Assumptions used in estimating a population benchmark

The assumptions used in estimating a benchmark for the surgical management of otits media with effusion (OME) in children are based on the following sources of information:

• epidemiological data on the prevalence of OME
• activity data to establish the current rate of surgery
• expert clinical opinion of the topic-specific advisory group, based on experience in clinical practice and literature review.

Epidemiological data

Currently there is limited availability of epidemiological data on which to estimate the optimal rate of surgical management of OME in children.Therefore it has not been possible to develop a benchmark based on the prevalence, severity and persistence of OME in children.

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. The classification system used to code procedures within HES is the Office of Population, Censuses and Surveys: classification of interventions and procedures, 4th revision (OPCS4).

For the purpose of determining this benchmark for the surgical management of OME, we have used HES data extracted on the basis of the OPCS4 code D15.1: myringotomy with insertion of ventilation tube (grommet) through the tympanic membrane. Data have been extracted where the code occurs either as the main procedure or in one of the 14 secondary procedure fields. In a proportion of cases, insertion of ventilation tube may occur alongside other procedures for example adenoidectomy. Restricting the analysis to data for coding only under the main procedure significantly underestimates activity levels and overestimates regional variations in rates.

Please note: all following mentions of rate(s) per 100,000 children refer to the rate(s) per 100,000 children under the age of 12 years.

Analyses of the data indicate that the rate of procedures has decreased significantly since the early 1990s. There has been a decrease in rates from around 700 per 100,000 children in 1989/90 to around 400 per 100,000 children in 2006/07. This is an overall decrease in procedures of around 40%. This may be linked to information published in the early 1990s that questioned the use of ventilation tubes^[1]. The rate of decline has slowed in more recent years (see figure 1).

The mean directly age-standardised rate of surgery for all primary care organisations in England in 2006/07 is 400 per 100,000 children. This estimated standardised rate of surgical management of OME is higher than the estimate used in the NICE costing report on surgical management of OME. This is because the costing report used data based on the coding of the procedure as the main procedure.

Figure 2 is a funnel plot that shows the variation in the directly age-standardised rates of surgery across England in 2006/07. Rates vary by primary care organisation from around 100 per 100,000 children to 800 per 100,000 children. Thus there is over an eightfold difference in rates across England.

Smoking among parents and/or carers is a risk factor for OME in children^[2]. Some of the variation in rates observed may be related to the prevalence of smoking but there are likely to be other factors involved, such as referral criteria and service capacity. Clinical experts have suggested that those primary care organisations with very high or very low rates of procedures may not be operating within expected referral criteria.

It is not expected that the mean rate of surgery nationally should change significantly with the implementation of the NICE clinical guideline CG60 on surgical management of OME. Therefore, the current rate of surgical management of OME based on the national average of 400 per 100,000 children under the age of 12 years per year is considered appropriate as an indicative benchmark. Commissioners may wish to benchmark their activity against this figure and age-adjusted rate of their neighbouring or other primary care organisations. Directly age‑standardised rates of surgery for all primary care organisations can be found in table 1.

Expert clinical opinion

The topic-specific advisory group suggests, based on emerging research, that on average, children with OME in England are likely to be receiving surgical intervention appropriately, and hence support the indicative benchmark of 400 per 100,000 children under the age of 12 years based on the national average.

Commissioners should take into account parental smoking because areas with a higher than average prevalence of smoking may have a greater need for surgical management of OME in children.

Conclusions

Based on the data above, it is considered that a benchmark rate for surgical management of OME is 0.4%, or 400 per 100,000, children under the age of 12 years per year is appropriate. This is based on the following assumptions:

• the national mean rate of surgical management of OME is around 400 per 100,000 children per year
• there may be areas with rates of surgery that may need to increase or decrease; the mean average rate nationally is not likely to change significantly with the implementation of the NICE clinical guideline CG60 on surgical management of OME

Therefore the benchmark for surgical management of OME is estimated to be approximately 0.4%, or 400 per 100,000, children under the age of 12 years per year.

Use the service for the surgical management of otitis media with effusion in children commissioning 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 Black N, Hutchings A (2002) Reductions in the use of surgery for glue ear: did national guidelines have an impact? Quality and Safety in Health Care 11:121-4.

2 Collet JP, Larson CP, Boivin JF et al (1995) Parental smoking and risk of otitis media in pre-school children. Canadian Journal of Public Health 86: 269-73.