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Which unruptured cerebral aneurysms should be treated? A cost-utility analysis |
Johnston S C, Gress D R, Kahn J G |
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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 Treatment of unruptured cerebral aneurysms.
Study population Hypothetical cohort of 50-year-old women.
Setting Hospital. The study was carried out at the hospital of the University of California, San Francisco.
Dates to which data relate Effectiveness data were derived from studies published between 1984 and 1999. Resource use and cost estimates were based on data obtained from the hospital of the University of California from 1994 to 1997 and studies published between 1995 and 1999. The price year was 1997.
Source of effectiveness data Effectiveness data were derived from a literature review.
Modelling Markov models were used to estimate costs and benefits over the projected lifetime of the cohort.
Outcomes assessed in the review The review assessed the following outcomes: aneurysm rupture rates, all-cause mortality rates, case fatality and permanent disability rates for SAH, mortality and permanent complication rates for clipping and coiling.
Study designs and other criteria for inclusion in the review The following hierarchy was followed according to the availability of each type of data: the most recent meta-analysis, prospective and cohort studies, case-control and case-series data, and lastly, estimations based on consultation with experts in the field.
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 Data were extracted from individual studies on the basis of summary statistics.
Number of primary studies included Approximately 15 studies were included.
Methods of combining primary studies Investigation of differences between primary studies Results of the review Aneurysm rupture rates per year were:
0.05%, patients with no history of SAH and aneurysms smaller than 10 mm,
1%, patients with no history of SAH and aneurysms greater than 10 mm,
0.5%, patients with a history of SAH and aneurysms smaller than 10 mm,
1%, patients with a history of SAH and aneurysms greater than 10 mm.
The probabilities of SAH case fatality was 0.45, of SAH case permanent mild disability was 0.14, and of SAH case permanent moderate/severe disability was 0.15.
The relative risk of mortality with mild disability was 1.96 and the relative risk of mortality with moderate/severe disability was 3.73.
With respect to clipping, the probabilities of case fatality, case permanent mild disability and case permanent moderate/severe disability were 2.6%, 5.1%, and 5.8%. The post-treatment yearly rupture rate was 0. With respect to coiling, the probabilities of case fatality were 0.4%, of case permanent mild disability were 2.5% and of case permanent moderate/severe disability were 2.8%. The post-treatment relative risk of rupture was 0.1. These were the principal input parameters used in the model.
Measure of benefits used in the economic analysis Benefits were measured in quality-adjusted life years (QALYs). Median utilities for mild strokes and an average of moderate and major strokes were used to define utilities for mild and moderate/severe disability health states, respectively. Utilities for untreated patients varied with rupture rates. Utilities for pain or compressive symptoms were estimated from valuation of the state with frequent pain relieved by medications described in Health Utilities Index Mark 2. Benefits were discounted at an annual rate of 3%.
Direct costs Direct costs were discounted at an annual rate of 3%. Quantities and costs were not reported separately. Costs included all direct medical costs associated with the clipping and coiling procedures and with SAH (hospital, physician fees, outpatient, rehabilitation, and nursing home/home care). The quantity/cost boundary adopted was that of society. The estimation of quantities and costs was based on actual data. Physician professional fees were derived from the 1997 Medicare fee schedule for San Francisco. For costs after the acute hospitalisation, the authors used published figures for 1991 Medicare costs during the first 6 months after a stroke. Annual direct costs for caring for disabled patients were taken from data on long-term care in stroke patients. Costs were converted to 1997 dollars using the Medical Care category of the Consumer Price Index.
Statistical analysis of costs Sensitivity analysis Univariate sensitivity analysis was performed by varying each input variable throughout its full range while holding other variables constant. Multivariable sensitivity analysis was performed using a Monte Carlo simulation with all input variables and 10,000 trials.
Estimated benefits used in the economic analysis Depending on the clinical scenario, the number of QALYs generated by no treatment varied between 14.8 and 19.1. The number of QALYs generated by coiling varied between 18.4 and 18.6. The number of QALYs generated by clipping was 17.5, irrespective of the clinical scenario.
Cost results Depending on the clinical scenario, total costs associated with no treatment varied between $800 and $14,300. Total costs associated with coiling varied between $29,400 and $30,800. Total costs associated with clipping were $42,700, irrespective of the clinical scenario.
Synthesis of costs and benefits Incremental cost per QALY was determined where relevant. For scenario A, the case of a 50-year-old woman with no symptoms or history of SAH from another aneurysm with an unruptured aneurysm less than 10 mm in diameter, the no treatment option was the most cost-effective. For clipping, all scenarios with aneurysms greater than 10 mm in diameter or with symptoms associated with the aneurysm were cost-effective, with cost-utility ratios ranging from $11,000/QALY to $38,000/QALY.
For coiling, all scenarios other than the base case were cost-effective, with cost-utility ratios of $5,000/QALY to $42,000/QALY, and confidence intervals were less than $100,000/QALY for all symptomatic aneurysms and those larger than 10 mm in patients with no prior history of SAH. Comparing clipping to coiling, there were marginally lower cost-utility ratios for coiling, and net QALYs were 0.9 to 1 greater for coiling in all scenarios. In univariate analysis, the cost-effectiveness depended most sensitively on patient age and SAH rates of untreated aneurysms.
Authors' conclusions Treatment of small, asymptomatic, unruptured cerebral aneurysms in patients without a history of SAH worsens clinical outcomes, and thus is neither effective nor cost-effective. For aneurysms that are larger than 10 mm or symptomatic, or in patients with a history of SAH, treatment appears to be cost-effective.
CRD COMMENTARY - Selection of comparators The rationale for the choice of the comparators was clear. You, as a user of this database, should verify whether these health technologies are relevant to your setting.
Validity of estimate of measure of benefit The effectiveness data used to construct the decision tree have been derived from, what may have been, a non-systematic review of the literature. The internal validity of the data derived from the literature cannot be fully assessed given the limited information provided about the literature review and any quality assessment of the primary studies. For instance, rupture rates have been derived from a single study based on retrospective data. These results may be subject to selection bias if physicians failed to enrol patients who have already died from aneurysm rupture. Complication rates were derived from a single, non-randomised cohort study. Effectiveness estimates derived from primary studies were not combined. Given the absence of studies of the disutility due to SAH or the procedures, utility estimates were based on the disability of brain injury due to strokes.
Validity of estimate of costs Only direct costs were considered. Indirect costs related to lost productivity were not included. The authors' claim that the perspective is 'societal' is therefore not supported by the range of cost analysis. Cost estimates were derived from local sources and other previously published studies. Hence, it is difficult to assess the generalisability of these results to other settings.
Other issues Adequate comparisons with other studies were made. However, the generalisability of the results to other settings or countries was not discussed. The authors do not appear to have presented their results selectively. The study enrolled patients with asymptomatic unruptured cerebral aneurysms and this was reflected in the authors' assumptions. The authors have used the results of recent trials to obtain a more comprehensive picture regarding the most cost-effective approach to treating this condition.
Implications of the study Treatment of small, asymptomatic, unruptured cerebral aneurysms in patients without a history of SAH is not cost-effective. For aneurysms that are larger than 10 mm or symptomatic, or in patients with a history of SAH, treatment appears to be cost-effective.
Source of funding Dr S C Johnston is a Fellow of the National Stroke Association and is supported by grant NIH/NINDS (K08 NS 02042-01).
Bibliographic details Johnston S C, Gress D R, Kahn J G. Which unruptured cerebral aneurysms should be treated? A cost-utility analysis. Neurology 1999; 52(9): 1806-1815 Other publications of related interest 1. Raaymakers T W, Rinkel G J, Limburg M, Algra A. Mortality and morbidity of surgery for unruptured intracranial aneurysms: a meta-analysis. Stroke 1998;29(8):1531-1538.
2. King J T, Glick H A, Mason T J, Flamm E S. Elective surgery for asymptomatic, unruptured, intracranial aneurysms: a cost-effectiveness analysis. Journal of Neurosurgery 1995;83(3):403-412.
3. Kallmes D F, Kallmes M H, Cloft H J, Dion J E. Guglielmi detachable coil embolisation for unruptured aneurysms in non-surgical candidates: a cost-effectiveness exploration. American Journal of Neuroradiology 1998;19(1):167-176.
4. Brown B M, Soldevilla F. MR angiography and surgery for unruptured familial intracranial aneurysms in persons with a family history of cerebral aneurysms. American Journal of Roentgenology 1999;173(1):133-138.
Indexing Status Subject indexing assigned by NLM MeSH Cost-Benefit Analysis; Female; Humans; Intracranial Aneurysm /economics; Male; Middle Aged; Models, Neurological; Quality of Life; Risk Factors AccessionNumber 21999001161 Date bibliographic record published 30/06/2000 Date abstract record published 30/06/2000 |
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