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Assumptions used in estimating a population benchmark

Several assumptions have been used to estimate the population benchmark for adults requiring biologic drugs for the treatment of inflammatory disease in rheumatology, dermatology and gastroenterology, of 0.19% or 190 per 100,000 adult population per year. These assumptions are based on the following information sources:

  • epidemiological data on the number of people with rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis,psoriasis, Crohn's disease and ulcerative colitis. The benchmark was developed using the expert clinical opinion of the topic-specific advisory group, based on experience in clinical practice, audit and published literature.
  • activity data procedure codes associated with high cost drugs.

For the purpose of this commissioning guide the adult population aged 18 years or older in England has been used except where specified.

Epidemiological data

This commissioning guide focuses on the use of biologic drugs for the treatment of inflammatory disease in rheumatology, dermatology and gastroenterology.

The conditions included in the population benchmark are adults needing biologic drugs for the treatment of the following inflammatory conditions: rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, psoriasis, Crohn's disease and ulcerative colitis. It has been assumed that the number of patients discontinuing treatment each year is approximately equal to the numbers of new patients starting treatment, unless otherwise stated.

Commissioners should take into account local circumstances to determine the number of patients eligible for and receiving biologic drugs for the treatment of inflammatory disease. A sensitivity analysis for the number of patients receiving biologic drugs is available in the commissioning and benchmarking tool.

People aged 18 years and older

Rheumatoid arthritis

Rheumatoid arthritis is a chronic long-term inflammatory disease. The use of biologic drugs for treating rheumatoid arthritis has been increasing in recent years and is now levelling off in some areas.

The prevalence of rheumatoid arthritis in England is 0.86%[1] of the adult population or around 350,000 people. It is estimated that around 10%[2] of people with rheumatoid arthritis will be eligible for and receiving biologic drugs. This equates to around 35,000 people in England.

Available data suggests that the indicative benchmark rate for the number of people with rheumatoid arthritis eligible for and receiving treatment with biologic drugs is 0.086%, or 86 per 100,000 adults aged 18 years or older per year.

Ankylosing spondylitis

Ankylosing spondylitis is a disease that causes inflammation mainly in the lower spine, which results in back pain and stiffness. It affects around 70,000 people in England[3], and around 20,000 of these will be eligible for treatment with biologic drugs[2].

Expert clinical opinion suggests that biologic drugs may not be the most appropriate treatment for all eligible patients. According to expert clinical opinion 30%[2], or around 6,800 of the 20,000 eligible patients will take up treatment.

Available data suggests that the indicative benchmark rate for the number of people with ankylosing spondylitis receiving treatment with biologic drugs is 0.017%, or 17 per 100,000 adults aged 18 years or older per year.

Psoriatic arthritis

Psoriatic arthritis is a unique inflammatory arthritis associated with psoriasis[4]. Because of the problems in definitively diagnosing psoriatic arthritis, there are few studies on the incidence and prevalence of the disease. The results vary widely depending on the cohort studied and the diagnostic criteria used, ranging from 0.3% to 1%[5] of the population. This is examined further in the commissioning and benchmarking tool.

For the purpose of this benchmark a midpoint of prevalence of 0.65% has been used. This equates to around 260,000 adults in England with psoriatic arthritis. The proportion of prevalent patients receiving treatment with a biologic drug is estimated to be around 2.4%[6] or around 6,200 people.

Available data suggest that the indicative benchmark rate for the number of people with psoriatic arthritis eligible for and receiving treatment with biologic drugs is 0.016% or 16 per 100,000 adults aged 18 years or older per year.

Psoriasis

Psoriasis is common in the population and effects around 600,000 or 1.5%[4] of adults in England.

There is debate around the proportion of these patients who are eligible for and receiving treatment with a biologic drug, ranging from 1.1% to 5%[2][7][8]. This is examined further in the commissioning and benchmarking tool. It should be noted that expert clinical opinion suggests that, because of the nature of the condition, not all patients eligible for biologic treatments will currently be identified and treated with them.

For this benchmark the proportion of prevalent patients eligible for treatment with a biologic drug is estimated to be around 3%[2] or 18,000 people. A small proportion of patients will also have psoriatic arthritis and be eligible for treatment for both their psoriasis and psoriatic arthritis.

Available data suggest that the indicative benchmark rate for the number of people with psoriasis eligible for and receiving treatment with biologic drugs is 0.045%, or 45 per 100,000 adults aged 18 years or older per year.

Crohn's disease

Crohn's disease is a chronic inflammatory condition affecting the gastrointestinal tract. People with Crohn's disease have acute exacerbations of the symptoms in between periods of remission or less active disease. Around 80,000[9] adults in England have Crohn's disease.

It is estimated that a total of around 13% or 10,500[2][9] adults will have severe active Crohn's disease or fistulising Crohn's disease and be eligible for treatment with biologic drugs. These are patients who are either intolerant to conventional therapy or for whom conventional therapy has failed.

Available data suggest that the indicative benchmark rate for the number of people with Crohn's disease eligible for and receiving treatment with biologic drugs is 0.026%, or 26 per 100,000 adults aged 18 years or older per year.

Ulcerative colitis

Ulcerative colitis is a form of colitis, a disease of the large intestine or colon. Ulcerative colitis is an intermittent disease, with periods of exacerbated symptoms, and periods that are relatively symptom-free.

There are approximately 76,000[10] people in England with ulcerative colitis. Of these, an estimated 6%[2] (5000) have an acute exacerbation of severely active ulcerative colitis per year. It is estimated that 15%[2] (750) of these patients would receive treatment with a biologic drug.

Available data suggest that the indicative benchmark rate for the number of people with ulcerative colitis receiving treatment with biologic drugs is 0.001%, or 1 per 100,000 adults aged 18 years or older per year.

People under 18 years of age

Juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is a relatively rare disease, with an estimated incidence in the UK of 0.1 per 1000 children, equivalent to 1000 new cases per year. The prevalence is in the order of 1 per 1000 children, so about 8,500 children in England are affected[11]. This equates to around 1,200 children who are eligible for and receiving treatment with biologic drugs[11].

Children have been defined here as aged between 4 and 17 years. This benchmark does not include the small number of people aged 18 or older with long-standing JIA who are receiving treatment with biologic drugs.

Available data suggest that the indicative benchmark rate for the number of children aged 4-17 years with JIA eligible for and receiving treatment with biologic drugs is 0.015%, or 15 per 100,000 children per year.

Crohn's disease

Around 1,800 children aged between 6 and 17 years in England have Crohn's disease.

Using the methodology applied above for adult Crohn's disease, it is estimated that a total of around 13% or 240 children will have severe active Crohn's disease or fistulising Crohn's disease and be eligible for biologic drugs. These are patients who are either intolerant to conventional therapy or for whom conventional therapy has failed.

Available data suggest that the indicative benchmark rate for the number of children with Crohn's disease eligible for and receiving treatment with biologic drugs is 0.003%, or 3 per 100,000 children, per year.

Activity data

Biologic drugs are often administered to patients with a moderate or severe form of a long-term inflammatory condition, who may be at high risk of hospital admission because of exacerbations of the disease. Commissioners may wish to track patients who are currently receiving high cost drugs, such as biologics, to show the level of activity in secondary care. This may be compared with activity without the use of high cost drugs such as biologics. The commissioning and benchmarking tool contains a data specification for the conditions mentioned in this guide and the OPCS4 procedure codes associated with high cost drugs.

Conclusions

Based on the epidemiological data and other information outlined above, it is concluded that the population benchmark for adults aged 18 years or older requiring biologic drugs for the treatment of inflammatory disease in rheumatology, dermatology and gastroenterology is 0.19%, or 190 per 100,000 adult population, per year.

In addition, 0.015%[9], or 15 per 100,000, children aged 4-17 years will also be eligible and receiving biologic drugs for the treatment of JIA. A further 0.003%, or 3 per 100,000, children aged 6-17 years will be eligible and receiving biologic drugs for the treatment of Crohn's disease.

This is based on the following assumptions in the table below.

Assumptions used in estimating the population benchmark for adults requiring biologic drugs for the treatment of inflammatory disease

Condition Estimated number of people with the condition Estimated number of people with the condition eligible and receiving treatment with biologic drugs Estimated percentage of people with the condition eligible and receiving treatment with biologic drugs
Rheumatoid arthritis 350,000 35,000 10.0%
Ankylosing spondylitis 71,000 6,900 9.7%
Psoriatic arthritis 263,000 6,300 2.4%
Psoriasis 607,000 18,000 3.0%
Crohn's disease (adults) 81,000 10,500 13.0%
Ulcerative colitis 77,000 750 1.0%
Juvenile idiopathic arthritis 8,500 1,300 15.0%
Crohn's disease (children) 1,800 240 13.0%

Use the Determining local service levels for biologic drugs for the treatment of inflammatory disease 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. Symmons D, Turner G, Webb R et al. (2002) The prevalence of rheumatoid arthritis in the United Kingdom: new estimates for a new century. Rheumatology 41: 793-800

2. Sensitivity analysis, in commissioning and benchmarking tool

3. Keat A, Barkham N, Bhalla A et al. (2005) BSR guidelines for prescribing TNF-alpha blockers in adults with ankylosing spondylitis. Report of a working party of the British Society for Rheumatology. Rheumatology 44: 939-47

4. Gelfand J, Weinstein R, Porter S et al. (2005) Prevalence and treatment of psoriasis in the United Kingdom: a population-based study. Archives of Dermatology 141: 1537-41

5. Gladman D, Antoni C, Mease P et al. (2005) Psoriatic arthritis: epidemiology, clinical features, course, and outcome. Annals of the Rheumatic Diseases 64(2): ii14-7

6. National Institute for Health and Care Excellence (2006) Etanercept and infliximab for the treatment of adults with psoriatic arthritis. NICE technology appraisal guidance 104 (replaced by TA199 August 2010).

7. National Institute for Health and Care Excellence (2008) Infliximab for the treatment of adults with psoriasis: Costing template and report. NICE technology appraisal guidance 134

8. Eedy D, Burge S, Potter, J et al. (2008) An audit of the provision of dermatology services in secondary care in the United Kingdom with a focus on the care of people with psoriasis. British Association of Dermatologists. Available from: www.bad.org.uk/Portals/_Bad/Audits/BAD%20Psoriasis%20Audit%2018.02.08.pdf

9. National Institute for Health and Care Excellence (2010) Infliximab (review) and adalimumab for the treatment of Crohn's disease (including a review of technology appraisal guidance 40): Costing template and report. NICE technology appraisal guidance 187

10. National Institute for Health and Care Excellence (2008) Infliximab for subacute manifestations of ulcerative colitis. NICE technology appraisal guidance 140

11. National Institute for Health and Care Excellence (2002) Guidance on the use of etanercept for the treatment of juvenile idiopathic arthritis. NICE technology appraisal guidance 35

This page was last updated: 16 October 2012

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Copyright 2014 National Institute for Health and Care Excellence. All rights reserved.