Colposcopy clinic cost-effectiveness
model for use by colposcopy clinics
in England
1. Background
The School of Health and Related Research (ScHARR) at the University of Sheffield
was commissioned by the NHS Cancer Screening Programme to produce a model to
evaluate the cost-effectiveness of the change to mild referral guidelines to individual
colposcopy clinics in England, and to assess the cost-effectiveness of different local
strategies following the change to mild referral guidelines. This model is based on two
previous models: a cost-effectiveness model for the use of LBC in England (Karnon
et al., Liquid-based cytology in cervical screening: an updated rapid and economic
analysis; Health Technology Assessment 2004; Vol. 8: No. 20) and a colposcopy
capacity model that calculates the increase in workload after changes of the
management for mild dyskariosis results (Eggington et al., Modelling the impact of
Referral Guideline Changes for Mild Dyskariosis on Colposcopy Services in England;
NHSCSP publication No. 24, October 2006). This model is a modification of the LBC
cost-effectiveness model and incorporates the different local policy options of the
capacity model. The model was designed for individual colposcopy centres to
estimate the cost-effectiveness of their policies, current and future, in order to
accompany the capacity model.
1.1 The current model
The model has now been updated to include HPV triage testing as HPV testing has
now become part of the screening pathway. Colposcopy centres can now estimate the
effect of including HPV testing on the clinical effectiveness of the Screening
Programme. This user manual has been produced in order to facilitate the use of the
Colposcopy Clinic Cost Effectiveness Model.
2. Using the model
2.1 Model requirements
The model has been produced in Excel and requires the user to:
(1) Choose from a number of current and future policy options
(2) Enter information about the local patient population and clinic organisation.
2.2 Evaluating the cost-effectiveness of the policies
To evaluate the cost-effectiveness of the strategies of your colposcopy department as
a result of policy changes:
(1) Open the workbook named ‘ScHARR Colposcopy Clinic Effectiveness Model’
and Enable the macros.
[Macros are programming sequences that allow specified tasks within the model
to occur automatically. In the model there are a few macros to provide the results
faster and in a more-user friendly way. They do not contain viruses and are safe
to ‘enable’ within Excel.
(2) Excel should open on the ‘Choice’ worksheet.
(3) Fill in all details on this sheet using the drop-down menus for the ‘management
policy’ section and by filling in appropriate figures for the ‘treatment policy’,
‘Population and coverage’ and ‘Patients attendance’ sections below. Where this
data is not available we would recommend the use of the default data displayed.
(4) Click on ‘run these policies’ to the right of the options. This should produce a
table of results (explanation of results’ table in Section 3 of this manual). Please
not it may take a few minutes for the model to run and the results to be displayed
during which time excel will be unresponsive.
If an error message appears on the screen saying all the textboxes are not filled
whereas they are, close the excel file and re-open it. It should work properly this time.
(5) Wait for a few seconds and then the sheet ‘Results’ appears.
2.3 Definitions and notes regarding model inputs
2.3.1 Management policy
Please choose the description in the pull down menus, which most closely match your
current and future policies as described below.
‘Screening type’: select the nature of the screening test for cervical cancer (liquidbased cytology only or HPV triage) before and after the change.
‘Post-treatment screening type’: select the nature of the screening follow-up
following treatment, either current guidelines which includes annual testing following
treatment for CIN2 or 3 or HPV ‘test of cure’.
‘Mild dyskaryotic smear referral policy’: This option is to allow the clinics to test
the referral guideline changes to colposcopy referral (NHSCSP publication 20 April
2004). The local policy may be that a patient can be referred to colposcopy after one
or two consecutive mild smear results. If the option ‘refer to colposcopy after 2 mild
smears’ is chosen, then a patient who has a mild smear result at a routine call is
rescreened 6 months later. If she obtains a second consecutive mild result or a
moderate or severe result, then she is referred to colposcopy.
‘Borderline smear referral policy’: The local policy may be that a patient can be
referred to colposcopy after 2 or 3 consecutive borderline smear results taken at sixmonthly intervals.
‘CIN1 management policy’: Three options are available for the patients who have a
CIN1 result at colposcopy. Patients may be discharged from colposcopy, seen at six
monthly intervals for colposcopy assessment (for some specified time period), or
treated at diagnosis.
‘CIN1 time-to-treat policy’: This option is only available if the strategy ‘Repeat
colposcopy at 6-monthly intervals’ above is chosen. In this case you need to define
the duration of the follow-up for the patients having CIN1 persistent results. The
choice available is for 1, 2, 3 or 4 repeat colposcopies corresponding to a period of
follow-up of 6, 12, 18 or 24 months.
‘Treatment policy (low-grade patients, CIN1)’: This option is available if women
having a CIN1 result at colposcopy are treated. You have only two options: a “See
and Treat” appointment or a “Treat later” policy, which includes a diagnostic
colposcopy and a separate treatment appointment at a later date.
‘Treatment policy (high-grade patients)’: This option is for the management of the
women obtaining CIN2 or CIN3 at colposcopy. The model assumes that these patients
are always treated; however patients may have a “See & Treat” appointment or a
"Treat later" policy.
2.3.2 Population and coverage data
Please fill in according to the population the clinic covers as described below.
1) Screening coverage (% of eligible women having screening smear in the
appropriate screening interval);
2.3.3 Patient attendance data
Please fill in according to the population the clinic covers as described below.
The three attendance data categories should be filled in to reflect the attendance rates
at the three following different kinds of appointment (first appointment, follow-up
colposcopies, and treatment).
For Post-treatment policies and population and coverage, default figures are suggested
in the userform. These are national average figures. They are an example of the types
of figures required. These can be applied if you do not have access to the true figures
required.
3. Explanation of model results
3.1 Overview
A summary of the key output figures is presented; Total cost for the population served
by the clinic and Total Life Years (LYs) and Quality-Adjusted Life Years (QALYs)
for the population served by the clinic. A comparison of these figures between the
current and the future policies is presented. A discount of 3.5% is applied to all costs
and health utility values within the model.
The ICER value is also given. However, this may be blank if the intervention is both
cost saving and increases the number of QALYs as the policy will be considered costeffective.
The next set of results is a qualitative interpretation of the difference in costs and
efficacy between the two policies, indicating any improvements in the future policy.
Finally, the increase/ decrease in the rate of detection of high-grade disease cases is
presented as a result of the future policies in comparison to the current policies. The
largest impact in terms of cost implications within the screening programme is also
displayed.
3.2 Definition of Life Year, QALY and ICER:
Life Years are a measure of benefit of health care. It corresponds to the average life
expectancy of a patient from the age of entry to the simulation, which in the model is
15 years old. In the results shown, the number of expected life years is discounted by
3.5% each year. This means that less weight is placed on future benefits than on
present benefits of the policies and hence the number of life years calculated by the
model is lower than the normal life expectancy of a woman in the United Kingdom.
Discounting is a standard methodology within health economic models and is
recommended by the National Institute for Health and Clinical Excellence (NICE).
QALYs, Quality–Adjusted Life Years, are another measure of benefit of health care
calculated by adjusting the expected life years for expected quality of life of the
patient. The QALYs presented in the results are also discounted at 3.5%.
The incremental cost-effectiveness ratio (ICER) is the unit used by NICE to determine
cost-effectiveness. Interventions with an ICER under £30,000 per QALY are
generally considered to be cost-effective. The ICER is calculated by dividing the
difference between the total costs between the two interventions by the difference in
total QALYs.
3.3 Contact details for further information
Please contact a.r.bessey@sheffield.ac.uk for any queries about this model.