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Cost-utility of three approaches to the diagnosis of sleep apnea: polysomnography, home testing, empirical therapy |
Chervin R D, Murman D L, Malow B A, Totten V |
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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 Diagnosis of obstructive sleep apnea syndrome (OSAS) using overnight polysomnography in a sleep laboratory, home study, or bedside diagnosis of OSAS without any testing.
Study population Hypothetical cohort of persons suspected of having OSAS.
Setting The setting was hospital and community. The study was set in the USA.
Dates to which data relate Effectiveness and resource use data were collected from studies published between 1988 and 1997. Cost data were based on charge data collected from the University of Michigan Sleep Center and on data from a study published in 1996. The price year was not reported.
Source of effectiveness data Effectiveness data were derived from a literature review.
Modelling A decision tree was used to determine the cost-effectiveness of the three approaches to the diagnosis of OSAS. The time horizon was 5 years after evaluation for OSAS.
Outcomes assessed in the review The review assessed utilities, survival, test characteristics, and predictive values.
Study designs and other criteria for inclusion in the review Values for utilities and probabilities were taken from consecutive, sleep-centre-referred, adult case series.
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 Summary statistics from individual studies were extracted. No further details were given in the paper.
Number of primary studies included At least 10 primary studies were included.
Methods of combining primary studies The method of combination of primary studies was not reported.
Investigation of differences between primary studies Results of the review Utility and mean survival during a 5-year period were:
0.87 and 5 years for a health state of OSAS and continuous positive airway pressure (CPAP),
0.63 and 5 years for a health state of no OSAS and CPAP,
0.63 and 4.7 for a health state of OSAS and no CPAP,
0.75 and 5 for a health state of no OSAS and no CPAP.
EdenTrace Model 2700 for polysomnography had a sensitivity of 0.95, a specificity of 0.96, a positive predictive value of 0.99, and a negative predictive value of 0.77. The proportion of all home studies expected to yield positive results was 0.81.
Methods used to derive estimates of effectiveness Estimates of effectiveness were also based on the authors' assumptions.
Estimates of effectiveness and key assumptions The authors assumed that polysomnography had a sensitivity of 1.0 and a specificity of 1.0.
Measure of benefits used in the economic analysis Quality-adjusted life years (QALYs) for the first 5 years after evaluation for OSAS were used as the measure of benefits. 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 reported separately. Direct costs related to direct diagnostic and treatment costs and included costs of tests, office visits, and CPAP setups. The quantity/cost boundary adopted was that of the health service. The estimation of quantities and costs was based on actual data. Charges were obtained from the University of Michigan Sleep Centre. The price year was not reported.
Indirect Costs Indirect costs were discounted at an annual rate of 3%. Quantities and costs were reported separately. Indirect costs related to costs of long-term health services required when OSAS remained untreated. No further details were given. The quantity/cost boundary adopted was that of society. The estimation of quantities and costs was based on actual data. Costs and quantities were collected from a study published in 1996. The price year was not reported.
Sensitivity analysis Univariate and two-variate sensitivity analyses were conducted on utilities, survival rates, pretest probabilities of OSAS, test characteristics, and costs. A 1,000-iteration Monte Carlo simulation was also performed.
Estimated benefits used in the economic analysis 4.019 QALYs were generated for polysomnography, 3.955 for home study, and 3.934 for no testing.
Cost results Charges for a patient with OSAS were $4,210 for polysomnography, $3,460 for home study, and $3,020 for no testing. Charges for a baseline patient (with or without OSAS) were $3,799 for polysomnography, $2,939 for home study, and $3,020 for no testing.
Synthesis of costs and benefits The incremental cost-utility ratio of polysomnography over home study was $13,431 per QALY gained. The incremental cost-utility ratio of polysomnography over no testing was $9,165 per QALY gained. When the utility of CPAP in patients without OSAS was at least 0.75, the no testing option dominated polysomnography.
Authors' conclusions The cost-utility of polysomnography instead of home study or no testing, in the diagnosis of OSAS compares favourably with that of other procedures for which society judges the added utility per dollar spent to be worthwhile.
CRD COMMENTARY - Selection of comparators A justification was given for the comparators used, namely that they were currently available diagnostic strategies. You, as a user of this database, should decide if these health technologies are relevant to your setting.
Validity of estimate of measure of benefit The authors did not state that a systematic review of the literature had been undertaken. More information about the design of the review and the method of combining primary effectiveness estimates could have been reported. The estimation of benefits was modelled. The standard gamble instrument used to derive a measure of health benefit was appropriate. Effectiveness estimates were derived from a study involving only 19 patients who complied with therapy. The discount rate for benefits was 3%, but different rates might apply outside the USA.
Validity of estimate of costs Some good features of the cost analysis were that all relevant cost categories were included, sensitivity analyses were conducted on costs and quantities, and quantities and costs were reported separately. However, the price year was not reported and charges were used to proxy prices, which is a limitation when applying the study findings in other settings or countries. In addition, the discount rate applied to costs was 3%, and this might differ from the rates used in other countries.
Other issues The authors did not make appropriate comparisons of their findings with those from other studies. The uncertainties in the data were addressed by means of a set of sensitivity analyses. However, only some of the variables were considered, while others (for example, the discount rate) appear not to have been considered. This limits the generalisability of the results. The authors did not present their results selectively. The study considered patients suspected of having OSAS and this was reflected in the authors' conclusions. A longer perspective would most likely increase the cost-effectiveness of polysomnography. As the authors acknowledged, they only examined three options in the diagnosis of OSAS and one type of home study, although several others exist. This study is based on the premise that all patients being evaluated for OSAS should undergo the same diagnostic test regardless of the pretest probability of the disorder. Future studies should be conducted to challenge this premise.
Implications of the study More precise determination of certain key variables in this model should be a goal of future research.
Bibliographic details Chervin R D, Murman D L, Malow B A, Totten V. Cost-utility of three approaches to the diagnosis of sleep apnea: polysomnography, home testing, empirical therapy. Annals of Internal Medicine 1999; 130(6): 496-505 Other publications of related interest Comment in: Annals of Internal Medicine 1999;130(6):533-4.
Indexing Status Subject indexing assigned by NLM MeSH Cost-Benefit Analysis; Decision Trees; Humans; Monitoring, Physiologic /economics; Polysomnography /economics; Positive-Pressure Respiration; Quality-Adjusted Life Years; Sensitivity and Specificity; Sleep Apnea Syndromes /diagnosis /physiopathology /therapy AccessionNumber 21999008104 Date bibliographic record published 31/05/2001 Date abstract record published 31/05/2001 |
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