a cost–utility analysis of tension-free vaginal tape versus colposuspension for primary urodynamic...

A cost–utility analysis of tension-free vaginal tape versuscolposuspension for primary urodynamic stress incontinence

Andrea Mancaa,*, Mark J. Sculphera, Karen Wardb,c, Paul Hiltonb,c

Objective To assess the cost effectiveness of tension-free vaginal tape compared with open Burchcolposuspension as a primary treatment for urodynamic stress incontinence.

Design Cost–utility analysis alongside a multicentre randomised comparative trial.

Setting Gynaecology or Urology departments in 14 centres in the UK and Ireland, including University-associated teaching hospitals and district general hospitals.

Population Women with urodynamic stress incontinence. Exclusion criteria were: (1) detrusor overactivity;(2) major voiding problems; (3) prolapse; (4) previous surgery for incontinence or prolapse.

Methods Resource use data were collected on all 344 patients in the trial, including length of hospital stay,time in theatre and management of complications; resource use was costed using UK unit costs at 1999–2000 prices.

Main outcome measures Health outcomes were expressed in terms of quality-adjusted life years (QALYs)between baseline and six months follow up, based on women’s responses to the EQ-5D health questionnaire.

Results Tension-free vaginal tape resulted in a mean cost saving of £243 (95% CI £341 to £201) comparedwith colposuspension. Differential mean QALYs per patient (tension-free vaginal tape � colposuspension)was 0.01 (95% CI �0.01 to 0.03). The probability of tension-free vaginal tape being, on average, less costlythan colposuspension, was 100%, and the probability of tension-free vaginal tape being more cost effectivethan colposuspension was 94.6% if the decision-maker was willing to pay £30,000 per additional QALY.

Conclusion The results from this trial suggest that, over a post-operative period of six months, tension-freevaginal tape is a cost effective alternative to colposuspension. The results will need to be reassessed on thebasis of longer follow up.

INTRODUCTION

Urinary incontinence is a significant health problem,

with 14% of women reporting the symptoms1. Urodynamic

stress incontinence accounts for approximately 50% of

urinary incontinence in women presenting to hospital2.

Physiotherapy has a cure rate of about 50%3 – 5, and surgery

is recommended for those women who fail to respond.

Colposuspension is the most frequently used form of

primary therapy for urodynamic stress incontinence, but

the morbidity and resource use associated with the proce-

dure are considerable.

A recent development in the treatment of urodynamic

stress incontinence is the use of a prolene tape (tension-free

vaginal tape) inserted using a tunnelling approach rather

than open dissection of the retropubic space. This can be

done under local anaesthesia and can be undertaken using

day-case admission6, allowing more rapid return to normal

activity. Given that the use of tension-free vaginal tape

results in changes in a range of health care resources as

well as health outcomes, it is important to assess its cost

effectiveness relative to standard surgical management with

colposuspension.

A multicentre prospective randomised controlled trial

comparing tension-free vaginal tape and Burch colposus-

pension for ‘primary’ urodynamic stress incontinence has

been undertaken in the UK7. As part of the study, patient-

specific resource use and health-related benefits were

prospectively collected during hospitalisation and for a

period of six months after discharge from hospital. This

paper reports the results of a cost–utility analysis under-

taken using these data, adopting a UK National Health

Service perspective.

METHODS

Full details of the design of the trial have been published

elsewhere7. Briefly, the clinical study was a prospective

multicentre randomised controlled trial enrolling 344

BJOG: an International Journal of Obstetrics and GynaecologyMarch 2003, Vol. 110, pp. 255–262

D RCOG 2003 BJOG: an International Journal of Obstetrics and Gynaecology

doi:10.1016/S1470-0328(03)02915-X www.bjog-elsevier.com

aCentre for Health Economics, University of York, UKbDirectorate of Women’s Services, Royal Victoria

Infirmary, Newcastle upon Tyne, UKcDepartment of Obstetrics and Gynaecology, University of

Newcastle upon Tyne, UK

* Correspondence: Dr A. Manca, Centre for Health Economics,

University of York, Heslington, York, YO 10 5DD, UK.

women diagnosed with ‘primary’ urodynamic stress incon-

tinence. Patients were recruited to the trial from urogynae-

cology, general gynaecology and urology outpatient clinics

between May 1998 and August 1999, and were randomised

to either colposuspension (n ¼ 169) or tension-free vaginal

tape (n ¼ 175). A total of 34 women dropped out from the

study, 28 before surgery (23 colposuspension, 5 tension-

free vaginal tape) and 6 afterwards (4 tension-free vaginal

tape, 2 colposuspension). Of the 23 women who did not

undergo surgery in the colposuspension group, 20 withdrew

their consent, 2 discontinued the study due to protocol

violation and 1 patient withdrew for other reasons. Of the

five women who did not have surgery in the tension-free

vaginal tape arm, two withdrew their consent, two violated

the protocol and one withdrew for other reasons. Of the four

women who dropped out from the tension-free vaginal tape

group after surgery, two had a treatment failure, one did not

return for the follow up visit and one withdrew for other

reasons. Finally, one of the two women who decided not to

continue the study after colposuspension withdrew her

consent, while the other did not return for the follow up visit.

Baseline characteristics and clinical results of the ran-

domised trial are detailed elsewhere7. Women who pre-

sented with urodynamically proven stress incontinence

were invited to participate in the trial. Exclusion criteria

were detrusor overactivity, vaginal prolapse requiring treat-

ment, previous surgery for prolapse or incontinence, a

major degree of voiding dysfunction, neurological disease

and allergy to local anaesthetic. In terms of clinical results,

there was no statistically significant difference between the

cure rate in the two groups: 115 (66%) women in the tension-

free vaginal tape group and 97 (57%) in the colposuspension

group were objectively cured. Subjective cure of stress

incontinence was reported by 103 (59%) and 90 (53%) of

women in the tension-free vaginal tape and colposuspension

arm, respectively. This economic evaluation is conducted on

an intention-to-treat basis and includes only the 316 women

who underwent surgery.

Using case report forms completed by clinical staff,

patient-specific data on resource use were prospectively

recorded from hospitalisation to six months from discharge.

Where resource use was not expected to vary between

patients, estimates based on clinical expert advice were

used. Data were collected on resource use during two study

periods: main hospitalisation and follow up at six months.

The former comprised resource use in theatre, inpatient stay

and post-operative complications. Theatre resource use

included staff present (in holding bay, anaesthetic room, op-

eration theatre and recovery area) based on clinical advice;

consumables (in theatre and anaesthetic room); and drug use

(i.e. thromboprophylactics, anaesthetics and antibiotics).

Theatre resource use included any extra tension-free vaginal

tapes. Drugs used for anaesthesia, thromboprophylaxis, se-

dation and the prophylactic antibiotic regimen were set by

the protocol. Other patient-specific theatre resources com-

prised those associated with intra-operative complications.

Inpatient stay was the number of nights spent in the general

ward by each woman. Post-operative resource use included

that related to management of complications (e.g. fever,

wound infection, urinary tract infection), additional consum-

ables (e.g. drains, catheters), post-operative analgesia and

any return to theatre during main hospitalisation. Finally, the

six-month post-operative visit to clinic facilitated the col-

lection of data on additional surgical procedures, use of

concomitant medications, re-hospitalisations, number of

outpatient and day-case visits and general practitioner con-

tacts since hospital discharge.

The differential cost of treating patients in the two arms

of the trial was estimated by valuing the resource use

measured in the study using UK unit costs estimated at

1999–2000 prices, including value-added tax where appro-

priate. Staff time was costed using mid-range salaries

uprated for employers’ costs8 – 10. Consumables were costed

using manufacturers’ list prices, and drug costs were based

on those reported in the British National Formulary11.

Inpatient stay was costed using an estimated average hotel

cost per day in a gynaecological ward obtained from a

survey of three UK hospitals undertaken in 1995 and

uprated for health service inflation12. We assumed the hotel

cost of a day-case visit to be equal to the cost of an

outpatient visit13. Finally, the cost of a general practitioner

consultation was obtained from published estimates8. The

main unit costs used in the analysis are reported in Table 1.

The health outcomes of treatment, over six months follow

up, were expressed in terms of quality-adjusted life years

(QALYs). In order to measure women’s health status at

various points in time, women were asked to complete the

EQ-5D health questionnaire14 at baseline, at six weeks and

six months after hospital discharge. This is a standardised

non-disease specific instrument designed to describe and to

Table 1. Key unit costs used in the analysis.

Item of resource Unit Unit cost (£) Source

Ward ‘hotel’ cost Day 103.00 Ref. 12

Theatre

Staff (tension-free vaginal tape) Minute 2.24 Refs 8– 10

Staff (colposuspension) Minute 2.87 Refs 8– 10

Anaesthetic room

Staff Minute 0.85 Ref. 9

Recovery area

Staff Minute 0.20 Ref. 9

Overheads Minute 2.33 Ref. 12

Key consumables

Tension-free vaginal tape Item 359.45 Ethicon

Staple gun Item 113.42 Ethicon

Outpatient and day-case visits Visit 62.00 Ref. 13

General practitioner visit Visit 15.75 Ref. 8

256 A. MANCA ET AL.

D RCOG 2003 Br J Obstet Gynaecol 110, pp. 255–262

value health status. Health status is defined in terms of five

dimensions: mobility, self-care, usual activities, pain or

discomfort and anxiety or depression. Each of these dimen-

sions has three levels of severity: no problems, moderate

problems or extreme problems. In completing the EQ-5D, a

patient defines their health state in terms of the five dimen-

sions, which is transformed into a weighted health state

index score or ‘utility’. Using values elicited from the UK

population15, the index typically ranges between 0 (equiva-

lent to death) and 1 (equivalent to good health), although a

small number of health states are valued as worse than death.

EQ-5D scores at baseline, six weeks and six months were

used to calculate patient-specific QALYs, which were esti-

mated using the area under the curve method16,17. This is

achieved, for each patient, by weighting the time between

the three EQ-5D responses using the health state index score.

Therefore, the QALY seeks to capture the impact of the

alternative treatments in terms of both morbidity and mor-

tality on a single dimension.

Statistical analysis was undertaken using STATA 6.018.

Estimates of mean costs and QALYs for the two treatment

arms were calculated over six months follow up. Costs have

been grouped under four headings: theatre cost, hospital

‘hotel’ (i.e. ward) cost, other post-operative complications

and follow up cost at six months. To indicate the pattern of

the health outcomes over the study period, EQ-5D scores at

baseline, six weeks and six months have been reported.

Given that the time horizon of the analysis was less than a

year, total costs and QALYs remain undiscounted.

To account for the skewed nature of the resource use

data, 95% confidence intervals for the differential costs and

QALYs have been calculated using non-parametric boot-

strap (based on the 2.5th and 97.5th centiles)19,20. In some

patients, resource use data and EQ-5D responses were

wholly or partially missing. Under the assumption that data

were missing completely at random21,22, those observations

where either length of stay in theatre or one of the EQ-5D

assessments was missing were excluded from the base case

analysis. As a result, 53 observations in the tension-free

vaginal tape group and 49 in the colposuspension group

were excluded from the initial analysis, and the base-case

analysis was conducted on a complete case data set of 214

Table 2. Main resource use measured during the trial based on the complete case analysis. Values are expressed as n (%), mean [SD] or median

{interquartile range}.

Item of resource Tension-free vaginal tape (n ¼ 117) Colposuspension (n ¼ 97)

Initial hospitalisation

Length of stay in hospital (days) 2.29 [1.9] 6.67 [1.78]

2 {1– 3} 6 {5–8}

Time in anaesthetic room (minutes) 15.7 [8.9] 18.6 [8.9]

15 {10–20} 17 {12– 25}

Time in theatre (minutes) 39.9 [15.4] 51.7 [22.6]

40 {29–48} 50 {35– 60}

Time in recovery area (minutes) 53.4 [41.8] 97.1 [41.2]

45 {31–60} 96 {69– 120}

Return to theatre* 1 (0.85) –

Minutes in theatre 60 –

Use of tension-free vaginal tapes

1 tape 110 (94.02) –

2 tapes 7 (5.98) –

Additional procedures

0 113 (96.59) –

1 4 (3.41) –

Follow up period

Day case visits

0 112 (95.73) 95 (97.94)

1 5 (4.27) 2 (2.06)

Outpatient visits

0 87 (74.36) 74 (76.29)

1– 2 28 (23.93) 21 (21.65)

3– 4 1 (0.85) 1 (1.03)

5– 6 1 (0.85) 1 (1.03)

General practitioner visits

0 77 (65.81) 57 (58.76)

1– 2 30 (25.64) 28 (28.87)

3– 4 6 (5.13) 9 (9.27)

5– 7 4 (3.41) 3 (3.09)

Re-admissions 2 (1.71) 12 (12.37)

Mean length of stay (min– max) 5 (3 –7) 2.6 (1 – 5)

* During initial hospitalisation.

TENSION-FREE VAGINAL TAPE VERSUS COLPOSUSPENSION 257


patients (117 tension-free vaginal tape, 97 colposuspen-

sion). In the sensitivity analysis, the implications of the

missing completely at random assumption for the results of

the analysis were assessed through the use of an alternative

assumption that data were missing at random. This is

equivalent to saying that cases with incomplete data differ

from cases with complete data, but the missing data pattern

is fully predictable from other variables in the data set. On

this basis, we imputed the incomplete values using a

multivariate multiple imputation procedure21 – 23 and con-

ducted a new analysis on the entire data set of 316 patients.

The cost effectiveness of tension-free vaginal tape versus

colposuspension was assessed by relating the mean differ-

ential costs per patient of the two forms of surgery, to their

differential effectiveness in terms of mean QALYs per

patient measured over the six-month follow up period. One

treatment can be defined as more cost effective than its

comparator if one of the following conditions apply: (a) it is

less costly and more effective (i.e. it dominates its compar-

ator); (b) it is more costly and more effective, but its ad-

ditional cost per extra QALY is considered worth paying by

decision-makers; and (c) it is less costly and less effective,

but the additional cost per extra QALY of its comparator is

not considered worth paying by decision-makers. The point

estimates of mean costs and effects can be used to identify

which of these three conditions applies. However, these

means are estimated with uncertainty. Therefore, to account

for uncertainty due to sampling variation, we plotted a cost

effectiveness acceptability curve24 – 27. Given the data col-

lected within the trial, this curve shows the probability of the

tension-free vaginal tape being more cost effective than colpo-

suspension for different levels that the decision-maker may

be willing to pay for an additional QALY28. This is a Bayesian

approach to the presentation of cost effectiveness data29,

although a full Bayesian analysis has not been undertaken.

RESULTS

Table 2 details the main elements of resource use in the

trial. The mean length of stay in hospital with tension-free

vaginal tape was 2.29 days (interquartile range: 1 to 3), as

opposed to 6.67 days with colposuspension (interquartile

range: 5 to 8). Mean time in theatre with tension-free

vaginal tape was 40 minutes (interquartile range: 29 to

48), against 52 minutes (interquartile range: 35 to 60) with

colposuspension. Tension-free vaginal tape patients re-

quired a larger number of resources in terms of additional

surgical procedures and outpatient visits. In the colposus-

pension arm, 12 women (12.4%) were readmitted to hos-

pital by six months follow up, whereas two (1.7%) were

readmitted in the tension-free vaginal tape group.

Table 3. Estimates of mean cost of tension-free vaginal tape compared with colposuspension (UK£). Unless stated, all costs are based on complete cases.

Values are expressed as mean (median) [interquartile range].

Tension-free vaginal tape (n ¼ 117) Colposuspension (n ¼ 97)

Costs

Theatre cost 720 (690) [634 to 754] 437 (422) [343 to 518]

Hospital ‘hotel’ cost 236 (206) [103 to 309] 687 (618) [567 to 824]

Other post-operative cost 28 (0.75) [0 to 4.22] 76 (27) [25 to 30]

Follow up cost at 6 months 74 (46) [0 to 93] 101 (46) [0 to 116]

Total cost per patient 1058 (935) [839 to 1100] 1301 (1195) [1050 to 1449]

Differential costs (tension-free vaginal tape minus colposuspension) �243 [�341 to �201]*

Differential costsy (tension-free vaginal tape minus colposuspension) �242 [�340 to �183]*

* 95% non-parametric confidence interval based on 1000 bootstrap replications: lower band ¼ 2.5 centile; upper band ¼ 97.5 centile.y Based on 316 patients (tension-free vaginal tape ¼ 170; colposuspension ¼ 146), after multivariate multiple imputation.

Table 4. Estimates of mean QALYs of tension-free vaginal tape compared with colposuspension. Unless stated, all results are based on complete cases.

Values are expressed as mean (median) [interquartile range].

Tension-free vaginal tape (n ¼ 117) Colposuspension (n ¼ 97)

EQ-5D values

Baseline 0.778 (0.81) [0.71 to 0.92] 0.785 (0.81) [0.71 to 0.92]

Six weeks 0.788 (0.85) [0.71 to 0.92] 0.754 (0.76) [0.69 to 0.88]

Six months 0.806 (0.85) [0.73 to 0.92] 0.794 (0.85) [0.73 to 0.92]

QALYs 0.397 (0.42) [0.35 to 0.45] 0.387 (0.40) [0.35 to 0.44]

Differential QALYs (tension-free vaginal tape minus colposuspension) 0.010 [�0.010 to 0.030]*

Differential QALYsy (tension-free vaginal tape minus colposuspension) 0.012 [�0.006 to 0.029]*

* 95% non-parametric confidence interval based on 1000 bootstrap replications: lower band ¼ 2.5 centile; upper band ¼ 97.5 centile.y Based on 316 patients (tension-free vaginal tape ¼ 170; colposuspension ¼ 146), after multivariate multiple imputation.

258 A. MANCA ET AL.


Estimated mean costs per patient in the two arms of the

trial are reported in Table 3. Although tension-free vaginal

tape patients had a shorter time in theatre, the associated

cost saving was offset by the cost of tension-free vaginal

tape-specific consumables, which resulted in total theatre

cost being higher in the tension-free vaginal tape arm.

However, when hospital ‘hotel’ costs are also considered,

tension-free vaginal tape is, on average, less costly, due to

the shorter length of hospital stay associated with its use.

This remains the case when other post-operative and follow

up costs are included. The mean total cost per patient was

estimated to be £1058 (interquartile range: £839 to £1100) in

Fig. 1. Bootstrap replications (n ¼ 1000) of the mean differences in costs and QALYs generated from the trial data.

Fig. 2. Cost effectiveness acceptability curve. CCA ¼ complete case analysis (tension-free vaginal tape ¼ 117; colposuspension ¼ 97); MI ¼ multivariate

multiple imputation (tension-free vaginal tape ¼ 170; colposuspension ¼ 146).



the tension-free vaginal tape group and £1301 (interquartile

range: £1050 to £1449) in the colposuspension group. Mean

differential cost of tension-free vaginal tape minus colpo-

suspension was therefore �£243 (95% CI: �£340 to

�£201); that is, a cost saving from tension-free vaginal tape.

Table 4 reports the EQ-5D scores at baseline, six weeks

and six months in the two treatment arms. The mean

QALYs per patient were 0.397 (interquartile range: 0.35

to 0.45) for tension-free vaginal tape and 0.387 (interquar-

tile range: 0.35 to 0.44) for colposuspension. The differ-

ential mean QALYs between the two groups was 0.01 (95%

CI: �0.01 to 0.03).

On the basis of the point estimates of mean cost and

QALYs presented in Tables 3 and 4, tension-free vaginal

tape dominates colposuspension; that is, over six months, it

generates higher mean QALYs and results in lower mean

health service costs. However, mean costs and QALYs are

estimated with uncertainty. This is evident when looking at

Fig. 1, which provides a graphical representation of the

joint distribution of differential mean costs and QALYs

after 1000 bootstrap replications. A simple visual inspec-

tion shows that the simulations fall completely below the

horizontal dotted line on the cost axis. However, a consid-

erable proportion of the simulations falls to the left of the

vertical dotted line on the QALYs axis. In other words, all

the uncertainty in this comparison relates to the mean

difference in QALYs between the two forms of surgery.

Uncertainty in mean costs and outcomes is reflected in

the cost effectiveness acceptability curve shown in Fig. 2.

The continuous line shows the cost effectiveness accept-

ability curve for tension-free vaginal tape for the base-case

analysis. This indicates that the probability of tension-free

vaginal tape being, on average, less costly than colposus-

pension is 100%—this is the point on the curve where the

decision-maker is not willing to pay anything additional for

an extra QALY. The probability of tension-free vaginal

tape being more cost effective than colposuspension is

94.6% when the decision-maker is willing to pay at least

£30,000 per additional QALY. As Fig. 2 shows, even if the

decision-maker is willing to pay up to £100,000 per

additional QALY, the probability that tension-free vaginal

tape is cost effective remains above 85%.

A key determinant of the mean cost saving achieved by

using the tension-free vaginal tape is the difference

between the two procedures in terms of inpatient hospital

stay. A sensitivity analysis was undertaken to investigate the

role of mean differential inpatient stay on (1) the probability

for tension-free vaginal tape of being, on average, cost

saving, and (2) the probability of tension-free vaginal tape

being more cost effective than colposuspension when the

decision-maker is willing to pay £30,000 for an additional

QALY. A visual inspection of Fig. 3 suggests that, all else

being equal, the tension-free vaginal tape is more likely to be

cost saving compared with colposuspension, provided that

the difference in terms of inpatient hospital stay in favour of

the tension-free vaginal tape is not less than two days.

Analogously, when the decision-maker is willing to pay

£30,000 for an additional QALY, the tension-free vaginal

tape is more likely to be cost effective as long as the dif-

ferential inpatient length of stay for women in the tension-

free vaginal tape group is no more than one day higher than

for those women undergoing colposuspension.

Fig. 3. Impact of differential inpatient hospital stay on the probability of the tension-free vaginal tape being, on average, cost saving and cost effective.

— Probability of the tension-free vaginal tape being cost saving as function of the difference in hospital inpatient stay; - - Probability of the tension-free

vaginal tape being cost effective, when the decision-maker is willing to pay £30,000 for an additional QALY, as function of the difference in hospital in

patient stay.

260 A. MANCA ET AL.


Some of the unit costs used in the analysis might not be

representative of those in other UK hospitals. In particular,

the ‘hotel’ cost per inpatient day in hospital will vary

between centres. In order to explore the robustness of the

results to this unit cost, a sensitivity analysis was conducted

varying this cost between £80 and £250 per day. Unsurpris-

ingly, this had little impact on the cost effectiveness results.

Unit costs greater than the base-case value (i.e. £103 per

day) resulted in an even greater mean cost saving for the

tension-free vaginal tape, being the intervention with a

shorter mean length of stay in hospital. Similarly, the

tension-free vaginal tape is still cost saving for a hospital

‘hotel’ cost per day as small as £80.

Finally, a third sensitivity analysis investigated the

impact of missing data on the results of the present study.

The base-case analysis was conducted on the complete case

data set assuming that data were missing completely at

random. An alternative assumption is that data were miss-

ing at random. Under this assumption, multivariate multiple

imputation can be applied to handle the incomplete data

problem. The dotted line in Fig. 2 shows the cost effective-

ness acceptability curve obtained from the analysis of the

entire data set of 316 patients after the application of

multiple imputation. The conclusion of the analysis,

namely, a high probability of the tension-free vaginal tape

being cost effective across a range of willingness to pay

values, remains unaffected.

DISCUSSION

On the basis of the findings presented in this paper over

six months follow up, the tension-free vaginal tape results

in an overall mean cost saving per patient of £243 while

generating a mean improvement in health outcomes of 0.01

QALYs per patient. Although the cost of a tension-free

vaginal tape is markedly higher than the theatre consum-

ables used during colposuspension, this was more than

offset by a reduction in the mean hotel cost of hospital

stay. In this paper, the value for money of the tension-free

vaginal tape was characterised using a cost effectiveness

acceptability curve, which plots the probability of the

tension-free vaginal tape being more cost effective than

colposuspension as a function of the decision-maker’s

willingness to pay for an additional QALY. If decision-

makers are only interested in costs and do not attach any

value to an improvement in patients’ health outcomes, the

probability of the tension-free vaginal tape being cost

effective (i.e. cost saving) is 100%. However, any health

service will value health gain and, although a formal value

for an additional QALY has not been stated explicitly in

this context, it is possible to infer a broad range for this

parameter based on decisions previously taken regarding

what interventions should be funded30,31. Using a wide

range of values for an additional QALY, the probability of

the tension-free vaginal tape being more cost effective than

colposuspension remains appreciably higher than 80%. The

health service will need to decide whether this level of

certainty is sufficient to justify the widespread use of the

tension-free vaginal tape.

Economic evaluation uses a large number of variables

collected over a period of follow up and, in most trials, a

proportion of data is missing. For the base-case analysis,

only observations with complete data were included (62%).

A sensitivity analysis was conducted to explore the impact

of this decision. This showed that using multiple imputa-

tion rather than complete case analysis had little effect on

the results.

The objective of the analysis was to use unit costs which

are representative of UK hospitals. However, there is con-

siderable variation in some costs, in particular, the hotel cost

of an inpatient day in hospital13. The sensitivity analysis

showed that variation in this cost between two extreme

values of £80 and £250 per day (compared with a base-case

of £103) had little impact on the cost effectiveness results.

The difference in the mean length of hospital inpatient

stay between the tension-free vaginal tape and colposus-

pension seems to be a crucial variable in the present study,

and the extent to which the measurement of this variable in

the trial is representative of what would emerge in routine

practice needs to be considered. If the period of time

patients remained in hospital was more a reflection of

clinical expectations than patients’ needs, the estimate of

differential length of stay may be an under- or over-

estimate. Blinding patients and non-surgical clinical staff

to the procedure undergone, as in other surgical trials32,

was not considered feasible here, in view of the differences

in incision and anaesthetic technique. It is possible that

length of stay for both procedures in the trial will become

lower in routine practice over time. The effect of this de-

cline on clinical success rates is unclear. A key finding in

this analysis is that, as long as average length of stay is at

least two days longer following colposuspension, the tension-

free vaginal tape will remain the less costly procedure. Given

the slight QALY gain with the tension-free vaginal tape,

the threshold that would ensure that the tension-free vaginal

tape is the more cost effective (rather than less costly)

procedure will be still lower. Further observation of both

procedures in routine practice is necessary to illuminate this

issue.

One related issue is that, because the trial from which the

data for this economic analysis are obtained is a pragmatic

one, the colposuspension procedure was not standardised

between surgeons. This lack of standardisation among the

14 units involved with the trial will increase the genera-

lisability of the study findings as this permits variation in

clinical practice to be reflected in the cost effectiveness of

the results. The Burch colposuspension undertaken in this

study was open surgery. Some economic comparisons of

this procedure with laparoscopic colposuspension have

been reported33 – 35. However, none of these studies was

undertaken alongside a randomised controlled trial, nor were



they full cost–utility analyses. Further research is required to

assess whether laparoscopic colposuspension can represent a

more cost effective use of resources than the open form of the

procedure and the tension-free vaginal tape.

The costs and benefits estimated here are based on a

period of follow up of six months. As more time elapses

from the point of initial surgery, some women may require

additional treatments for their urodynamic stress inconti-

nence. Further follow up of patients in this trial is essential

to see whether these longer term events have substantive

effect on the results presented here.

In conclusion, the results from this economic evaluation

suggest that, over a post-operative period of six months, the

tension-free vaginal tape is a cost effective alternative to

colposuspension. The results will need to be reassessed on

the basis of longer follow up.

Acknowledgements

The authors would like to thank the UK and Ireland TVT

Trial Group for recruiting patients into this trial. The

authors also thank the patients, technical, secretarial,

nursing and medical staff of the participating hospitals

and the monitoring staff of Ethicon. Ethicon financially

supported this study. The investigators were given

complete freedom to analyse the data and report the results

as they saw fit. Mark Sculpher is also supported by a Career

Award in Public Health funded by the NHS Research and

Development Programme.

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Accepted 6 November 2002

262 A. MANCA ET AL.


a cost–utility analysis of tension-free vaginal tape versus colposuspension for primary urodynamic...

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