does not seem to have lessened the problems experienced, rather the contrary. Many obstetricians report inadequate resources for counselling, which is consistent with the high prevalence of problems associated with women not understanding the test. There is an urgent need to consider what counselling should consist of and who should undertake it and to ensure that necessary resources are available.
Serum screening for Down's syndrome is now widely used in England and Wales
More problems are being reported than was the case with serum screening for neural tube defects
Obstetricians do not think that they have the resources to provide adequate counselling; 81% cited “women not understanding the test” as a problem
There is an urgent need to consider what counselling should consist of and who should undertake it and to ensure that necessary resources are available
Screening for fetal abnormality has become a major part of antenatal care, and there has been much discussion of the pros and cons of various tests - notably, serum screening for Down's syndrome. A survey in 1991 found that the use of such screening in the United Kingdom was expanding rapidly but in a piecemeal and sometimes inappropriate fashion.1 This survey was based on returns from directors of public health and asked about provision in 1991 and expected provision in 1992. Debates in the medical press suggest that many of those at the front of service provision are unhappy about the test, but there is no systematic information about the attitudes and experiences of obstetricians on this subject.
I carried out a survey of the attitude of consultant obstetricians towards prenatal screening and diagnosis and towards termination of pregnancy. I report here on the questions relating to serum screening for Down's syndrome. Other aspects of the survey have been reported elsewhere2 and are being prepared for publication.
Subjects and methods
Names and addresses of members and fellows in England and Wales were obtained from the Royal College of Obstetricians and Gynaecologists. Subjects were excluded from the survey if they were known to have retired; work in a specialty other than obstetrics (for example, genitourinary medicine); have an academic appointment (which excluded about 10%); or have taken part in another recent survey of obstetricians' attitudes. Questionnaires were sent to the remaining 555 obstetricians in May 1993 (appendix). Reminders were sent at the beginning of June and again at the beginning of July. Overall, 393 responded (71%). Five indicated that they did not want to take part and 27 that they were not practising obstetricians. Four questionnaires arrived too late for inclusion. Analysis is therefore based on 357 (64%) questionnaires, although inevitably some questions were omitted by some respondents. This number represents about a third of consultant obstetricians in England and Wales.
Most (335; 94%) of the consultants offered some form of serum screening for Down's syndrome to at least a specified subgroup of their patients. Over half (184) were offering it to all women in their care (table). Of these, 176 were also using serum to screen for neural tube defects. Those offering serum screening for Down's syndrome to only some of the women in their care, however, were less likely to use it in this way: 34 out of 143 (24%) of them said that no woman in their care was offered serum testing for neural tube defects. Only 14 respondents who were offering serum screening for neural tube defects were not offering serum screening for Down's syndrome to any women in their care, and only eight respondents offered no form of serum screening to any of their patients. Of those offering serum screening for Down's syndrome to all women, 156 (85%) said that all women received a dating scan, although when the scan was offered is unknown.
One hundred and twenty three respondents (35%) indicated that they were carrying out certain procedures because of outside pressures rather than because they consider them clinically valuable. Serum screening for Down's syndrome was the most commonly specified (67 (19% of the sample, 54% of those answering yes)). Seven of those giving this response were not currently offering the test but were presumably indicating that they felt under pressure to do so. Of those offering serum screening for Down's syndrome to some women, 33 out of 138 (24%) gave this response, as did 24 of the 179 (13%) who offered it to all women.
A similar number of respondents (119; 33%) indicated that outside pressures prevented them from implementing certain procedures that they considered to be beneficial. Again, serum screening for Down's syndrome was the most commonly specified (67 (19% of the total sample; 56% of those answering yes)). Eight of the 22 (36%) obstetricians who did not perform serum screening for Down's syndrome would like to be doing so. Of the 184 already offering Down's serum screening to all women in their care, 10 (5%) also gave this answer, indicating that they wanted to be providing a better test - for example, triple test instead of test for (alpha) fetoprotein alone or first trimester scan.
Of the 315 offering some serum screening, 146 (46%) said that they did not have sufficient resources to provide adequate counselling, and this was clearly a source of concern to many. “If you can't provide adequate counselling, you shouldn't be doing the test! It's all part of one process.” When asked the same question with regard to counselling for amniocentesis and chorionic villus sampling only 107 (30%) said that their resources were inadequate.
For every one of a list of potential problems associated with serum screening (see appendix), screening for Down's serum was reported to be more of a problem than serum screening for neural tube defects (sign test, P<0.01 or less in all cases).
The most frequently encountered problem for both conditions was anxiety caused by false positive results (266/302 (88%) for Down's 238/309 (77%) for neural tube defects). This observation is also supported by some studies that have measured anxiety in women undergoing these tests.3 One hundred and ninety nine out of 296 (67%) thought that the offer of the test created anxiety for at least some women (129/309 (42%) for neural tube defects). Women's understanding of the test was seen as a problem in Down's screening by 245 out of 301 (81%) respondents and midwives' understanding by 151 out of 300 (50%). Clearly these are likely to be related problems. One respondent also added doctors not understanding the test as an additional problem.
Serum screening for Down's syndrome is being offered on some basis by virtually all obstetricians in England and Wales, with about one half offering the test routinely to all women in their care. My questionnaire did not ask which biochemical test was being used or the basis for defining a subgroup to whom to offer the test. Comments suggest problems in both of these areas. Wald et al found that several districts were offering serum screening only to older women as an alternative to amniocentesis,1 and this was also evident in my survey. For some obstetricians this was a non-clinical decision: “The triple test is offered to women of 35 and over, but this is because of other factors within the administration.” For others it was reasoned policy: “We have taken a policy decision as a unit not to offer a screening service for Down's to the whole population, only to those who request and those aged 35-37 who prefer not to opt directly for amnio. This is because of the 60% detect rate <37 years and 80% >37 years which we feel misses too many cases.”
There were also difficulties integrating serum screening for Down's syndrome with scanning: “False positive Down's anxiety would be less if we could take on first trimester scans.” Another respondent said: “Scan restrictions (financial constraint) mean routine dating and anomaly scan are combined at 18 weeks, so serum screening is not undertaken until after this.”
Other comments highlighted the complexities associated with the decision to offer screening; some obstetricians thought that they had a negligible input to the decision, others felt overwhelmed by the choices about which markers to measure and to which women to offer the test. A number commented on the need for a national policy.
Serum screening for Down's syndrome was seen as consistently more problematic than serum screening for neural tube defects. Why should this be? Firstly, the test is replacing two existing tests: serum screening for neural tube defects and age as a screening test for Down's syndrome. The test procedure is the same as for neural tube defects so women may mistakenly think that they understand.4 The relation between age and Down's syndrome has been accepted by women and midwives but is not recognised as screening, and thus most older women (those whose babies do not have Down's syndrome) were not being seen as “false positives,” just as the young women who gave birth to Down's babies were not seen as “false negatives.” The introduction of a new screening method has challenged old ideas by drawing attention to the fact that any pregnant woman could be carrying a fetus with Down's syndrome.
Difficulties in understanding the test arise partly because details (what is measured and what cut off points are used) vary from place to place. A more fundamental difficulty, however, is a failure to distinguish between screening and diagnosis. The test is seen as poor because it has false positive and false negative results; one obstetrician commented that if the pick up rate was only going to be 57% rather than 66% “why not toss a coin?.” In fact the triple test performs relatively well on these criteria with a positive predictive value of 1 in 68, which is about twice that of maternal age.
Nearly half of those offering serum screening said that they did not have adequate facilities to counsel the women to whom the test is offered. This is an issue raised by the recent report from the Nuffield Council on Bioethics Genetic Screening: Ethical Issues.5 There are clearly questions about who should counsel, where and when, and what counselling actually means. Should information about the test be given by the hospital or the primary care team? This is an issue in need of resolution given the current trend towards returning antental care to the community. Women may turn to their general practitioners and community midwives for information and support but find that knowledge is lacking.4
There are different requirements for counselling before and after tests. Pretest counselling should give women the information on which to decide whether or not to be screened.6 This may include consideration about how they might react to certain scenarios - for example, a positive result of screening or amniocentesis - but does not involve many of the emotional and therapeutic ingredients which are often associated with the word “counselling” in other contexts and which may be needed after positive test results. Clarification of terminology and of the relative roles of obstetricians and the primary care team may help to ensure that women receive the counselling that they require, which is not currently the norm.4, 7
This survey was funded by a fellowship awarded by the Institute for Social Studies in Medical Care.
Selected items from questionnaire
2 For each of the following screening tests please say whether it is routinely offered to: (1) all pregnant women in your care (assuming that they book in time), (2) a defined subgroup, or (3) none?
3 Some obstericians find themselves carrying out certain procedures because of outside pressures - for example, consumer demand, medicolegal concerns, management decisions - rather than because they consider them clinically valuable. Is this true in your case for any of the screening/diagnostic procedures that you offer?
Yes … 1 No … 2
If yes, which?
4 Some obstetricians find that they are unable to carry out certain procedures that they think are beneficial because of outside pressures - for example, management decisions, financial constraints. Are there screening/diagnostic policies that you would like to implement but cannot?
Yes … 1 No … 2
If yes, what procedures and why?
8 Do you have sufficient resources to provide adequate counselling for all patients who are offered serum screening?
Yes … 1 No … 2
IF YOU DO NOT OFFER SERUM SCREENING FOR DOWN'S SYNDROME, PLEASE GO TO QUESTION 10
9 If you do offer serum screening for Down's syndrome could you please indicate the extent to which you have encountered any of the following problems?
IF YOU DO NOT OFFER SERUM SCREENING FOR NEURAL TUBE DEFECTS, PLEASE GO TO QUESTION 11
10 If you do offer serum screening for neural tube defects, could you please indicate the extent to which you have encountered any of the following problems.
Is there anything else that you would like to say about serum screening?
15 Do you have sufficient resources to provide adequate counselling for all patients who are offered amniocentesis/chorionic villus sampling?
Yes 1 No 2