|Evaluation of excessive anticoagulation in a group model health maintenance organization
|Lousberg T R, Witt D M, Beall D G, Carter B L, Malone D C
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.
Using phytonadione and/or fresh frozen plasma (FFP) versus the conservative management option in the management of patients with excessive anticoagulation. The conservative management was defined as temporary discontinuation of warfarin therapy until the international normalized ratio (INR) falls to within therapeutic range.
Economic study type
Patients with episodes of INRs greater than 6.0.
Hospital. The economic study was conducted in the USA.
Dates to which data relate
The effectiveness and resource use data corresponded to patients managed from December 1994 until August 1995. The price year was not clearly reported.
Source of effectiveness data
Effectiveness data were derived from a single study.
Link between effectiveness and cost data
The costing was undertaken prospectively on the same patient sample as that used in the effectiveness analysis.
No power calculations were reported. A total of 301 episodes of excessive anticoagulation, corresponding to 248 patients from a total of 262 candidates, was included in the analysis. The conservative management group included 249 episodes, whereas the intervention group (phytonadione and/or FFP) group consisted of 52 episodes.
This was a retrospective cohort study conducted in a single group model HMO. The duration of follow-up was not clearly reported.
Analysis of effectiveness
The analysis was based on treatment completers (those with complete or available data). The primary health outcome used in the analysis were the percentage of managed episodes with no sequelae and incidence of major bleeding after initiation of therapy.
The percentage of managed episodes with no sequelae was 85.1% in the conservative group versus 44% in the intervention group. For episodes in the 6.0-10.0 INR range, the rate of major bleeding was 0% in the intervention group, and 0.8% (P<0.02) in the conservative group. The corresponding figure for the 10.0-20.0 range was 0% in both groups. A higher percentage of episodes with an unknown cause of excessive anticoagulation was found in the conservative management group than in the intervention group.
The study revealed that conservative management was effective in preventing major bleeding in 99% of episodes and phytonadione therapy was 100% effective.
Measure of benefits used in the economic analysis
Incidence of major bleeding was the main benefit measure.
The quantities of resource use were reported separately from the costs. The costs measured were those associated with hospitalizations, drug acquisition costs, physician and emergency department visits, laboratory, and telephone calls. The specific cost components of these cost elements were not reported. The cost analysis was based on actual data collected between November 1994 and August 1995, and included only the comparisons for the INRs ranges of 6.0 to 10.0, and 10.0 to 20.0 (>20.0 episodes were excluded). The price year was not clearly reported. The perspective was that of a health maintenance organisation.
One-way simple and 'best-scenario' sensitivity analyses were conducted by varying the efficacyrate of the comparator, and by excluding the hospitalization costs in the intervention group, respectively.
Estimated benefits used in the economic analysis
For episodes in the 6.0-10.0 INR range, the rate of major bleeding was 0% in the intervention group, and 0.8% (P<0.02) in the conservative group. The corresponding figure for the 10.0-20.0 range was 0% in both groups.
The costfor the 6.0-10.0 and the 10.0-20.0 INRs were $111.41 and $152.65 per episode, respectively for the comparator, and $802.70 and $346.64 for the intervention.
Synthesis of costs and benefits
The synthesis of costs and benefits was presented only for the 6.0-10.0 INR range since for the other range the comparator was a weakly dominant strategy. The incremental cost per major bleeding avoided after the initiation of the intervention was $70,540 (relative to the comparator or conservative-management option). The sensitivity analyses for the scenarios to which the 1.5% and 1.95% incidence rates of major bleeding applied, yielded figures of $47,240 and $35,400, respectively. The exclusion of hospitalization costs in the intervention group (due to extension of deep venous thromboembolism, in one case, and administration of intravenous heparin, in another) yielded an incremental cost-effectiveness ratio figure of $13,500.
Conservative management was shown to be safe and cost-effective when the INR was between 6.0-10.0. Based on the present and previously published study findings the American College of Chest Physicians' recommendation of phytonadione administration to patients with INRs ranging from 6.0 to 10.0 may be unnecessary, and conservative management appears to be a reasonable option.
CRD COMMENTARY - Selection of comparators
The choice of comparator was not explicitly justified by the authors. You, as a user of this database, should consider whether this is a widely used health technology in your own setting.
Validity of estimate of measure of benefit
Lack of randomisation casts doubts on the internal validity of the results.
Validity of estimate of measure of cost:
The quantities of resource use were reported separately from the costs and adequate details of methods of cost estimation were given.
Given the lack of randomisation and statistical analysis of the costs, the results may need to be treated with some caution. The conclusions reached by the authors may not be justified, given the uncertainties in the data. The issue of generalisability to other settings or countries was not addressed.
Implications of the study
Further studies are needed to validate the evidence for the cost-effectiveness of the strategies compared in this study. To this end, randomized controlled trials would be desirable.
Lousberg T R, Witt D M, Beall D G, Carter B L, Malone D C. Evaluation of excessive anticoagulation in a group model health maintenance organization. Archives of Internal Medicine 1998; 158: 528-534
Subject indexing assigned by NLM
Aged; Anticoagulants /administration & Cost-Benefit Analysis; Drug Utilization Review; Female; Guideline Adherence; Health Maintenance Organizations /economics /standards; Hemorrhage /chemically induced /economics; Humans; International Normalized Ratio; Male; Middle Aged; Societies, Medical; United States; dosage /adverse effects
Date bibliographic record published
Date abstract record published