Assumptions used in estimating a population benchmark

The assumptions used in estimating an indicative population benchmark rate of 2% per year for referrals into a service providing intrauterine devices (IUDs) and the intrauterine system (IUS) are based on the following sources of information:

• ‘Hospital episode statistics' data to establish the number of fittings of IUDs or the IUS in secondary care per year
• current practice on the numbers of women currently receiving IUDs or the IUS per year
• published research on contraceptive preferences of women in the population
• expert clinical opinion of the topic-specific advisory group, based on experience in clinical practice and literature review.

The topic-specific advisory group advised that the use of IUDs and the IUS are most likely to be indicated in the female population aged 15-54 years. However, the female population aged 15-64 years has been used to calculate the indicative benchmark rate due to the availability of population data at general practice level and its use within the commissioning and benchmarking tool. Commissioners should therefore be aware that the indicative benchmark rate may slightly underestimate the need in females aged 15-54 years.

Activity data - ‘Hospital episode statistics'

The ‘Hospital episode statistics' (HES) database contains details of all admissions to NHS hospitals in England. It includes private patients treated in NHS hospitals, patients who were resident outside England and care delivered by treatment centres (including those in the independent sector) funded by the NHS.

IUDs and the IUS are usually fitted in GP surgeries or community contraceptive services, but they can also be fitted in secondary care. Analysis of 2005/06 HES data suggests that the annual rate of fittings of IUDs and the IUS in secondary care was around 0.08%, or 80 per 100,000, of the female population aged 15-54 years. This figure is based on episodes where the fitting of an IUD or the IUS was either for contraception (in around 10% of cases, that is 0.01%) or for the management of heavy menstrual bleeding (HMB), including after a hysteroscopy (approximately 0.07%).

The topic-specific advisory group advised that a proportion of these fittings could probably be carried out in community settings - for example, general practices and community contraceptive services. Fittings of IUDs or the IUS following a termination of pregnancy have been excluded as these data are not presented in the commissioning and benchmarking tool for data governance reasons, and care of these individuals is usually via a different care pathway.

Current practice

Prescribing

There has been an increase of around 60% in the prescribing of the IUS in primary care in England between February 2003 and July 2007 (see figure 1). However, there remains a large variation in the prescribing of IUDs and the IUS within the community that may not be accounted for by differences in population and choice of contraception.

General practice data

Data were extracted from IMS Disease Analyser and the Doctors' Independent Network Database, which hold data on a sample of GP practice databases, to determine the following for England.

• Annual diagnosis rate of HMB within primary care. The analysis suggests that this is around 2.71% of the female population aged 15-54 years.
• Annual prescribing rate of the IUS to women with HMB. The analysis suggests that around 13% of women aged 15-54 years who were diagnosed with HMB were prescribed the IUS for the management of HMB between September 2006 and August 2007. Therefore the annual prescribing rate of the IUS to the female population aged 15-54 years for the management of HMB is 0.35%. However, there is evidence^[1] that pharmaceutical management of HMB may not be optimal and that increases in the prescribing of the IUS for the management of HMB could be anticipated.
• Annual prescribing rate of IUDs and the IUS to women without HMB (that is, for contraception). The analysis suggests that IUDs and the IUS represent over 4% of current annual prescribing for contraception. This equates to around 0.79% of the female population aged 15-54 years being prescribed IUDs or the IUS for contraception per year.

The figure of 0.79% is likely to be an underestimate of true prescribing levels of IUDs and the IUS because some women are prescribed IUDs or the IUS within specialist community contraceptive services. The ‘Findings of the baseline review of contraceptive services in England' in 2007 suggests that, on average, around 25% of women who use contraceptive services attend specialist community contraceptive services, and the estimated level of prescribing long-acting reversible contraception (LARC) within these services is 20% of the total contraceptive prescribing, compared with 14% in general practice. Therefore the prescribing of IUDs and the IUS within general practice represents around 68% of the total prescribing of IUDs and the IUS within the community. Adjusting the figure of 0.79% (the annual level of prescribing within general practice) to account for prescribing in the community as a whole means that 1.16% of women aged 15-54 years are prescribed an IUD or the IUS for contraception in the community per year.

Therefore, 1.59% of women aged 15-54 years are prescribed IUDs or the IUS per year. This comprises the 0.08% of women having an IUS or IUD fitted in secondary care for HMB or contraception, 0.35% prescribed for the management of HMB in primary care and 1.16% prescribed for contraception, in the community, per year. This is current practice and may not represent best practice.

The assumptions used in estimating the current level of annual prescribing of IUDs and the IUS will be reviewed when new data and sources of information become available.

Published research

Armstrong and Donaldson (2005)^[2] used consensus methods to arrive at an ideal profile of contraception provision. Their research looked at relative proportions of all prescribable methods of contraception. The findings relating to IUDs and the IUS have been applied to the age specific rates of those being prescribed contraception in general practice in a year (see table 1). We have assumed that the overall numbers of women using contraception have remained the same.

Armstrong and Donaldson did not provide estimates on contraception use for women over 49 years, so the estimate for the 45-49 years age band has been applied to the 50-54 years age band also (see table 1).

Table 1. Optimal proportion of women receiving IUDs or the IUS in primary care in England

Applying the expected preference for IUDs and the IUS to the populations aged 15-54 years currently receiving medical contraception, 22% of women receiving medical contraception may choose to use an IUD or the IUS. This equates to 4.84% of all women aged 15-54 years.

The figure of 4.84%, however, may be an underestimate as the age specific populations that the preferences have been applied to relate only to those in general practice. Therefore it has been adjusted to account for the estimated 25% of women receiving contraception in specialist community contraceptive services giving a figure of 6.45% for women aged 15-54 years.

Furthermore, the NICE cost impact report for CG30 on long-acting reversible contraception notes that the average duration of use of IUDs and the IUS is around 3 years, and therefore the figure of 6.45% does not represent the expected annual prescribing rate.

Expert clinical opinion

The topic-specific advisory group advised the following.

• The NICE cost impact report for CG30 on long-acting reversible contraception notes that more women will choose a LARC method if they are given better information and improved access to all methods of contraception. Commissioners need to be aware that this is central to moving towards the benchmark rate offered.
• Based on clinical practice, a 15-20% increase in the current annual prescribing rate of IUDs and the IUS (1.59%) might be expected.
• Commissioners should examine local prescribing patterns of IUDs and the IUS, as well as of implants and injections, to ensure that women are given a choice of contraception methods.
• Commissioners should examine local referral patterns, prescribing practice, referral rates into secondary care and differences in local populations to ensure that women with HMB receive optimal care.

Conclusions

Based on the data from current practice and other information outlined above, it is concluded that around 2% of the female population aged 15-54 years may require an IUD or the IUS per year. This is based on the following assumptions:

• The current annual prescribing rate of IUDs and the IUS for contraception in specialist community contraceptive services and general practice is around 1.16% of the female population aged 15-54 years, and rates will continue at or above this level.
• 0.35% of the female population aged 15-54 years per year are currently prescribed the IUS for the management of HMB in general practice. While this represents current practice it may not be best practice, and it is therefore the minimum level of prescribing that can be expected.
• The current national level of IUD and IUS fitting in secondary care for the management of HMB and for contraception (not including fittings post termination of pregnancy) is around 0.08%, of which a proportion could be moved into the community.
• It is not possible to determine what proportion of women had an IUD or the IUS both prescribed and subsequently fitted within general practice. However, it is assumed that each prescription represents identified need. Therefore the figures of 0.35% (prescribed for HMB) and 1.16% (prescribed for contraception) have been added to the rate of fittings of IUDs and the IUS in secondary care (0.08%) to determine the current level of prescribing/fitting of IUDs and the IUS of 1.59%.
• Optimally around 6.45% of the female population aged 15-54 years could use IUDs or the IUS as a preferred contraceptive method.
• Taking into account the expected 15-20% increase in prescribing/fitting from the current rate of 1.59% suggested by the topic-specific advisory group means that the annual prescribing/fitting rate could be around 1.98% per year.
• Optimally the proportion of women who could be prescribed an IUD or the IUS for contraceptive purposes is around 6.45% of the female population aged 15-54 years, which, when divided by the average duration of use of an IUD or the IUS (3.34 years) gives an annual prescribing rate for IUDs or the IUS of 1.93%. Adding to this the annual prescribing rate of the IUS for the management of HMB in primary and secondary care (around 0.35% and 0.07%, respectively), the annual requirement for IUDs and the IUS could be around 2.35% per year
• The mid-point of the estimate suggested by the topic-specific advisory group and published research on the ideal profile of contraception provision is 2.15% per year.

Therefore the population benchmark for the service requirement for IUDs and the IUS is estimated to be around 2% per year. This represents the numbers of women who may require IUDs and the IUS across primary and secondary care for contraception and in the management of HMB. It includes those women who require either new fittings or re-fittings in a year.

Commissioners should ensure that there is appropriate access to services for IUDs and the IUS, and monitor choice and uptake of LARC methods of contraception for both HMB and for contraception. Commissioners may wish to review these planning assumptions in the commissioning and benchmarking tool to meet local population and service needs. In addition, commissioners will need to take into account the variable time in situ of different IUDs and the IUS.

Because some fittings of IUDs and the IUS in secondary care have been included in the benchmark, commissioners will need to be aware that some of these fittings will need to continue to be performed in secondary care, but others could be performed in the community.

Use the IUDs and the IUS commissioning and benchmarking tool to determine the level of service that might be needed locally and to calculate the cost of commissioning the service using the indicative benchmark and/or your own local data.

References

1. Rahman KM, Onyeka BA (2001) Treatment of menorrhagia before hysterectomy in a district general hospital. A retrospective review. Journal of Obstetrics and Gynaecology 21: 64-6.

2. Armstrong N, Donaldson C (2005) The economics of sexual health. Newcastle: University of Newcastle upon Tyne.