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Cost-effectiveness model of adjunctive lamotrigine for the treatment of epilepsy |
Markowitz M A, Mauskopf J A, Halpern M T |
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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. Health technology Anti-epileptic drugs (AEDs) for patients with refractory epilepsy.
Economic study type Cost-effectiveness analysis
Study population Patients over the age of 16 with refractory epilepsy.
Setting Hospital. The economic analysis was conducted in Research Triangle Park, North Carolina, USA.
Dates to which data relate Data on effectiveness and resource use were collected from literature published between 1992 and 1998. The price years used were not stated.
Source of effectiveness data Effectiveness data were derived from a review or synthesis of previously published studies
Modelling A decision analysis model was used to combine information on clinical effectiveness and cost/resource use data identified from published literature. The model considered the impact of adjunctive lamotrigine therapy on costs and health outcomes for patients over a 10 year period, estimating cost-effectiveness of lamotrigine for patients in different stages of refractory epilepsy at the end of year 1, year 2 and years 3 - 10. It was assumed that patients would discontinue use of lamotrigine at the end of the first year if the improvement in seizure free days had been less than 25%.
Outcomes assessed in the review The outcomes assessed were the reduction in frequency of seizures and seizure free days from additional use of lamotrigine.
Study designs and other criteria for inclusion in the review Clinical trials of lamotrigine for patients with epilepsy.
Sources searched to identify primary studies Criteria used to ensure the validity of primary studies Methods used to judge relevance and validity, and for extracting data Number of primary studies included Methods of combining primary studies Investigation of differences between primary studies Results of the review Using adjuvant lamotrigine plus older AEDs the additional seizure free days gained were 10.8 in year 1, 31.2 in year 2 and 25.18 days in years 3-10.
Measure of benefits used in the economic analysis The benefit measure was seizure-free days gained. Benefits were discounted at a rate of 3%.
Direct costs Costs were determined from the perspective of the health care system. Data on the costs of treatment and resource use for intractable seizures were derived from literature published before the availability of the new AEDs. Resource use for patients receiving lamotrigine were taken from published clinical trials. The average wholesale price for lamotrigine, reported in the 1995 Drug Topic Red Book, was used in estimating costs of drug use. Where data were not available, experts were consulted for clinical relevance of cost and resource data. Costs and benefits were discounted at a rate of 3% per annum. The base price year used was not stated.
Sensitivity analysis Sensitivity analyses were conducted varying a number of parameters such as the probability of surgery in the second year, costs of treatment, and hospitalisation rates. The precise types of sensitivity analyses used were not reported.
Estimated benefits used in the economic analysis In the base case scenario, over the 10 year period, 106 seizure free days per patient would be gained.
Cost results The 10 year total costs for the lamotrigine group and the AED group alone were not reported, although the incremental cost of lamotrigine would be $728. Total costs per patient for the two groups respectively in year one would be $3,130 and $2,224 and in year two these costs would be $10,560 and $14,146. The costs of required treatment for patients in years 3 - 10 were $2,172 (lamotrigine) and $1,762 (AED). Adverse events including the need for surgery were included in these cost estimates.
Synthesis of costs and benefits The incremental cost per seizure free day gained was $6.90. The baseline results were sensitive to the results of sensitivity analysis, in particular the estimates of the impact of the intervention on the need for surgery and surgical evaluation and the numbers of seizure free days gained each year. Incremental cost effectiveness per seizure free day gained varied between $-5.61 and $63.60
Authors' conclusions The additional costs of adjuvant lamotrigine therapy for patients with refractory epilepsy are likely to be offset by reduction in the need for other medical procedures, in particular surgery and surgical evaluation.
CRD COMMENTARY - Selection of comparators A justification was provided for the comparators used, as these were older AEDs used for the treatment of refractory epilepsy without adjuvant therapy using a newer AED. Other interventions are available for the treatment of epilepsy, but the authors stated that there was a lack of available clinical data.
Validity of estimate of measure of benefit Estimates of clinical benefit were taken from published controlled clinical trials. However, this estimate may be subject to bias, as the paper does not report on the methods used to identify and pool results from the literature. Furthermore, the paper does not appear to indicate clearly how many clinical trials were used in the analysis.
Validity of estimate of costs Sufficient detail is provided on the source and estimate of costs, although the price years used were not clearly stated. However, as noted by the authors, much of this information could not be found from observational data, and instead, assumptions had to be made by the authors. Sensitivity analysis demonstrated that differences in assumptions on costs and resource use could lead to much variance in cost-effectiveness ratios. The authors noted that indirect costs were not included due to a lack of information. Future analysis should consider these other costs, as the authors themselves estimated that these may represent more than 60% of the total costs of care for epilepsy patients.
Other issues The cost-effectiveness estimates reported by the authors are unlikely to be generalisable to other settings and should be viewed as an indication that more work is required to compare the effectiveness of treatments for epilepsy, and in particular to consider the consequences of treatments in relation to the demand for additional medical resources such as surgical procedures.
Implications of the study Well-designed economic studies and systematic reviews are required to compare interventions for the treatment of epilepsy.
Source of funding Support from Burroughs Wellcome/Glaxo Wellcome.
Bibliographic details Markowitz M A, Mauskopf J A, Halpern M T. Cost-effectiveness model of adjunctive lamotrigine for the treatment of epilepsy. Neurology 1998; 51(4): 1026-1033 Indexing Status Subject indexing assigned by NLM MeSH Ambulatory Care Facilities /economics; Anticonvulsants /administration & Cost of Illness; Cost-Benefit Analysis; Drug Costs; Drug Resistance; Epilepsy /drug therapy /economics /surgery; Health Care Costs /statistics & Hospitalization /economics /statistics & Humans; Outcome Assessment (Health Care) /economics; Triazines /administration & United States; dosage /economics; dosage /economics; numerical data; numerical data AccessionNumber 21998001610 Date bibliographic record published 30/04/2000 Date abstract record published 30/04/2000 |
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