Principles practicalities of carrier screening: attitudes

J Med Genet 1992; 29: 313-319

Principles and practicalities of carrier screening:attitudes of recent parents

Josephine M Green

AbstractPopulation carrier screening for cysticfibrosis could soon be a reality, but weknow very little about people's attitudestowards genetic disease in general or cys-tic fibrosis in particular. This paper re-ports a study which aimed to investigatesome of these attitudes and also toexplore feelings about CF carrier screen-ing given its practical limitations. Theresults are discussed in the context ofearlier studies which have not raisedthese practical issues.

Child Care andDevelopment Group,University ofCambridge, FreeSchool Lane,Cambridge CB2 3RF.J M Green

Received 26 July 1991.Accepted 28 August 1991.

With the identification of the cystic fibrosis(CF) gene,'2 population carrier detection is apractical possibility and three pilot studiesfunded by the Cystic Fibrosis Trust arealready under way in the UK. The intention ofoffering such screening to a general populationis to inform people of their carrier risk beforethey give birth to an affected child. This marksa major departure from previous practice inpreventive medicine; we have no precedent forscreening of this kind in the UK. Although itmight be argued that screening programmesfor sickle cell conditions, thalassaemia, andTay-Sachs disease are comparable becausethey are also autosomal recessive disorders,their occurrence in the UK is mostly restrictedto ethnic minority groups, and therefore offersno model for mass screening of the populationas a whole. Furthermore, even for these con-

ditions, it is apparent that generalisation is notpossible from one disease to another orbetween different cultural contexts (for in-stance, compare the examples of thalassae-mia in Cyprus3 or London4 with the state ofsickle cell screening in the UK5).We need to know how the population will

react to the existence of carrier screening forCF and, arguably, the best way of finding outis to try it and see. From the pilot programmesthat are already operating we will discoverwhat percentage of people accept the offer ofcarrier screening and, it is to be hoped, we willalso learn something about the best way tooffer it. For example, whether to use buccalscrapings or blood samples, to test at GPsurgeries or in antenatal clinics, and whetherto invite people to attend for screening or totest opportunistically.However, there are important questions to

be asked that might not be answered by this'try it and see' approach. These concernunderlying attitudes towards genetic disease ingeneral and CF in particular. For example,should screening be compulsory? Is it believedthat people have a social responsibility to avoidthe birth of handicapped children? What

priority should screening for genetic diseasehave in NHS budgeting? Are people con-cerned about possible misuse of geneticinformation? Such questions could, in prin-ciple, be asked of people to whom screening isbeing offered. However, there is a danger thatanswers would be biased by a need for cognit-ive consistency on the part of respondents.6Those accepting testing might feel a need to bepositive about screening, while those declin-ing, even if only for pragmatic reasons (such asinconvenient clinic times), might play downthe advantages of screening. Arguably, thebest way to obtain information about underly-ing attitudes is to separate these questionsfrom the practicalities of testing, and to askthem of people who are not being offeredscreening at that time.Another reason for taking this latter ap-

proach lies in the particular uncertainties ofCF screening, especially the uncertain pro-gnosis and the fact that, at best, the test willdetect only 85% of carriers. These are featureswhich may be important in people's decisionmaking. Somebody may support the idea ofgenetic carrier screening for some conditionsbut not consider the severity ofhandicap in CFsufficient grounds for avoiding the birth of anaffected child. Or, they may want screeningbecause they want the reassurance of knowingthat they are not a carrier, in which case theymay feel that 85% sensitivity is not goodenough. In order to assess these issues, it isnecessary first to raise general questions aboutgenetic screening, free from real life practical-ities, and then to introduce these considera-tions subsequently.This paper reports a small scale study which

examined attitudes towards genetic screeningusing this approach.

MethodsQuestionnaires were sent to 207 couples whohad recently taken part in another question-naire based study being carried out by ourteam. This earlier study was of attitudes andexperiences concerning prenatal screening7and the women had filled in questionnaires atthree points in pregnancy and at six weeksafter delivery. Their partners had not beendirectly involved in the earlier study, althougha number had commented that they wouldhave liked to have had questionnaires of theirown to fill in. The women had originally beenrecruited through nine District General Hos-pitals, all within 60 miles of Cambridge, whenthey had registered for antenatal care. At thetime when questionnaires were sent for thepresent study, their babies were between 2 and5 months old. The questionnaire was not sent

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if any of the following applied: (1) neonataldeath or congenital abnormality in the mostrecent pregnancy, (2) major maternal healthproblems since delivery (including depres-sion), (3) no current partner, (4) reports of apoor relationship with partner, (5) not intend-ing to have more children, (6) scored less than3 on a scale from 0 to 5 in answer to thequestion "Have you enjoyed taking part in thisresearch?" (0 meaning not at all, 5 meaningvery much). This last question came at the endof the questionnaire that was completed sixweeks after delivery, and the purpose of theexclusion was to avoid imposing on peoplewho were unlikely to want to participate.

Because of their participation in the earlierstudy we had a considerable amount of in-formation about the women, including theirreproductive histories, attitudes to prenatalscreening, attitudes to abortion, personalknowledge of various handicapping con-ditions, and background information such asage, occupation, and religion. We also hadthese last three items for the men.

RESPONSEQuestionnaires were returned by 104 womenand 71 men (50% and 34%). These are lowerresponse rates than we would have expectedconsidering the 'track record' of the womentargetted. Although we cannot know the pre-cise reasons for non-response, we are able tocompare responders and non-responders interms of our pre-existing information aboutthem. This shows that responders tended to beolder, better educated, and to have higherstatus jobs than non-responders. There wereno significant differences between respondersand non-responders in terms of their religionor attitudes to abortion. One couple (res-ponders), out of the 207 targetted, had had aprevious child who was handicapped; two(both non-responders) had had previous chil-dren who had died.

KNOWLEDGE OF HANDICAPPING DISORDERSIn the original study women had been asked tosay which of a list of handicapping disordersthey had heard of. Responses, based on 1607women in the original study, are given in thetable. The table shows that the vast majority ofwomen had at least heard of most of thedisorders listed. Ninety-two percent said thatthey had heard of cystic fibrosis, which is ahigher figure than other studies havereported.8 Responders were somewhat morelikely than non-responders to have heard ofthe disorders, but, since most of the targetgroup had heard of them, this difference is notsignificant.

THE QUESTIONNAIREThe aim was to produce a questionnaire thatcould be read and understood by ordinarypeople with no special knowledge of genetics.In order to do this we found that we also hadto produce a short information leaflet which

Percentage of pregnant women who had heard of each ofthe following disorders at approximately 10 to 12 weeks(n= 1607).

No %

Down's syndrome 1591 99Spina bifida 1579 98Cystic fibrosis 1484 92Muscular dystrophy 1474 92Cerebral palsy 1470 91Haemophilia 1419 88Sickle cell disease 839 52Anencephaly 243 15Tay-Sachs disease 123 8

defined some of the main concepts, and parti-cipants were asked to read this before attempt-ing to answer the questionnaire. Within thequestionnaire itself the intention was to startwith basic attitudinal questions about the prin-ciples of carrier screening and to move on tomore specific scenarios. The questions aregiven in full in the results section along withthe responses given.

ResultsIn the first question we postulated a situationdesigned to elicit attitudes to carrier screeningshorn of practical problems such as the test'ssensitivity.

Question 1. Suppose that there were a test thatcould identify carriers for a serious disease thatcaused children to be born with severe phys-ical and mental handicaps. The test itselfwould be quite straightforward and 100% ac-curate. How do you think that that test shouldbe made available? (Please tick only one box.)

No %

Everyone should have to haveitEveryone should be given itunless they objectEveryone should be told aboutit and left to decide forthemselves whether or not tohave itIt should only be available inexceptional cases, for examplewhere there is a family historyIt should not be available at allDon't know

17 10

54 31

102 58

2 1

1 1

Total 175(Percentages do not total 100 owing to round-ing.)

It will be seen that most respondents see thedecision about carrier screening as one thatpeople should make for themselves. Neverthe-less, nearly one-third of the sample thoughtthat the onus should be on people to object ifthey did not want to be screened, and 15% ofthe men (though only 6% of the women)thought that testing should be compulsory.The next two questions listed a number of

advantages and disadvantages of carrierscreening and asked respondents to rate eachon a scale of importance from 0 to 3. Theadvantage of this format is that it allows people

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Principles and practicalities of carrier screening: attitudes of recent parents

to express both positive and negative attitudeswithout forcing them to make judgementsabout relative importance.

Question 2. There is still a lot of debate aboutwhether or not it is a good idea to have carrierscreening programmes. Here are some of thereasons put forward in favour. For each one,please circle a number to indicate how import-ant a reason you think it is, from 0 if you don'tthink that it is at all important, to 3 ifyou thinkthat it is very important. Circle '?' if you don'tknow.

Not Veryimpor- impor- Don'ttant tant know0 1 2 3 ?

Parents could be sparedthe trauma of having a

handicapped childNo 1 8 35% 1 5 20

The state could be savedthe costs of handicappedchildren

People couthat they

People havythings a1

Children h.be born N

Question 3have been 1ing prograrnumber toyou think itis at all imjvery impor

It would w

You shouwith natu

People whothey are enot undeitheir ownaffected

12873

32

People who were told thatthey were not carriersmight not understand allthe implications of thatresult

No 44 70 36% 25 40 21

The wrong people mightget hold of theinformation and use it todiscriminate againstcarriers

No 42 33 42% 24 19 24

The programme would useup NHS resources thatwould be better usedelsewhere

No 87 52% 50 30

It could lead to an increasein the number ofabortions (of affectedfetuses)

2112

14 118 6

49 928 5

3 122 7

No 60 41 37 26 11% 34 23 21 15 6

No 75 49 31 18 2 It is immediately apparent that this sampleNo 43 28 18 10 2 is unimpressed by cost based arguments. "The

programme would use up NHS resources thatLid be reassured would be better used elsewhere" is dismissed

No 2 16 40 116 1 by over three-quarters of the sample as beingNo 2 16 40 116 1 of little importance. Overall the advantages of% 1 9 23 66 1screening are rated as more important than thee~ ~ ~ ~~~~ ~cenn ar rated asmoekmoratohnwhe a right to know disadvantages. Excepting the cost arguments,

No 6 17 37 115 - all the advantages listed attracted a mean rat-No 3 10 21 66 - ing of 2 or more, while, with one exception, all%ve 310ght21t66odisadvantages were given a mean rating of lessive a right not to than 1. The exception was "The wrong people

wvith a handicapNo 15 5 28 104 23 might get hold of the information and use it to% 9 3 16 59 13 discriminate against carriers". Here there wasa wide spread of opinion, with men tending to

see it as more important than women.Here are some of the reasons that Generally, men and women had fairly similar

put forward against having screen- patterns of ratings, although more womennnmes. For each one, please circle a thought that it was 'very important' that non-indicate how important a reason carriers could be reassured (73% v 56%).

t is, from 0 if you don't think that it Women also saw more of a problem with theportant, to 3 if you think that it is possibility that carriers might not understandtant. Circle '?' if you don't know. that their own health was not affected.

The next two questions were designed toNot Very investigate beliefs about what carriers should

impor- impor- Don't do with that information. Two diseases ('A'tant tant know and 'B') were postulated. For each it was stated0 1 2 3 ? that carrier prevalence is approximately 1 in

20; there is only a problem when both parentsorry people are carriers; if both parents are carriers then,No 48 69 40 11 7 on average, one out of four of their children% 27 39 23 6 4 will be affected and approximately half will be

ldn't interfere carriers; prenatal diagnosis would be availableire and termination would be offered if a preg-No 89 58 11 8 9 nancy were found to be affected. The only% 51 33 6 5 5 differences specified between the two diseasesare told that were the nature and severity of the handicap.

carriers might For disease A it was stated that an affectedrstand that child would be severely handicapped, bothhealth was not physically and mentally, and would die before

the age of 5. Children affected by disease BNo 32 75 43 17 8 would be of normal intelligence, but would% 18 43 25 10 5 have physical problems which could need

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physiotherapy two or three tcontinuous drug treatment. 1some periods when they counormal life and they might liveyears. Question 4 described i

Once that had been answerintroduced disease B. We winterested to discover whetherminated between these two sit

Questions 4 + 5. If a person icarrier which of the followingRemember, both parents haveotherwise there is not a probleage three out of four of their (

healthy. Tick all of the stateagree with.

If they are single they should:

Make sure that thepartner they chooseisn t a carrier

Discuss carrier testingwith any potentialpartner

Not worry about it

Decide not to havechildren

Other

imes a day and It will be seen that little distinction is beingrhere would be made between the two diseases except that,ild lead a fairly where both parents are carriers, childlessnessfor as long as 30 or abortion are more likely to be recommendedonly disease A. for disease A than for disease B. There were-ed, question 5 few differences between men and women, al-ere particularly though men were somewhat more inclined tor parents discri- recommend that carriers should remain child-:uations. less. The greatest difference is seen in the

belief that an affected pregnancy should beis found to be a terminated. While both men and women wereshould they do? more likely to advocate termination for diseaseto be carriers, A than for disease B, the size of the difference

m, and on aver- is much greater for women (44% v 25%) thanchildren will be for men (31% v 27%).ments that you It was then explained that 'Disease B' is

cystic fibrosis, that this is the most commonNo %

serious genetic disease in this country, and thatNo /o a test for carriers may soon become available.

It was also explained that the test would fail toidentify 15 carriers out of every 100 tested and

A 18 10 what the implications would be of each of theB 19 11 combinations of test results that a couple

might get. The explanation concluded as fol-A I A-n on lows.In 1iU OsUB 150 86

A 24 14B 20 11

A 9 5B 9 5

A 2 1B 2 1

If they have a partner they should:

Insist that their pargets tested

Encourage their parto be tested

Not worry about it

Decide not to havechildren

Other

If both members of acarriers, they should:

Not have children

Find other partners

Have tests duringpregnancy to findif the baby is affe(

Have an abortion ifbaby is affected

Not worry about it

Other

A 44 25B 41 23

A 126 72B 132 75

A 15 9B 12 7

A 9 5B 7 4

A 4 2B 4 2

couple are found to be

A 24 14B 16 9

A 3 2'1 -) 1

(Percentages add to more than

people gave more than one re

situation.)

Question 6. The question is: Is it worth peoplehaving such a test under these circumstances?What do YOU think?

No %

Definitely yesPossiblyOnly if there is cystic fibrosis

in the familyDefinitely notDon't know enough to decide

105 6041 23

25 14

4 2

Two thirds of men and just over half of thewomen thought that the test was definitelyworth having. Nobody felt that the test wasdefinitely not worth having, and only fourpeople felt that they did not know enough to beable to decide.Respondents were then asked the following

question.

Question 7. If you have answered 'definitelyyes' or 'possibly', please tick one box to sayhow you think it should be available:

No %

Everyone should have to haveit 8 5

D z I Everyone should be given itA 143 82 unless they object 59 34B 149 85 Everyone should be told about

it and left to decide forA 68 39 themselves whether or not toB 45 26 have it 81 46

Don't know - -A 4 2 Not applicable 27* 15B 7 4 *Should be 29, but two answered the questionA 14 8 anyway.B 12 7 This question is essentially the same as the100 since some first question. There we were asking for basicsponse for each attitudes uncluttered by practical considera-

tions. Here we are asking about a particular

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disease and a particular, imperfect, test andour interest was in discovering whether re-sponses would be modified. Comparison of theanswers to the two questions shows that 68%of the total sample gave the same response inboth cases; 9% advocated wider application ofscreening and 25% more limited availability.Although the numbers are small, it is perhapsof interest to note that women were consist-ently less in favour of compulsion than men.Of the eight people advocating compulsory CFcarrier testing, seven were men.

It was explained that there was some debateas to the best time to offer screening, and thepros and cons of the main options were brieflysummarised. Respondents were then askedwhich they favoured.

Question 8. If cystic fibrosis carrier screeningwere introduced which idea do YOU thinkwould be best?

No %

Test all school leavers 60 34Test all newly pregnantwomen and only test theirpartners if the woman isfound to be a carrier 50 29

Test all newly pregnantwomen and their partners atthe same time 33 19

Test anyone who is notcurrently pregnant but whomight have a child in thefuture 22 13

Wouldn't want it at all 1 1Don't know 2 1Other (please specify) 7 4

The single most popular option, chosen byone third of the sample, was testing all schoolleavers. However, adding together responsesto the second and third options, we see thatnearly half the sample opted for testing at thestart of pregnancy. This seems surprisinglyhigh in a sample who have recently been preg-nant and who might, therefore, be expected toappreciate the drawbacks of such timing.However, it may be precisely because of theirrecent pregnancies that this seemed an obviouschoice. Within those favouring testing at thestart of pregnancy, two thirds of womenthought that men need only be tested if thewoman was found to be positive, while menwere evenly split between the two options.Testing of non-pregnant prospective parentswas not a popular option at all: only 13% ofwomen and 11% of men chose it.The questionnaire concluded'by asking the

following.

Question 9. Finally, we'd like to know whetheror not you think that YOU would be likely toaccept the cystic fibrosis test if it were tobecome available. Please tick one or more ofthe following boxes.

No %

Would definitely not want it 3 2Would have it if partner found

to be a carrier 52 30Would have it if having other

tests done anyway 104 59Would make a special trip tohave it done 84 48

Would take time off work tohave it done 63 36

Would want it enough to payfor it 32 18

Don't know 5 3

(Percentages add to more than 100 since 46%of respondents gave more than one response.)

Nearly half the sample said that they wouldmake a special trip to have the test done. Thiscannot, of course, be taken to be predictive ofuptake in practice since this is a self selectedsample of people who were interested enoughto complete the questionnaire. We might,however, cautiously infer that the 58% of thetarget group who were not even interestedenough to return the questionnaire would beunlikely to want to make a special trip to havethe test done. Of the 52 people who said thatthey would have the test if their partner werefound to be a carrier, five women and nine mengave it as their only response. In one case thisincluded both members of a couple!There was one final question.

Question 10. Finally, could you please circle anumber to let us know how well you feel youunderstood the issues raised in this question-naire.

Didn't Under-under- stoodstand com-at all pletely0 1 2 3 4 5

No - - 5 23 66 80- - 3 13 38 46

(One woman and oneanswer this question.)

man each failed to

DiscussionDespite the small scale of this survey, anumber of interesting points emerge. Subjectsmade relatively little distinction between dif-ferent diseases, although such distinctions aswere made were in the expected direction. Onecan compare this with findings from a surveyofAmerican students carried out in the 1970s,9where 54% advocated termination of Tay-Sachs pregnancies but only 24% gave thisresponse for haemophilia. In that study, how-ever, the options offered to respondents, forexample sterilisation, artificial insemination,were somewhat different from those of thepresent study. Furthermore, the Americansample was better educated and betterinformed about genetics and genetic diseasethan our sample.

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The majority of respondents in this studywere positive about the basic aims that geneticcarrier screening is intended to achieve, al-though a number clearly did appreciate someof the problems, particularly the possibilitythat information might be misused. Argu-ments in favour of screening were consistentlyrated as important, and arguments against asrelatively unimportant. The striking exceptionto this trend was with respect to economicarguments: both those for and against wererejected by the majority of the sample, eventhough the form of the question gave them thefreedom to rate these alongside other argu-ments. Cost was not seen as important evenwhen it could be rated without downgradingother choices. This is consistent with otherfindings on attitudes to medical care.The sample also showed their general sup-

port for genetic carrier screening in their re-sponses to a hypothetical test that would be"quite straightforward and 100% accurate".Nobody supported the view that such a test"should not be available at all". Once thecomplex realities of CF carrier screening wereintroduced, only 60% were prepared to saythat it was definitely worth offering in itspresent form although another 23% thought"possibly". The contrast between these twosituations probably accounts for the discrep-ancy between the current findings and those ofearlier studies,810 I' all of which predate recog-nition of the practical limitations of CF carrierscreening and none of which suggested thatscreening would be other than "quite straight-forward and 100% accurate". A survey in theNetherlands,'0 for example, found that 80% ofnew mothers thought that CF carrier screen-ing should be offered, and the figure was evenhigher for medical students (96%) and for selfselected readers of a local newspaper (90%). Inthe recently published study of Edinburghschoolchildren," 86% thought that routinecarrier screening should be offered. This mayalso account for the numbers saying that theywould want to be screened. Williamson et al8found that 84% of their sample said that theywould want to know if they were a carrier,while in the Dutch study the percentage sayingthat they themselves would make use ofscreening varied from 54% of medical studentsthrough 63% of new mothers to 77% of news-paper readers. The slightly different emphasisof the phrasing between these two studiesprobably accounts for the differences betweenthem. However, none of these studies is likelyto predict what would happen in practice, asthey neither suggest that taking the test hascosts of any kind, nor do they indicate theuncertainties of the result. In the present studyonly 2% said that they definitely would notwant the test but less than half said that theywould be prepared to make a special trip tohave it.

It is also interesting to compare the presentfindings with those of earlier surveys in termsof where and when screening might be carriedout. In two of the studies cited the participantswere not questioned about this, although theauthors make recommendations in favour of

non-pregnant prospective parents in one case'°and adolescents in another." Williamson et al8did ask the question of those who favouredscreening, giving the options of 'GP surgery','referral to hospital', and 'walk in clinic'. Fiftypercent favoured the GP, 33% the hospital,and 17% the clinic. Testing in pregnancy wasnot raised as an option. In the present studypregnancy was, in fact, the most commonchoice. Screening of non-pregnant prospectiveparents was chosen by only 13% of the sampleand testing of school leavers by 34%. Oneargument against testing during pregnancy is,of course, that it deprives people of someoptions, for example, remaining childless orfinding other partners. However, these optionswere not found to have much support in thissample in the hypothetical cases offered; pre-natal diagnosis was easily the most popularchoice. We need to ask the extent to whichpeople would be likely to choose these otheroptions, and to ensure that if a carrier doeschoose, for example, to remain childless, thatthis choice is not made through ignorance ofother options. If this were to happen (as isrumoured to be the case in some sickle cellscreening programmes) then preconceptualtesting would have limited choices, notexpanded them.

Testing in early pregnancy has the majordrawback of time pressures if fetal testing isindicated and also that it is likely to causeanxiety,'2 particularly to women found to becarriers. The concept of 'couple screening',"where only carrier couples would be identified,might be one way of ameliorating the disad-vantages of testing at this time. Clearly manymore people, at least on the basis of the presentsample, would be prepared to be screened atthis time and, in terms of cost effectiveness,targetting women who are already pregnantand actively involved in health care is moreefficient than expending resources on peoplewho may never reproduce in any case.To what extent can the sample reported here

be considered as representative? Firstly weneed to ask why the response rate was so low.The sample had been chosen with the expecta-tion of a much higher response rate than thatwhich was actually achieved. Postal studies ofpregnant women carried out by our team typ-ically achieve around 70% response initiallyand nearer 90% on follow up. Furthermore,the women targetted had all shown their will-ingness to complete questionnaires during thecourse of their recent pregnancies and onlythose who said that they had enjoyed takingpart were included. The target sample was alsolimited to those who were likely to have furtherchildren, the assumption being that the issueswould have greater relevance to this group. Sowhy did not more respond? It may be that theywere all too busy with their new babies, or thatthey felt that they had already done enough forus. All had recently had a healthy child whichmay have led them to think that they were notthemselves at risk, and that the subject wasnot, therefore, relevant to them. It may also bethat the issues were difficult to understand, thequestionnaire too long, or simply that the topic

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did not engage their attention. These latterexplanations seem very likely, particularlywhen we see that most respondents claim tohave had a reasonable understanding of theissues raised. Presumably those who did notunderstand did not respond. This is a probleminherent in any attempt to offer mass screen-ing: the issues are not simple to understand,neither are conditional probabilities, and thelong term implications may not be apparent atall.The hazards of offering CF carrier screening

at present have been clearly described byWilfond and Fost.14 Nevertheless, it is evidentthat many professionals in the field do notaccept all the arguments, especially those relat-ing to the social implications. If professionalshave not fully grasped the issues, how then canordinary lay people be expected to? The re-sults reported in this paper can only be takenas the responses of a minority group who wereprepared to grapple with the issues, success-fully or otherwise, and not as being representa-tive of all new parents. The problems of ensur-ing that all potential subjects of carrierscreening are making genuinely informed de-cisions should not be underestimated.

The questionnaire used in this study under-went a number of metamorphoses in the at-tempt to convey the issues raised by geneticscreening to a non-specialist audience. This

process was greatly aided by the critical com-ments of Martin Bobrow, Martin Richards,Helen Statham, and Claire Snowdon, to all ofwhom I am most grateful.

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3 Angastiniotis M. Cyprus: thalassaemia programme. Lancet1990;336:1 119-20.

4 Modell B, Petrou M, Ward RH, et al. Effect of fetaldiagnostic testing on birth rate of thalassaemia major inBritain. Lancet 1984;ii:1383-6.

5 Prashar U, Anionhwu E, Brozovic M. Sickle cell anaemia -who cares? London: Runnymede Trust, 1985.

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7 Green JM. 'Is the baby alright?' and other worries. Paperpresented to the 10th Annual Conference of the Societyfor Reproductive and Infant Psychology, Girton College,Cambridge, 11 September 1990.

8 Williamson R, Allison MED, Bentley TJ, et al. Communityattitudes to CF carrier testing in England: a pilot study.Prenat Diagn 1989;9:727-34.

9 Margolin CR. Attitudes towards control and elimination ofgenetic defects. Soc Biol 1978;25:33-7.

10 Ten Kate LP, Tijmstra TJ. Carrier screening for cysticfibrosis. Lancet 1989;ii:973-4.

11 Cobb E, Holloway S, Elton R, Raeburn JA. What do youngpeople think about screening for cystic fibrosis? J MedGenet 1991;28:322-4.

12 Green JM. Calming or harming? A critical review of psycho-logical effects offetal diagnosis on pregnant women. GaltonInstitute Occasional Papers, Second Series, No 2, 1990.

13 Wald N. Parental antenatal screeningfor cysticfibrosis. Paperpresented to a Workshop on Cystic Fibrosis CarrierScreening, Medical Research Council Headquarters,London, 17 December 1990.

14 Wilfond BS, Fost N. The cystic fibrosis gene: medical andsocial implications for heterozygote detection. JAMA1990;263:2777-83.

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Principles practicalities of carrier screening: attitudes