Costs and benefits of cervical screening IV: valuation by women of the cervical screening programme

Costs and bene®ts of cervical screening IV: valuationby women of the cervical screening programme

SARAH WORDSWORTH* MANDY RYAN* AND NORMAN WAUGH***Health Economics Research Unit, University of Aberdeen, UK, **Wessex Institute forHealth Research and Development, University of Southampton, UK

Accepted for publication 6 July 2001

WORDSWORTH S., RYAN M. AND WAUGH N. (2001) Cytopathology 12, 367±376

Costs and bene®ts of cervical screening IV: valuation by women of the cervical screeningprogramme

Objectives: To assess the value of the cervical smear test to women, taking account of thepositive and negative aspects of the cervical screening service.Design: A postal survey.Setting: Tayside Health Board region of Scotland.Participants: A sample of 2000 women aged 20±59.Main outcome measures: Maximum willingness to pay (WTP) for a cervical smear test.Results: Women were prepared to pay £50.20 per smear on a 3-yearly basis. Willingnessto pay was positively related to income, but unrelated to age and whether or not therespondent had previously had a smear.Conclusions: Previous studies have estimated the cost per screen or cost per life year savedby cervical screening. This study used the economic instrument of WTP to take account ofother potential (dis)bene®ts to women. The value women place on having a smear wasmore than the cost to the National Health Service (NHS) of providing the service. Theoutput of a WTP study is potentially useful at the policy level. Future work should exploreboth the value of alternative approaches to cervical screening, and the value of competinghealth care interventions.

Keywords: cervical screening, bene®ts, willingness to pay

INTRODUCTION

Limited resources, coupled with ever increasing demands for health care, mean thatdecisions have to be made regarding the optimal allocation of scarce health care resources.

Correspondence: Sarah Wordsworth, Health Economics Research Unit, University of Aberdeen, Medical School,

Foresterhill, Aberdeen AB25 2ZD, UK. Tel.: 01224 553866; Fax: 01224 662994; E-mail: s.wordsworth@abdn.

ac.uk

Ó 2001 Blackwell Science Ltd

Cytopathology 2001, 12, 367±376

Economic evaluation provides a framework to help inform the decision making process.1

Economic evaluations of cervical screening programmes have attempted to informdecision making concerning the optimal provision of cervical screening programmes. Todate such evaluations have largely adopted a cost-e�ectiveness framework, estimating suchfactors as cost per life saved or cost per life year saved. For example, in a previous series inthis journal looking at the costs and bene®ts of cervical screening, Waugh and Robertsonestimated that the cost per life saved from reducing the screening interval from 5 years to3 years would be around £250 000 pounds at 1995 prices, or around £8000 per life yearsaved.2 A similar approach has been adopted in other studies.3,4

Whilst such an approach provides valuable information, it omits factors beyond thesaving of lives that may be important to women in the provision of cervical screeningprogrammes. Waugh and Robertson note that there would be human costs for the womenscreened. These human costs can be more accurately de®ned as disbene®ts of the service.*

Austoker (1999) noted that the detrimental e�ects of screening include anxiety, falsealarms, false reassurance, unnecessary biopsies, overdiagnosis and overtreatment5. Thesefactors have been highlighted in other studies, alongside such factors as the discomfort andindignity of the test.6±8 There are also potential bene®ts, beyond a reduction in the chanceof dying, from a cervical screening programme. These include information andreassurance provided by screening.Given the possible bene®ts and disbene®ts derived from cervical cancer screening

programmes, an evaluation technique is needed that can take account of these factors.Developments in the methods of bene®t assessment have produced techniques to achievethis.9 One example is the economic instrument of willingness to pay (WTP).10 Thistechnique is based on the principle that the maximum amount of money an individual iswilling to pay for a commodity is an indication of how much they value that commodity.It is also argued that when stating their maximum WTP, individuals will take account ofall factors that are important to them. For instance, in considering maximum WTP for ahouse, individuals consider all the relevant characteristics such as location, number ofbedrooms and whether the house has central heating and double-glazing. Based on thesecharacteristics they derive a maximum WTP. When applied to cervical screeningprogrammes, individuals should consider all positive and negative factors that areimportant to them in the delivery of the service.Grimes applied such an approach to establish the value of a negative cervical smear

result.11 He asked 100 women who had recently had a normal smear whether they felt thenegative smear was of value to them and, if so, what was the monetary value of theinformation. Sixty-nine women completed the questionnaire, and were prepared to pay amean of £8.25 for the negative cervical smear. The study presented here takes the Grimesstudy forward by posing the WTP question to women before their next screen. Our WTPstudy was carried out in 3 groups of women who di�ered according to smear status: thosewho had never had a smear, those who attended and had always had normal smears, andthose who had had an abnormal (non-cancerous) result.

*It should be noted that items to be included on the cost side of an economic evaluation are any `resources' which

have an alternative use. Often, costs (and bene®ts) are mis-classi®ed within economic evaluations. For example,

anxiety has often been counted as a `cost' and cost savings as `bene®ts'. However, anxiety per se does not have an

`opportunity cost' ± it is not a resource which could be used in some other activity. Anxiety is a negative e�ect on

health or wellbeing and should be accounted for on the bene®t side of an evaluation. Likewise, `cost savings' are

negative costs and should be accounted for on the cost side.

368 S. Wordsworth et al.

Ó 2001 Blackwell Science Ltd, Cytopathology, 12: 367±376

METHODS

Population

The study population was a sample of women aged 20±59 in the Tayside Health Boardregion of Scotland. A strati®ed sample of 2240 women in this age group was identi®edfrom the Online Cervical Cancer Update Recall System (OCCURS), a computer-basedsystem giving the names and addresses of all women aged 20±59 eligible for screening forcervical cancer in the Tayside area.12 The strati®cation was undertaken to providesu�cient numbers for statistical analysis according to age and smear status. It washypothesised that these di�erent groups would value the screening programme di�erently.A pilot questionnaire was mailed to 240 of this sample. The main study was mailed to theremaining 2000, with a prepaid return envelope included. If individuals did not wish totake part in the study they were encouraged to return a slip stating this. Two reminderswere sent. The ®rst reminder included a letter, the second a letter and an additional copy ofthe questionnaire.

The `Willingness to pay' (WTP) questionnaire

The WTP questionnaire was included as part of a larger questionnaire examining women'spreferences for cervical screening. An attempt was made to inform women about theprocedures involved when having a cervical smear (since some had never attended).Women were told that the current method of carrying out screening to detect cervicalcancer was the conventional `smear' test and a description of the test was provided.Information was provided on the cervical screening programme in Tayside at the time ofthe study. Respondents were informed that the time between smears was 3 years and thatif they underwent screening; the time for results was 10 days; their chance of being recalledwas 15%; their chance of having an abnormality was 8% and their chance of dying from acervical cancer if they undertake screening was 0.8%. They were informed that the vastmajority of recalls are for technical reasons or non-cancerous abnormalities, and not forcancerous abnormalities. They were also told that whilst only a small percentage ofabnormalities will be cancerous, having an abnormality will result in a need for furthersmears. A copy of the questionnaire is available from the authors on request.The women were advised that the questionnaire was concerned with the value they place

on screening for cervical cancer, and that one way to establish this is to ®nd out themaximum amount of money that they would be willing to pay for each smear. Assurancewas given that they would not have to pay the amount that they stated and that the WTPquestion was just a way of ®nding out how much they valued having a smear. To increaserealism, the women were reminded that any money they spent on a smear test would notbe available to spend on other things, such as food or holidays.Maximum WTP was then elicited. There are four main ways to collect WTP data from

responses to hypothetical questions: open-ended, closed-ended, bidding or payment cardmethod.13 An open-ended questionnaire asks the respondent directly for their maximumWTP. A bidding questionnaire presents respondents with an initial amount, which theyeither accept or reject and they bid up, or down, in increments until their maximum WTPare reached. Closed-ended questionnaires, also known as discrete-choice, referendum,dichotomous-choice or binary questionnaires, present respondents with a single WTP

Costs and bene®ts of cervical screening 369


value, or bid, which they either accept or reject.14 This study used the payment cardtechnique, or categorical scale, which has been widely used in health economics. Hererespondents are presented with a range of bids and asked to circle the amount thatrepresents the most they would be willing to pay. Given that the latter technique is arguedto be close to the `shopping around' behaviour that individuals adopt in the market place,it was used in this study.15

Individuals were presented with a payment card with the following ranges: £0, £5, £10,£15, £20, £25, £30, £35, £40, £50, £60, £70, £80, £90, and £100. The women were asked totick `Yes' if they would de®nitely be willing to pay that amount per smear, tick `No' if theywould de®nitely not be willing to pay that amount per smear and to circle the maximumamount they would be willing to pay per smear. Respondents who stated they were willingto pay more than £100 were asked their maximum WTP. This payment card was reviewedafter the pilot study to ensure that a su�cient range of values was being covered. This wasexamined by assessing the spread of WTP values, with particular attention given towhether respondents were stating a value higher than £100.Information was also collected on how long the WTP question took to complete and

ease of completion. To assess the latter, respondents were asked how di�cult they foundthe WTP question using a 1±5 scale, where 1 was `very easy' and 5 was `very di�cult'.Further information was collected on respondent's age, gross household income andsmear status (whether they had ever had a smear, and if yes, had they ever had anabnormal result). The Kruskal±Wallis test was used to examine whether there was arelationship between WTP and both age and smear status. Regarding the latter, thehypothesis was that women who had received an abnormal result would have a higherWTP. No hypothesis was made with respect to age. The Spearman's Rho test was used totest for a relationship between income and WTP, where a positive relationship wasexpected, that is, the higher the income level the more the women would be willing to pay.Testing for a relationship between income and WTP variables is an indirect way of testingfor the methodological rigour of the WTP technique. A priori we would expect those onhigher incomes to be willing to pay more. This does, however, raise questions concerninghow to use such results at a policy level. This is discussed below.

RESULTS

Of the 2000 questionnaires mailed, 595 were returned completed (30%), 250 had moved(13%), 500 did not wish to participate (25%), 20 (1%) felt it was not relevant and 636(32%) were not returned. The average age of respondents was 38, and most fell into theincome range of £10 000 ± £25 000. The majority of respondents had had a smear, with266 reporting a `normal' result, and 222 an àbnormal' result. Forty respondents had neverhad a smear.The mean completion time for the WTP question was 3.6 min and most women found

the questionnaire either `very easy' or èasy' to complete. Thirteen respondents (2%) didnot answer the WTP question itself, so were excluded from further analysis. Elevenpercent (62/582) of respondents placed a zero value on the cervical screening test. Thereasons for such responses were òbject to paying' 30 (48.4%); `do not value' 5 (8.1%);`cannot a�ord' 11 (17.7%); `no reason' 3 (4.8%) and òther' 13 (21%). For the latter, `theNHS should be free to all' was the most common response.



For those women who did provide a WTP value (including the usable zero values), themean WTP for the current cervical screening service in Tayside was £50.20 (Table 1). Therelationship between WTP and income, age and smear status is shown in Table 2. Incomewas signi®cantly related to WTP with the women in the lowest income group (£6000 and

Table 1. WTP for a cervical screening test in Tayside

Rate of completion 30.8% (595/2000)

WTP � £0 10.7% (62/595)Mean WTP (£) 50.20Median (£) 45.00

Standard deviation (£) 32.00Maximum (£) 150.00

Table 2. WTP by income, age and smear status

Income N � 508 Mean WTP (£) Median (£)

Standard

deviation (£)

Less than £6000 84 37 33 32

£6000 to £10 000 59 42 32 31£10 000 to £15 000 77 48 38 27£15 001 to £20 000 69 50 55 30

£20 001 to £25 000 78 47 45 28£25 001 to £30 000 41 56 55 32£30 001 to £35 000 34 63 55 33£35 001 and greater 66 70 65 35

(Spearmans rho � 0.301P � 0.000)

Age group n � 532

18±29 135 47 45 29

30±40 160 53 55 3441±50 170 51 45 3151 + 67 47 32 34

(Kruskal±Wallis test,Chi square � 3.173P � 0.366)

Smear status n � 528

Previous had smear,

result normal

266 50 45 32

Previous had screening,result abnormal smear

222 50 45 32

Never had a smear 40 48 55 32(Kruskal±Wallis test,Chi square � 0.19

P � 0.990)



less) being prepared to pay a mean of £37.00 compared to those in the highest incomegroup (£35 001 +) who were prepared to pay £66.00 (rho � 0.301, p � 0.000). Those whohad never had a smear were willing to pay slightly less than those who had undergonescreening (£48.75 compared to £50.20), but this was not statistically signi®cant (v2 � 0.19,p � 0.990). Further, age was not related to WTP (v2 � 3.173, p � 0.366).

DISCUSSION

The ®ndings in this study suggest that despite recent criticism of the quality of cervicalscreening programmes in the UK, and the potential disbene®ts associated with the test,women still value cervical screening programmes. Mean WTP for a cervical smear test wasestimated to be £50.20. This value takes account of consumer/patient views, and considersall the bene®ts and dis-bene®ts of the cervical screening programme. A criticism of manysurvey methods for eliciting patient views is that they are often not useful at a policy level.However, willingness to pay information can prove useful to policy makers. Suchinformation allows costs to be directly compared with bene®ts. Waugh et al. estimated asmear test, including follow-up of smears where abnormalities were found, to cost£22.70.12 Adjusting this to 1998 prices gives a cost per screen of £26.32. Comparing thiscost with (dis)bene®ts indicates that the overall gains to women of being screened everythree years would outweigh the costs of this procedure.WTP data will also prove useful in comparing the bene®ts of cervical screening

programmes with those of close substitutes (i.e. alternative ways of providing cervicalscreening programmes) or disparate health care interventions (i.e. cervical screeningprogrammes vs. prenatal screening programmes vs. heart interventions vs. infertilitytreatment) within the framework of a cost bene®t analysis (CBA). Here costs and bene®tsare measured in the same unit (usually money) and directly compared. The provision ofthe service may be encouraged if bene®ts outweigh costs. However, such a decision rule isnot su�cient when deciding on the provision of a publicly provided commodity within a®xed budget context (such as health care). This is because too many interventions maypass these criteria and therefore choices have to be made. This is where the economicsnotion of opportunity cost arises. Using resources in any particular way implies that theyare not available for any alternative use. The opportunity cost of the resources is the valueof the bene®ts that would arise from their best alternative use. This implies that a singleWTP study is of little use for the setting of priorities within a given budget. Comparisonsshould be made with other interventions, which may be close substitutes, or disparatehealth care interventions. This raises the question of how the results from this study can beused. One possibility would be for the results to be compared to other WTP studieslooking at alternative health care interventions. For example, within the context ofscreening for cystic ®brosis, Donaldson et al. estimated WTP to be £18.00 for stepwisetesting and £22.00 for couple testing.18 Comparing the data in this study with that ofDonaldson et al. suggests that cervical screening is valued more highly than carrierscreening for cystic ®brosis, implying that the former should have a higher priority forimplementation (assuming a similar level of resource use). However, such a comparisonrequires WTP values to be insensitive to such factors as the framing of the question (seebelow). If this is not the case, a better way to proceed would be to ask respondents theirWTP for competing health care interventions within the same questionnaire. Such anapproach has been adopted by Donaldson et al. in a recent study looking at the value of



introducing three disparate competing health care interventions: a helicopter ambulanceservice; additional hip replacements and additional heart transplants.19

Whilst WTP studies o�er useful information at the policy level, a number of concernsare often raised when using the technique. These relate to such factors as response rates,the level of information of respondents, potential strategic biases, the sensitivity of theresults to the framing of the question, the potential for `cost-based' responses and therelationship between income and willingness to pay.The response rate for those who had never had a smear was 7%. This indicates that this

group were underrepresented in the returned questionnaires. Future studies shouldattempt to elicit the values of this group. Further, the majority of women who felt that thequestionnaire was irrelevant to them had had a hysterectomy. These women should nothave been sent the questionnaire (the computer programme had failed to update theirrecords). Attempts should be made to ensure that cervical, as well as other health relateddatabases, are up to date. Failure to do this may lead to unnecessary upset. For example,out of date databases may result in reminders being sent to women who have died fromcervical cancer.This study did not collect data on women's perceived risk of dying from cervical cancer

and hence no data was available on how respondents perceived their risk of dying wouldchange if they underwent screening. It is possible that respondents were not fully aware oftheir own risk of cervical cancer, and therefore they may have either underestimated oroverestimated the bene®t to themselves. It is worth noting here that the underlying risk ofcervical cancer has changed for di�erent birth cohorts in Scotland with women born since1960 being several times more likely to die from cervical cancer (in the absence ofscreening) than those born in the 1930s. The fact that no evidence was found in this studyof a relationship between WTP and age suggests that women may not be aware of thisrelationship. Future work should explore women's knowledge concerning their risks ofdying from cervical cancer.Concerning strategic biases, a statement was included in our questionnaire emphasizing

that there is no way subjects would have to pay the amount speci®ed, and that the aim wasto establish the value of the health care intervention being examined. This statement wasincluded because using WTP in the area of health care in the UK National Health Service(NHS) is politically sensitive. Health care providers are often concerned that includingsuch questions will lead to suggestions that they are attempting to privatize the health caresystem. They have therefore insisted on such a statement being included. However, such astatement may invite respondents to overstate their WTP. Two studies have directly testedthe overbidding hypothesis in the WTP literature, i.e. that respondents overstate their truevalue when they are told they will not have to pay for the proposed change (though noneof these are applied to health care). Bohm found no evidence of such strategic behaviourwhen looking at the value of TV programmes,20 whilst Posavac found the opposite resultwhen looking at the value of student accommodation.21 Future work within health careshould address the sensitivity of WTP estimates to such statements. Consideration mayalso be given to alternative ways of wording the WTP question. One possibility would beto ask respondents how much they think the Health Board or Health Authority shouldspend on cervical screening. However, there is evidence that when phrasing the WTPquestion in this way respondents do not consider the opportunity cost and they say `yes' toall amounts presented to them.22 An alternative approach would be to use a `willingness toaccept' type approach. Here respondents would be asked if the Health Board o�ered them



the option of cash instead of a smear test, how much would they be willing to accept toforgo the smear test. There is however, evidence that willingness to accept values aresystematically higher than WTP values.23 Another approach would be to ask the questionin terms of current taxation.19

Regarding the framing of questions, concerns may be expressed that values elicited inWTP surveys may be sensitive to the levels presented in the survey. Within the contextof this study this raises the question of whether the values elicited would have beendi�erent if a di�erent payment card had been presented. To date there is no evidenceon the sensitivity of WTP estimates to the bid vector and future work should explorethis.Concern has been expressed in the WTP literature concerning the presence of `cost-

based responses'. When eliciting values in a WTP survey the researcher is not interestedin what the respondent perceives to be the cost of the care, but rather the value of thatcare. However, previous research has shown that cost-based responses do occur, with therespondents taking into account the ®nancial cost of providing the service being valuedwhen giving a WTP value. Ryan et al. conducted a WTP study examining twoalternative treatments for menorrhagia (conservative treatment compared to hysterec-tomy).24 The results showed that while women preferred the conservative option, theywere willing to pay more for hysterectomy. One explanation for this was that theyperceived hysterectomy to be more expensive. Evidence of cost-based responses was alsofound in the cystic ®brosis study by Donaldson et al.15 Within the context of this study,there is a private market for cervical screening tests. If women knew how much it coststo be screened in the private sector this may have in¯uenced their WTP response. Futureresearch should investigate possible ways of overcoming cost-based responses in WTPstudies.24

A common criticism of the WTP instrument is that WTP is related to ability to pay.Such a relationship was found in this study. From a theoretical perspective this would beexpected, i.e. we would expect those on a high income to be willing to pay more. Theextent of this problem from a policy perspective depends on the nature of the questionbeing asked. If respondents are being asked their WTP for a single health careintervention (as in this study where values for a given cervical screening programme wereelicited) then it may be argued that given the current distribution of income, WTPrepresents in some way the value the community places on that screening programme(assuming a representative sample). There are of course issues raised about the fairnessof this distribution. Potential problems do, however, arise with the relationship betweenWTP and ability to pay when (i) values are being elicited for close substitutes and/ordisparate health care interventions and (ii) di�erent income groups have di�erentpreference structures for these close substitutes/disparate health care programmes (i.e.low income groups prefer cervical screening programmes and high income groups heartinterventions). For example, if low income groups prefer cervical screening programmesand high income groups heart programmes, and resources are allocated between thesetwo interventions on the basis of WTP, the relationship between WTP and income willmean that the value for hearts has been `contaminated' by the greater purchasing powerof those preferring that programme. Donaldson25 notes that when income groups havedi�erent preference structures, and preferences are being elicited for close substitutesand/or disparate health care interventions, distributional weights could be applied to theWTP estimates `to highlight the e�ects of such weights on WTP values and to establish



the critical values of such weights at which options would be equally valued'. Thissuggests that WTP studies that are eliciting preferences for close substitutes and/ordisparate interventions should also collect information on preference structures. If thesestructures di�er across income groups consideration should be given to the use ofdistributional weights.

CONCLUSION

In conclusion, this paper has demonstrated the use of WTP and has assessed the valueof the cervical screening smear test to women. In contrast to cost-e�ectiveness studies,this project took account of all the positive and negative aspects of the cervicalscreening service. The WTP technique was shown to be a useful instrument for thevaluation of bene®ts in health care. WTP was found to be £50.20, positively related toincome, but unrelated to age and smear status. Future research must address issuesrelated to response rates, respondent's knowledge, strategic biases, the framing of theWTP question, cost based responses and the relationship of WTP values to income. Itshould also be noted that this study elicited values for a given cervical screeningprogramme where the screening interval was every 3 years. Future studies could applyWTP to assess the value of cervical screening programmes, which vary with respect tosuch factors as cancer incidence, speci®city of test, and frequency of screening. Indeed,one advantage of the WTP approach is that it allows valuation of health careinterventions, which have not yet been introduced. When using WTP numerousquestions could be presented to individuals. An alternative approach would be to useconjoint analysis (also known as discrete choice experiments) to estimate WTPindirectly. When using this approach, individuals are presented with choices betweenservices described in terms of levels of prede®ned attributes and asked, for each choice,to choose their preferred one. In the case of cervical screening policy questions, possibleattributes could be accuracy of the test, waiting time for results, and frequency ofscreening. From a conjoint analysis exercise it is possible to estimate the relativeimportance of di�erent attributes in the provision of that service, the rate at whichindividuals trade between these attributes, and the monetary value of marginal shifts inthe attributes of interest (i.e. willingness to pay for screening to be every 2 years ratherthan every three years, or willingness to pay for a 1-day reduction in waiting time forresults).26,27 Future research should explore economic approaches to valuing alternativecervical screening programmes.

ACKNOWLEDGEMENTS

The authors would like to thank Alisdair Robertson for help in setting up this project,sta� at the East of Scotland NHS Computer Consortium, and sta� at Grampian HealthBoard for assisting with a prepilot of the questionnaire, Angela Bate for comments onthe paper and the women who responded to the questionnaire. Financial support isacknowledged from the Medical Research Council (MRC) and the Chief Scientist O�ceof the Scottish Executive Health Department. The views expressed in the paper are thoseof the authors.



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Costs and benefits of cervical screening IV: valuation by women of the cervical screening programme

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