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Cost-effectiveness of the primary prevention of non-insulin dependent diabetes mellitus |
Segal L, Dalton A C, Richardson J |
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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 Programmes for the primary prevention of non-insulin dependent diabetes mellitus (NIDDM).
Economic study type Cost-effectiveness analysis.
Study population The study targeted selected groups including persons with IGT, overweightese men, seriously obese persons, women with previous gestational diabetes and the general population.
Setting Hospital, community, and primary care. The economic study was carried out in Australia.
Dates to which data relate The effectiveness data were derived from studies published from 1985 to 1997. The resource use data were mainly extracted from reports published in 1994 and 1995. The price year was 1997.
Source of effectiveness data The clinical probabilities were mainly derived from a wide range of studies published between 1985 to 1997. Some of the transition probabilities were extracted based on the opinion of the research team and their clinical advisors. The final health outcomes were derived from a Markov model.
Modelling A Markov model was constructed to estimate the cost-effectiveness of the programmes using transition probabilities, resource utilisation and cost data.
Outcomes assessed in the review Transition probabilities between states (NIDDM, IGT, NGT) for overweight men from state at time t to state at time t+5, annual mortality for men adjusted for metabolic state, and annual mortality for men adjusted for over-weight were the outcomes assessed in the review and reported in the paper.
Study designs and other criteria for inclusion in the review The authors favoured primary studies with randomised design, at least five years of follow-up, and recorded impact on weight and diabetes status, but, as only a small number of studies fulfilled those criteria, the authors also included non-randomised and observational studies and studies with <5 years of follow-up.
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 Twenty one primary studies were included in the review.
Methods of combining primary studies Investigation of differences between primary studies Results of the review Transition probabilities between states (NIDDM, IGT, NGT) for overweight men from state at time t to state at time t+5 for successful intervention group, which were derived from the literature had a range from 0.106 (for the probability of transition from IGT state at time t to NIDDM state at time t+5) to 0.522 (for the probability of transition from IGT state at time t to NGT state at time t+5). The corresponding values for the control group and unsuccessful intervention group had a range from 0.07 (for the probability of transition from NGT state at time t to IGT state at time t+5) to 0.428 (for the probability of transition from IGT state at time t to IGT state at time t+5). Annual mortality adjusted for metabolic state for successful intervention cohort (men) ranged from 0.28 (deaths/100) for the age category 45-49 with NGT to 4.64 for the age category 65-69 with NIDDM. The corresponding values for the control group and unsuccessful intervention group had a range from 0.33 (deaths/100) for the age category 45-49 with NGT to 5.57 for the age category 65-69 with NIDDM.
Methods used to derive estimates of effectiveness The opinions of the research teams and their clinical advisors were used to derive some of the transition probabilities.
Estimates of effectiveness and key assumptions Transition probabilities between states (NIDDM, IGT, NGT) for overweight men from state at time t to state at time t+5 for successful intervention group, which were derived from expert opinion, had a range from 0.01 (for the probability of transition from NGT state at time t to NIDDM state at time t+5) to 0.95 (for the probability of transition from NGT state at time t to NGT state at time t+5). The corresponding values for the control group and unsuccessful intervention group had a range from 0.01 (for the probability of transition from NGT state at time t to NIDDM state at time t+5) to 0.95 (for the probability of transition from NGT state at time t to NIDDM state at time t+5). The key conservative assumption was that "the outcomes of the unsuccessful intervention group would be identical to the control cohort".
Measure of benefits used in the economic analysis The main benefit measures were life years gained and reduction in diabetes years, estimated for each of six programmes included in the study, and also for a general and all-IGT targetpopulation using a Markov model.
Direct costs Costs were discounted. Quantities were not reported separately from costs. Cost items were not reported separately. Some of the cost items mentioned in the paper were inpatient costs, medical costs, and the cost of the commercial programme. A comprehensive list of all cost item included in all programme costs was not given. The average programme costs were reported. The sources of cost data were different Australian institutions. The date to which the price data referred was 1997. The cost analysis was performed from the perspective of the health care service.
Currency Australian dollars (Aus$). A conversion to US dollars was made using a median exchange rate for Aug/Sept/Oct 1997 of Aus$1 = US$0.72.
Sensitivity analysis A set of one-way sensitivity analyses was performed on all key parameters of the model to assess the possible effects on the cost-effectiveness results.
Estimated benefits used in the economic analysis The range of net life years gained due to interventions ranged from 43 for GP advice to 423 life years per 100 persons for surgery for seriously obese. The range of reduction in diabetes years was from 10 for GP advice to 927 diabetes years per 100 participants for surgery for seriously obese. The duration of the benefits was assumed to be life time. Benefits were discounted at 5% discount rate.
Cost results The discount rate was 5%. Total costs of programmes were not reported.
Synthesis of costs and benefits Costs and benefits were combined by calculating the (marginal, assumed equal to average cost) cost per life year saved. Type I for IGT only, type IV for all groups of participants and type V programmes hadnet savings (the values were not given). The remainder of the programmes had a range of cost-effectiveness ratios from Aus$1,000 for type VI to Aus$12,300 for type III.
Authors' conclusions The authors concluded that this "research suggests that there are alternatives - that NIDDM is a disease for which prevention options exist and that interventions may be cost-saving or highly cost-effective relative to other possible uses of health care resources".
CRD COMMENTARY - Selection of comparators The reason for the choice of the comparator(s) is clear.
Validity of estimate of measure of benefit Since the estimation of the benefit outcomes was not solely based on primary studies with randomised design, the internal validity of benefit estimates is not assured.
Validity of estimate of costs Resource utilisation was not reported separately from the costs. The cost items involved in the estimation of average programme costs were not reported separately. Indirect costs were not included in the cost analysis.
Other issues The issue of generalisability to other settings or countries was not properly addressed. As there is no evidence of a systematic search of the literature, the extent to which all relevant studies were included is not clear.
Implications of the study Conducting a study incorporating quality of life impacts and indirect costs is highly desirable.
Source of funding Financial support from the Department of Human Services, Victoria. Core funding for the Centre for Health Program Evaluation from the National Health and Medical Research Council, Monash University and the Victorian Health Promotion Foundation.
Bibliographic details Segal L, Dalton A C, Richardson J. Cost-effectiveness of the primary prevention of non-insulin dependent diabetes mellitus. Health Promotion International 1998; 13(3): 197-209 Indexing Status Subject indexing assigned by CRD MeSH Behavior Therapy; Cost-Benefit Analysis; Diabetes Mellitus, Type 2 /prevention & Diabetes, Gestational; Glucose; Glucose Intolerance; Health Promotion /economics; Life Style; Obesity; Risk Factors; control AccessionNumber 21998008226 Date bibliographic record published 31/03/1999 Date abstract record published 31/03/1999 |
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