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Cost utility analysis of maintenance treatment for recurrent depression |
Kamlet M S, Paul N, Greenhouse J, Kupfer D, Frank E, Wade 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. Health technology Maintenance treatments for recurrent depression, including interpersonal therapy, imipramine therapy (drug), and a combination of the two.
Study population Patients with recurrent depression.
Setting Hospital and community. The economic study was performed in Pittsburgh, USA.
Dates to which data relate Effectiveness and resource use data were obtained from a randomised controlled trial published in 1990. The utility values for quality of life while depressed and the probability of suicide per depressive episode were estimated based on the values published in the literature between 1978 and 1989. The fiscal year was 1991.
Source of effectiveness data Effectiveness data were derived from a single study, a literature review, and assumptions made by the authors.
Link between effectiveness and cost data Costing was retrospectively performed on the same patient sample as that used in the effectiveness analysis.
Study sample Power calculations were not reported as having been used to determine the sample size. The study had two phases: initial stabilization phase (lasted for about 36 weeks) and the experimental phase of the study consisting of the maintenance therapy. A total of 230 patients (age range 21 to 65 years) were enrolled in the study, of whom 128 patients completed the first phase of the study and started the maintenance therapy. The 128 patients who entered the second phase of the study were randomly allocated to receive maintenance IPT (IPT-M) alone (n=26), IPT-M with imipramine drug therapy (n=25), IPT-M with a placebo drug (n=26), imipramine drug therapy alone (n=28), and placebo alone (n=23).
Study design Randomised controlled clinical trial, conducted in a single centre. The duration of the follow-up was 3 years or until recurrence. The loss to follow-up in the main phase of the study (the maintenance therapy) was 17% (22 patients failing to complete the 3-year protocol mostly due to non-compliance).
Analysis of effectiveness The principle used in the analysis of effectiveness was intention to treat. The primary health outcome used in the analysis was the time until the first recurrence of depression after randomisation to maintenance therapy. A parametric "mixture" model was used to estimate (by the maximum likelihood method) the proportion of patients with a zero probability of recurrence (surviving fraction) and the average time until recurrence for patients not belonging to the surviving fraction.
Effectiveness results The proportion of recurrence-free patients over the entire 3-year experiment for Drug and the IPT-M & Drug maintenance treatments was about 77%. The corresponding figure for the IPT-M & placebo and the IPT-M maintenance treatments was about 28%. The placebo group had a rate of 10% recurrence-free patients over 3 years. The difference between IPT-M & Drug and Drug groups, and the IPT-M & placebo and IPT-M groups was statistically significant (p=0.0026, p=0.0059, and p=0.0144, respectively). The IPT-M & placebo and IPT-M groups had better results than the placebo group (p=0.1038, and p=0.0444). The value of surviving fraction was estimated to be 0.3214 (IPT-M), 0.7547 (Drug), 0.1023 (placebo), 0.6746 (IPT-M & Drug), and 0.2331 (IPT-M & placebo). The corresponding values for the average time until recurrence for patients not belonging to the surviving fraction were 1 over 0.0223, 0.0605, 0.0333, 0.0135, and 0.198, respectively.
Clinical conclusions The authors "see that more patients on the Drug maintenance treatment tend to fall in the surviving fraction, but that those who do have a recurrence in this group do so relatively quickly. On the other hand, a slightly lower proportion of patients in the IPT-M & Drug maintenance treatment group fall in the surviving fraction, but for those who have a recurrence of depression, their expected time until recurrence is much longer than for those patients in the Drug alone group."
Modelling A Markovian state-transition model and Monte Carlo simulation were employed to estimate the expected costs and benefits associated with each maintenance therapy.
Outcomes assessed in the review The utility values for quality of life while depressed and probability of suicide per depressive episode were estimated based on the values published in the literature.
Study designs and other criteria for inclusion in the review 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 A total of 5 studies were included.
Methods of combining primary studies Investigation of differences between primary studies The techniques and methods used in the valuation of health states were reported to be different across the studies included in the review, ranging from the "time trade-off" method, to Quality of Well-being (QWB) Scale. No more information was given.
Results of the review A value of 0.45 (0.3 and 0.7) was chosen for the baseline utility value (range included reasonably pessimistic and optimistic values) for quality of life while depressed. The probability of suicide per depressive episode was estimated to be 0.0025 (0.001 and 0.01). TABLE C
Methods used to derive estimates of effectiveness Estimates of effectiveness were also based on the authors' assumptions.
Estimates of effectiveness and key assumptions Quality of life while stable and under placebo, IPT-M, and IPT-M & placebo was assumed to be 1, whilst for Drug and IPT-M & Drug varying values were attributed (0.7, 0.8, 0.9, and 1). The duration of depressive episode was assumed to be 0.4 (0.2 to 0.6) years.
Measure of benefits used in the economic analysis The main measure of benefit was quality-adjusted life-years (QALYs). The number of depressive episodes averted was used as a measure of benefit when the indirect cost due to lost wages was incorporated in the cost component of the cost-effectiveness ratio. The preferences of the general public were considered in the valuation of the health states using different methods including the "time trade-off" method, and the Quality of Well-being (QWB) Scale.
Direct costs Costs were discounted. Quantities were partially reported separately from the costs. The cost components were reported separately. Direct health services costs were considered: medication and lab work, professional service, and office space. The perspective adopted in the analysis of direct costs was that of a health care system. The sources of cost data were the study institution and the literature. The fiscal years for some of the cost data were 1980 and 1986. The date to which the price data referred was 1991.
Indirect Costs Costs were discounted. Quantities were not reported separately from the costs. The opportunity cost per visit (for IPT-M) of patient's time was estimated. The indirect cost per depressive episode was estimated based on decreased wages per depressive episode. The perspective adopted in the cost analysis was that of a patient. The cost data were extracted from a study published in 1987, and were based on 1980 dollars, which were updated to 1990.
Sensitivity analysis One-way sensitivity analysis was performed on the discount rate. Multi-way sensitivity analyses were carried out based on optimistic and pessimistic scenarios for the length of a depressive episode, quality of life when depressed, cost of a depressive episode and probability that a person commits suicide when depressed. Monte Carlo analysis was performed on the proportion of patients with a zero probability of recurrence.
Estimated benefits used in the economic analysis With zero discount rate and baseline values for the parameters of the model, the QALYs were estimated to be 9.56 for placebo, 15.18 for IPT-M, 14.00 for IPT-M & placebo, and between 14.98 and 21.39 for Drug therapy, depending on the side effects of the treatment, with 22.29 for Drug & IPT-M. A 5% discount rate was considered in the sensitivity analysis. The number of depressive episodes averted for IPT-M and IPT-M & placebo relative to placebo was 13. The corresponding figures for protocols involving Drug were not reported.
Cost results With zero discount rate and baseline values for the parameters of the model, IPT-M had an increase in life time expected costs from $21,204 for the placebo to $34,316. Direct costs associated with drug maintenance treatment were $19,573. Drug & IPT-M led to a direct cost of $48,390. A 5% discount rate was considered in the sensitivity analysis.
Synthesis of costs and benefits Compared with the placebo, the drug treatment was the dominant strategy (cost saving associated with improved health). The cost per QALY for IPT-M and IPT-M & placebo relative to placebo was $2,333, and $2,922, respectively. Overall, the maintenance treatments cost under $5000/QALY for the cost of the resulting health improvements relative to the placebo option. The sensitivity analyses established the robustness of the results to changes in the baseline values of the model.
Authors' conclusions For the patients who met the eligibility standards for the study, drug maintenance treatment is cost-effective in the strongest sense of the term, compared to either a placebo group or IPT-M. It both improves expected lifetime health (measured in QALYs) and reduces direct medical costs, even when relatively severe side effects of the drug are considered.
CRD COMMENTARY - Selection of comparators The reason for the choice of the comparator is clear.
Validity of estimate of measure of benefit Despite a relatively small sample size, the estimates of benefit are likely to be internally valid given the use of a randomised design.
Validity of estimate of costs Quantities were not systematically reported separately from the cost. However, adequate details of methods of cost estimation were given. The study lacked a prospective cost analysis.
Other issues The authors pointed out that the results may not be generalised beyond the category of patient included in the study.
Source of funding Supported in part by National Institute of Mental Health grants MH29618-10 and MH-30915-14.
Bibliographic details Kamlet M S, Paul N, Greenhouse J, Kupfer D, Frank E, Wade M. Cost utility analysis of maintenance treatment for recurrent depression. Controlled Clinical Trials 1995; 16: 17-40 Indexing Status Subject indexing assigned by NLM MeSH Adult; Aged; Combined Modality Therapy; Cost-Benefit Analysis; Costs and Cost Analysis; Depression /drug therapy /economics /therapy; Health; Humans; Imipramine /adverse effects /economics /therapeutic use; Likelihood Functions; Middle Aged; Monte Carlo Method; Placebos; Psychotherapy /economics; Quality of Life; Recurrence; Treatment Outcome; Value of Life AccessionNumber 21995005025 Date bibliographic record published 29/02/2000 Date abstract record published 29/02/2000 |
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