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Within-trial cost-effectiveness of lifestyle intervention or metformin for the primary prevention of type 2 diabetes |
The Diabetes Prevention Program Research Group |
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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 Two interventions, to prevent patients with impaired glucose tolerance from becoming Type II diabetes sufferers, were compared against a placebo. The first intervention was lifestyle changes for the patient, which comprised diet and exercise, aimed at reducing the body weight by 7%. This was reinforced by monthly individual and group sessions. The second intervention was 850 mg of metformin administered orally once per day, increasing to 850mg twice daily after one month.
Study population The study population comprised patients with impaired glucose tolerance, who were older than 25 years and who had a body mass index of greater than 24 kg/m2. The trial used 3,234 patients (68% women), with an average age of 51 years.
Setting The setting was the community. The economic study was undertaken in the USA.
Dates to which data relate The date when the study was initiated was not stated, although it was noted that the closing date for the study data was 31 July 2001 and that the study period was 3 years. The price year was 2000.
Source of effectiveness data The effectiveness data were derived from a single study.
Link between effectiveness and cost data The cost data were taken from the same sample of patients as the effectiveness data.
Study sample The study sample was made up of 3,234 patients (68% women and 45% from minority groups), with an average age of 51 years. All the patients had impaired glucose tolerance. This suggested that the study sample was reflective of those who would potentially benefit from the treatments. The study did not report how many patients were in each of the treatment groups. Power calculations were not used to determine the sample size.
Study design The patients were randomised into each treatment group, although the methods of randomisation were not reported in this study. Details were provided in another paper by the same authors (see Other Publications of Related Interest). The patients were followed up for 3 years. No data on losses to follow-up were provided, although deaths were included in the analysis.
Analysis of effectiveness No data were reported for the methods used in terms of losses to follow up, although deaths were included in the analysis. The groups were not compared at baseline, although this could have been reported in the other paper (see Other Publications of Related Interest). The effectiveness data were reported as health utilities (i.e. quality-adjusted life-years, QALYs), measured using the Self-Administered Quality of Well-Being (QWB-SA) Index. The ratings for each patient were measured annually.
Effectiveness results The patients in the lifestyle and metformin groups exhibited fewer symptoms and better functioning than those in the placebo group. During the 3 years, there were three deaths in the lifestyle group, six in the metformin group, and five in the placebo group (no statistical analysis available).
The quality of life varied according to the treatment group. During the 3 years, the metformin group gained an average of 0.022 QALYs more than the placebo group. In turn, the lifestyle group gained an average of 0.050 QALYs more than the metformin group. It was not stated whether these utilities included those patients who had died during follow-up.
Clinical conclusions The authors concluded that the lifestyle group exhibited better outcomes than the metformin group, which in turn showed better outcomes than the placebo group. Therefore, it was suggested that lifestyle interventions are the most effective method for delaying or preventing Type II diabetes.
Measure of benefits used in the economic analysis The main measure of benefit in the study was the QALYs. QALYs were measured using the QWB-SA Index. The patients completed the assessment on an annual basis.
Direct costs The methods for estimating the costs in this study were reported in detail elsewhere (see Other Publications of Related Interest). The direct costs were for:
identifying individuals with impaired glucose tolerance;
implementing and maintaining the interventions;
side effects;
other medical care, including hospital, emergency room, urgent care and outpatient services;
telephone calls to health care providers; and
prescribing medications.
Other, non-medical direct costs were for exercise classes, exercise equipment, food, food preparation items, and transportation.
The quantities and the costs were not reported separately. The costs were reflated to the present at a rate of 3% per annum. The initial results were discounted, although a 3% discount rate was used in the sensitivity analysis. The price year was 2000.
Statistical analysis of costs No statistical analysis of the costs was performed.
Indirect Costs As already stated, the methods for estimating the costs in this study were reported elsewhere. The indirect costs included the time spent by patients travelling to and from appointments, the time spent exercising, shopping and cooking, and the costs arising from being absent from work or other unusual activity. The resource quantities and the unit costs were not reported separately. The costs were reflated to the present at a rate of 3% per annum. The initial results were discounted, although a 3% discount rate was used in the sensitivity analysis. The price year was 2000.
Sensitivity analysis A one-way sensitivity analysis was undertaken on various parameters. The parameters investigated included personnel costs, intervention effectiveness and discount rates. The ranges were selected arbitrarily and were presented in the form "10% reduction".
Estimated benefits used in the economic analysis During the 3 years, the metformin group gained an average of 0.022 QALYs per patient more than the placebo group. In turn, the lifestyle group gained an average of 0.050 QALYs more than the metformin group. The benefits included all aspects of the individuals' health-related quality of life.
Cost results Over the 3 years, the total health care cost per patient for the lifestyle group was $78 more than the metformin group, while the metformin group cost an average of $2,191 more than the placebo group.
When all the costs were considered (i.e. the societal perspective), the lifestyle group cost $1,128 more than the metformin group, which, in turn, cost $2,412 more than the placebo group.
Synthesis of costs and benefits The results were presented as both the cost per QALY gained and the cost per diabetes case prevented. In the main analysis, from the health care perspective, the lifestyle intervention cost $31,512 per QALY gained when compared with the placebo option. The metformin intervention cost $99,611 per QALY compared with placebo.
From a societal perspective, the lifestyle group cost $51,582 per QALY compared with placebo, whilst the metformin intervention cost $99,171 compared with placebo.
The cost per case prevented from a health care perspective was $15,655 for lifestyle versus placebo, and $31,338 for metformin versus placebo. The corresponding costs from the perspective of society as a whole were $24,426 for lifestyle versus placebo, and $34,489 for metformin versus placebo.
No data were provided showing the incremental cost-effectiveness of the lifestyle intervention compared with metformin.
The sensitivity analysis showed that the findings for the lifestyle intervention were most sensitive to the format of the intervention. If the sessions were implemented in a group of 10 people, then the cost per QALY gained (compared with placebo) would fall to $8,982 from a health care perspective, and $29,052 from a societal perspective.
Authors' conclusions Compared with placebo, both the lifestyle and metformin interventions were cost-effective in reducing the risk of diabetes progression. It was noted that the lifestyle intervention tended to show better outcomes in patients than the metformin treatment, although it also cost slightly more.
CRD COMMENTARY - Selection of comparators A lifestyle intervention and a medical (metformin) intervention were both compared against a common alternative (placebo). Whilst these are reasonable interventions to include, as both are commonly used to prevent the onset of Type II diabetes, it is unfortunate that the incremental cost-effectiveness results were not provided from these two interventions head-to-head.
Validity of estimate of measure of effectiveness The effectiveness data were reported as health utilities (i.e. QALYs). See the 'Validity of Estimate of Measure of Benefit' section.
Validity of estimate of measure of benefit The QALY was used as the summary measure of benefit in this study. This is an established measure of benefit, accounting for both quantity and quality of life. It was noted that the QALY estimates were obtained from patients annually. However, because quality of life varies significantly over time, it may have been useful for utility estimates to have been elicited at more regular intervals.
Validity of estimate of costs A more detailed description of the costing methods was provided in another paper by the same authors (see Other Publications of Related Interest). Consequently, the methods were not detailed in full in this study. It was therefore difficult to draw any firm conclusions about their reliability. The unit costs were not presented, meaning that the results may not be transferable to other settings. However, the costs that were included in the study appear to have been reasonable, and did not exclude any major factors. The costs results were reported separately, from both a health care and societal perspective.
Other issues The authors presented the incremental cost-effectiveness of the lifestyle intervention against placebo, and the incremental cost-effectiveness of the metformin intervention against placebo. However, it would be useful for the lifestyle intervention to be compared directly against the metformin intervention. Whilst the authors noted that both interventions appeared to be cost-effective, it is important that decision-makers establish whether or not one of these options is more cost-effective than the other.
The sample used in the study appears to have been reasonably representative of the population that would use either of the interventions. However, it cannot be assumed that the results would be applicable to all settings. You should consider the generalisability of these findings to your own setting.
In the sensitivity analysis, the authors suggested that by implementing the lifestyle therapy in a group session, the costs would be significantly reduced, thereby improving the cost-effectiveness. However, it may be the case that group therapy is less effective than individual therapy, and this factor should also be considered. Users of this database should be cautious when using this finding in relation to their own settings.
The study period was 3 years. However, Type II diabetes is a disease that remains with patients for their entire life and many long-term factors were not included in this study. It was suggested that future studies of this nature attempt to estimate the lifetime costs and consequences of the interventions under examination.
Implications of the study The authors suggested that both lifestyle and metformin interventions can be considered cost-effective for the prevention of Type II diabetes in patients with impaired glucose tolerance. However, it was suggested that future research should aim to measure the true lifetime costs and benefits associated with these interventions.
Source of funding Supported by the National Institutes of Health through the National Institutes of Diabetes and Digestive and Kidney Diseases, the National Institute of Child Health and Human Development, and the National Institute on Aging; the National Center on Minority Health and Health Disparities, National Center for Research Resources General Clinical Research Center Program, the Office of Research on Women's Health, the Indian Health Service; the Centers for Disease Control and Prevention; the American Diabetes Association; Bristol Myers Squibb; and Parke-Davis
Bibliographic details The Diabetes Prevention Program Research Group. Within-trial cost-effectiveness of lifestyle intervention or metformin for the primary prevention of type 2 diabetes. Diabetes Care 2003; 26(9): 2518-2523 Other publications of related interest The Diabetes Prevention Program Research Group. Costs associated with the primary prevention of type 2 diabetes mellitus in the Diabetes Prevention Program. Diabetes Care 2003;26:36-47.
Indexing Status Subject indexing assigned by NLM MeSH Adult; Attitude to Health; Cost-Benefit Analysis; Diabetes Mellitus, Type 2 /economics /prevention & Female; Humans; Hypoglycemic Agents /economics /therapeutic use; Life Style; Male; Metformin /economics /therapeutic use; Middle Aged; Placebos; Quality of Life; United States; control /psychology AccessionNumber 22003009843 Date bibliographic record published 30/11/2004 Date abstract record published 30/11/2004 |
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