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| Cost-effectiveness of advising the use of topical or oral ibuprofen for knee pain: the TOIB study [ISRCTN: 79353052] |
| Castelnuovo E, Cross P, Mt-Isa S, Spencer A, Underwood M |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. CRD summary This study determined the cost-effectiveness of oral versus topical non-steroidal anti-inflammatory drugs for the treatment of knee pain in older people. The authors concluded that oral ibuprofen might be preferred to topical ibuprofen in selected patients, but the uncertainty on the cost-effectiveness of this finding was highlighted. On the whole, the study was well conducted and addressed many areas of uncertainty. The authors' conclusions are likely to be valid. Type of economic evaluation Study objective The objective was to determine the cost-effectiveness of oral versus topical non-steroidal anti-inflammatory drugs (NSAIDs) for the treatment of knee pain in patients aged 50 years or older. Interventions The NSAID studied was ibuprofen and topical ibuprofen was compared with oral ibuprofen. Methods Analytical approach:This economic evaluation was based on data from a single study. The two time horizons considered were 12 and 24 months. The authors stated that the perspectives of both the National Health Service (NHS) and society were adopted.
Effectiveness data:The clinical data were derived from the Topical or Oral Ibuprofen (TOIB) study which recruited 585 patients aged 50 years or older who had received treatment for chronic knee pain from 26 Medical Research Council General Practice Research Framework practices spread across the UK. Specifically, 282 participants were enrolled in a randomised controlled trial (RCT) and 303 in a patient preference study. The length of follow-up was 24 months. The key clinical outcome was patients’ preference (measured by health utilities, and dependent on the side effects) for oral or topical treatment.
Monetary benefit and utility valuations:The utility valuations were derived from the samples of patients recruited to the RCT and to the preference study. Details of the derivation of these values were provided and the EuroQol at five dimensions (EQ-5D) was used to obtain the utility weights. Assessments took place at baseline, three, six, 12, and 24 months.
Measure of benefit:Quality-adjusted life-years (QALYs) were used as the summary benefit measure. QALYs accrued in the second year were discounted at an annual rate of 3.5%.
Cost data:The cost items were primary care and outpatient consultations, physiotherapy services, diagnostic tests, hospital admissions, prescriptions, hospitalisations, equipments, domiciliary help, and other aids. These items were included regardless of whether they were paid for by patients or by the health care system. Thus, privately purchased services were included to reflect the societal perspective. Productivity losses were not included as most of the patients were retired. The resource use was taken directly from the RCT and the preference study, using participant questionnaires. The health care costs were derived from official NHS sources such as the Reference Costs Database and the Prescription Cost Analysis Database. The private costs were based on patients’ expenses. All costs were in UK pounds sterling (£) and the price year was 2005. A 3.5% annual discount rate was applied to costs incurred during the second year of treatment.
Analysis of uncertainty:: Non-parametric bootstrapping was carried out in order to investigate whether the estimated costs, QALYs, and cost-utility ratios were robust. Cost-effectiveness acceptability curves (CEACs) were generated for willingness to pay for a QALY thresholds of between £0 and £40,000. A deterministic sensitivity analysis was also carried out on unit costs, the cost of admission, and the discount rate. Finally, the expected value of perfect information (EVPI) was calculated for two eligible populations, which were all individuals in the UK reporting moderate and severe knee osteoarthritis (OA), and 60% of all individuals with knee OA. Results The differences in QALYs between the groups did not reach statistical significance. However, there was a trend towards fewer QALYs in the topical group over both the 12- and 24-month horizons. Specifically, the oral group experienced an incremental gain over the topical group of 0.021 QALYs over 12 months and 0.038 over 24 months, in the RCT, whilst in the preference study, they incrementally gained 0.028 QALYs over 12 months and 0.037 over 24 months.
From the NHS perspective, topical ibuprofen compared with oral ibuprofen saved £191.4 over 12 months and £455.1 over 24 months, in the RCT, and £71.8 over 12 months and cost an additional £33.1 over 24 months, in the preference study. Thus, the incremental cost per QALY gained was £9,114 over 12 months and £11,976 over 24 months, in the RCT, and £2,564 over 12 months, in the preference study, while the oral formulation was dominant over 24 months. Similar findings were achieved when a societal perspective was adopted.
The deterministic sensitivity analysis did not substantially alter the base-case findings. The CEACs indicated that the probability of considering oral ibuprofen cost-effective over 12 months approached 80% at a threshold of £30,000 per QALY in the RCT and at a threshold of £20,000 in the preference study. The EVPI highlighted the high degree of uncertainty about the preferred treatment. For example, using RCT data the EVPI, over 10 years, ranged from £170 million to £1,000 million, at 12 months, and from £1,000 million to £6,000 million, at 24 months. Authors' conclusions The authors concluded that oral NSAIDs might be preferred to topical ones in selected patients, but the EVPI analysis revealed the uncertainty around the cost-effectiveness of this finding. CRD commentary Interventions:The selection of comparators was appropriate in that two administration options for the same drug were considered.
Effectiveness/benefits:The clinical data were obtained from the direct analysis of patients enrolled in two studies. Despite similar baseline characteristics, slightly different findings were achieved. Little information on the methodology of the two clinical studies was provided as the authors referred to original publications. The length of follow-up appears to have been appropriate. The derivation of the benefit measure was described. QALYs are a validated benefit measure, which allow cross-disease comparisons and which capture the impact of the intervention on quality of life, which is a relevant measurement of health for patients with chronic knee pain.
Costs:: Two separate perspectives were used, which provides useful information for different payers. A breakdown of cost items was provided, although detailed information on the resource use and unit costs was presented in an online appendix. The resource use reflected the actual consumption of resources in the real-world setting. The authors justified the exclusion of costs related to productivity losses on the grounds that most of the patients were retired. Other aspects of the analysis such as the sources of data, the price year, and the use of discounting were reported. In general, the economic analysis was carried out in a robust and transparent fashion.
Analysis and results:The synthesis of costs and benefits was appropriately carried out. The issue of uncertainty was satisfactorily addressed by means of probabilistic and deterministic sensitivity analyses. The authors presented the EVPI, which represents a further strength of the analysis. The results of both the base-case and the sensitivity analyses were clearly reported. The authors acknowledged some limitations to their analysis such as the very small difference in utility valuations.
Concluding remarks:On the whole, the study was well conducted and addressed many areas of uncertainty. The authors’ conclusions are likely to be valid. Funding Funded by the NIHR Health Technology Assessment programme. Bibliographic details Castelnuovo E, Cross P, Mt-Isa S, Spencer A, Underwood M. Cost-effectiveness of advising the use of topical or oral ibuprofen for knee pain: the TOIB study [ISRCTN: 79353052] Rheumatology 2008; 47(7): 1077-1081 Other publications of related interest Underwood M, Ashby D, Cross P, et al. on behalf of the TOIB study team. Advice to use topical or oral ibuprofen for chronic knee pain in older people: randomised controlled trial and patient preference study. Br Med J 2008;336:138-42.
McKell D, Stewart A. A cost-minimisation analysis comparing topical versus systemic NSAIDs in the treatment of mild osteoarthritis of the superficial joints. Br J Med Econ 1994;7:137-47.
Underwood M, Ashby D, Carnes D, et al. Topical or oral ibuprofen for chronic knee pain in older people: the TOIB study. Health Technol Assess. 2008 May;12(22):1 Indexing Status Subject indexing assigned by NLM MeSH Administration, Oral; Administration, Topical; Aged; Analgesics, Non-Narcotic /administration & Anti-Inflammatory Agents, Non-Steroidal /administration & Arthralgia /economics /etiology /prevention & Cost of Illness; Cost-Benefit Analysis; Drug Costs /statistics & Female; Great Britain; Health Care Costs /statistics & Health Resources /utilization; Humans; Ibuprofen /administration & Male; Middle Aged; Osteoarthritis, Knee /complications /drug therapy /economics; Patient Satisfaction; Quality-Adjusted Life Years; State Medicine /economics; control; dosage /adverse effects; dosage /adverse effects; dosage /adverse effects /therapeutic use; numerical data; numerical data AccessionNumber 22008101068 Date bibliographic record published 03/02/2009 Date abstract record published 31/03/2009 |
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