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Efficient patient identification strategies for women with osteoporosis |
Abbott T A, Mucha L, Manfredonia D, Schwartz E N, Berger M L |
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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 Several strategies for the identification of women with osteoporosis were examined. Osteoporosis was defined as a T-score of less than -2.5 when using the bone mineral density (BMD) measurement, as recommended by the World Health Organization. The strategies comprised various combinations of central dual X-ray absorptiometry (DXA), periferal dual X-ray absorptiometry (pDXA) and Simple Calculated Osteoporosis Risk Estimation (SCORE, a pre-screening risk assessment questionnaire), performed at several sites. The 12 screening strategies evaluated in the study were:
DXA hip and spine (strategy 1);
pDXA alone (strategy 2);
DXA hip alone (strategy 3);
DXA spine alone (strategy 4);
pDXA and DXA hip and spine (strategy 5);
SCORE plus pDXA (strategy 6);
SCORE plus hip DXA (strategy 7);
SCORE plus spine DXA (strategy 8);
SCORE plus hip and spine DXA (strategy 9);
SCORE plus pDXA, DXA hip and spine (strategy 10);
SCORE plus pDXA plus test all remaining non osteoporotic women using hip and spine DXA (strategy 11);
SCORE plus pDXA plus test only remaining osteopenic women using hip and spine DXA (strategy 12).
The authors stated that strategy 1 was generally considered to be the "gold" standard.
Economic study type Cost-effectiveness analysis.
Study population The study population comprised postmenopausal women older aged 50 years or older.
Setting The setting of the study was not explicitly stated. The economic study was carried out in northern California, USA.
Dates to which data relate The dates relating to the effectiveness and resource use data were not reported. The price year was not given.
Source of effectiveness data The effectiveness evidence came from a single study.
Link between effectiveness and cost data The costing was performed prospectively on the same sample of patients as that used in the effectiveness study.
Study sample Power calculations do not appear to have been performed. A sample of 392 eligible women who were retirees or active employees participated voluntarily in an osteoporosis education and awareness programme. The mean age was 62 years (standard deviation, SD=8.6). Forty-seven per cent were aged 50 to 59 years, 31% were aged 60 to 69 years, 20% were aged 70 to 79 years, and 2% were aged 80 years or older. The mean weight was 64.4 kg. Of these 392 women, 100 were identified as having osteoporosis with a T-score of less than -2.5 at any one site or more. Measurements at the hip and spine were made using DXA with a Lunar DPX-IQ, while measurements at the forearm were taken using pDXA with a Norland PDEXA.
Study design This was a diagnostic cohort study where all the patients tested by the different diagnostic tests were deemed to be positive for osteoporosis. It was likely to have been carried out in a single centre (a corporation in northern Carolina). All the women completed all of the tests. The order of the tests, and whether it was randomised, was not reported. There was no discussion of who performed the tests. It was implied that all of the tests were performed on the same day.
Analysis of effectiveness All of the patients included in the initial study sample were taken into account when estimating the effectiveness. The primary outcome measure used in the analysis was the sensitivity of each of the 12 screening strategies evaluated in the study.
Effectiveness results According to the BMD results, there were 100 osteoporotic women (T-score less than -2.5).
The sensitivity was 84% for strategy 1, 38% for strategy 2, 41% for strategy 3, 65% for strategy 4, 100% for strategy 5, 38% for strategy 6, 41% for strategy 7, 63% for strategy 8, 82% for strategy 9, 98% for strategy 10, 98% for strategy 11, and 90% for strategy 12.
Clinical conclusions The effectiveness analysis showed that strategy 5 had the greatest sensitivity and detected all osteoporotic women. Strategy 2 detected the lowest number of osteoporotic women.
Measure of benefits used in the economic analysis The benefit measure used in the economic analysis was the number of cases detected with each screening strategy. It corresponded to the sensitivity of the techniques, as estimated in the effectiveness study.
Direct costs Discounting was not relevant because the costs were incurred in a short time period. The economic evaluation considered only the costs of the tests under evaluation in the present study. The unit costs were analysed separately from the quantities of resources used (one test for each woman included in the effectiveness study). The source of the cost data was not stated, but the data were likely to have been derived by the authors from market prices. The dates during which the resource consumption data were collected were not stated. The price year was not reported. The cost/resource boundary adopted in the study was that of the health care provider.
Statistical analysis of costs The costs were treated deterministically.
Indirect Costs The indirect costs were not included in the economic analysis.
Sensitivity analysis A univariate sensitivity analysis was carried out. This varied the cost of the combined test of hip and spine DXA, which in some areas was provided as if it were a single test, rather than two procedures as considered in the base analysis.
Estimated benefits used in the economic analysis See the 'Effectiveness Results' section.
Cost results The total costs were $78,400 with strategy 1, $13,720 with strategy 2, $47,040 with strategies 3 and 4, $92,120 with strategy 5, $12,740 with strategy 6, $38,920 with strategies 7 and 8, $63,560 with strategy 9, $74,340 with strategy 10, $66,740 with strategy 11, and $41,540 with strategy 12.
Synthesis of costs and benefits The costs and benefits of the screening strategies were combined by calculating the average and incremental costs per patient detected.
The cost per patient detected was $200 with strategy 1, $35 with strategy 2, $120 with strategies 3 and 4, $235 with strategy 5, $32 with strategy 6, $99 with strategies 7 and 8, $162 with strategy 9, $190 with strategy 10, $170 with strategy 11, and $106 with strategy 12.
Four strategies (5, 6, 11 and 12) were on the efficiency frontier. After ordering them according to their sensitivity (from lowest to highest: 6, 12, 11 and 5), the incremental cost per patient detected was calculated. This was $335 with strategy 6 over no testing, $554 with strategy 12 over strategy 6, $3,149 with strategy 11 over strategy 12, and $12,690 with strategy 5 over strategy 11.
The result of the sensitivity analysis showed that the ranking of the strategies remained the same, although the absolute values changed.
Authors' conclusions The study identified the four most efficient strategies for detecting osteoporosis among postmenopausal women. However, the authors concluded that the choice of the screening option depends on patient preferences, co-morbidities, the decision-makers willingness to pay and other factors.
CRD COMMENTARY - Selection of comparators It seems that the authors considered all possible options for osteoporosis screening, including the strategy considered to be the "gold" standard and the no screening option. You should decide whether they represent actual screening options in your own setting.
Validity of estimate of measure of effectiveness The effectiveness study used a diagnostic cohort study where all the patients tested by the different diagnostic tests were deemed to be positive for osteoporosis. The women included in the study were volunteers, thus it was unclear whether the study sample was representative of the study population. All of the women underwent every test. However, the order of testing and whether the order was randomised were not reported. It was not discussed whether the test investigators were blind to the results of prior tests. Hence, the degree of bias potentially present in the study is unclear.
Validity of estimate of measure of benefit The summary benefit measure was derived from the effectiveness results.
Validity of estimate of costs The perspective adopted in the study was stated and only the costs of the diagnostic procedures were included in the economic evaluation. The unit costs and the quantities of resources used were analysed separately. However, the price year was not reported, thus making reflation exercises in other settings difficult. The costs were treated deterministically and the cost estimates were specific to the study setting. However, the authors considered an alternative estimate for the cost of one strategy.
Other issues The authors did not compare their findings with those from other studies. In terms of the generalisability of the study results, the authors stated that caution is required when interpreting the conclusions of the study. This is due to potential differences in the characteristics of the study population and in the prevalence rate, which may vary in other settings, as well as the definition of osteoporosis. The authors noted some limitations of the analysis, such as the design of the study.
Implications of the study The study results suggest that four alternative screening options for osteoporosis among postmenopausal women may be cost-effective from the perspective of the health care provider. The choice will depend on the trade-off between extra costs and additional cases of osteoporosis detected. The authors also noted that new technologies may be released and the results of their study should be revisited.
Bibliographic details Abbott T A, Mucha L, Manfredonia D, Schwartz E N, Berger M L. Efficient patient identification strategies for women with osteoporosis. Journal of Clinical Densitometry 1999; 2(3): 223-230 Indexing Status Subject indexing assigned by NLM MeSH Absorptiometry, Photon /economics; Aged; Bone Density; Cost-Benefit Analysis; Costs and Cost Analysis; Female; Femur Neck /radiography; Forearm /radiography; Humans; Lumbar Vertebrae /radiography; Middle Aged; Osteoporosis, Postmenopausal /diagnosis; Risk Factors; Sensitivity and Specificity; Surveys and Questionnaires AccessionNumber 21999001805 Date bibliographic record published 31/01/2004 Date abstract record published 31/01/2004 |
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