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Analisis de costes farmacologicos en el tratamiento de la hipertension arterial: aproximacion a un estudio coste-efectividad [Analysis of pharmacological costs in the treatment of arterial hypertension: approximation to a cost-effectiveness study] |
Alonso Moreno F J, Garcia Palencia M, Laborda Peralta M, Hermoso Lopez A, Lopez de Castro F |
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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 The use of different drug therapies for the treatment of arterial hypertension. The antihypertensive therapies were classified as monotherapies or combined therapies. The monotherapies included diuretics, calcium-channel blockers, and angiotensin-converting enzyme (ACE) inhibitors. The combined therapies including diuretics plus ACE inhibitors, diuretics plus calcium-channel blockers, calcium-channel blockers plus ACE inhibitors, beta-blockers, and alpha-blockers.
Economic study type Cost-effectiveness analysis.
Study population The study population comprised patients older than 14 years of age who required antihypertensive therapy.
Setting The setting was a rural health centre, but the interventions could be performed in primary care. The study was carried out at the Centros de Salud de Yepes and Ocana, Toledo, Spain.
Dates to which data relate The effectiveness and resource use data were gathered from July 1995 to June 1996. The price year was 1996.
Source of effectiveness data The effectiveness data were derived from a single study.
Link between effectiveness and cost data The costing was undertaken retrospectively on the same patient sample as that used in the effectiveness analysis.
Study sample Power calculations were performed in the planning phase of the study. It was assessed that a sample of 211 patients would have been required to detect a statistically significant difference between the costs of the treatments. Patients presenting at the hospitals where the study was conducted, during the study period, were included in the analysis. Of the 231 patients identified, 15 patients (6.5%) were excluded for the following reasons:
they did not undergo antihypertensive therapy for at least 3 months;
they did not comply with the scheduled control visits;
they did not report drug use and doses in the clinical record; or
the treatment was interrupted or modified during the study period.
The patients excluded did not differ from those who remained in the study. The final sample was composed of 216 patients with an average age of 68.6 years (standard deviation, SD=9.9; range: 30 - 99), of which 143 (68.4%) were women. The number of patients in each study group was:
45 for diuretics,
62 for calcium-channel blockers,
45 for ACE inhibitors,
19 for diuretics plus ACE inhibitors (planned association),
13 for diuretics plus ACE inhibitors (no planned association),
11 for diuretics plus calcium-channel blockers,
6 for calcium-channel blockers plus ACE inhibitors,
3 for beta-blockers,
3 for alpha-blockers, and
9 in other groups.
Study design This was a retrospective case-control study carried out in two rural centres in Spain. The length of follow-up was unclear, but appears to have been that of the study period. The loss to follow-up was not specified.
Analysis of effectiveness All patients included in the final sample were accounted for in the analysis. The primary health outcomes used in the analysis were:
the systolic blood pressure (SBP) and diastolic blood pressure (DBP) values in the patient sample;
the percentage of patients following any monotherapy or combined therapy;
the percentage of patients responding to the treatment; and
the average reduction in the blood pressure (BP) values after the therapy.
Statistical analyses were conducted to show the comparability of the groups in terms of their cardiovascular risk factors. Only the number of patients with diabetes mellitus was statistically different. It was higher in the groups of patients treated with calcium-channel blockers or ACE inhibitors.
Effectiveness results The mean value of SBP in the overall patient sample was 172.6 (+/- 16.2) mmHg before the treatment and 141.3 (+/- 13) mmHg after the treatment, (p<0.0001). The mean value of DBP was 98.7 (+/- 11.4) mmHg before the treatment and 84.3 (+/- 6.8) mmHg after the treatment, (p<0.0001).
The percentage of patients following any of the monotherapies was 73.6% (159 patients). The remainder followed any of the combined therapies (25.9% used two drugs and 0.05% used three drugs).
The more frequently used monotherapy was calcium-channel blockers, whilst the most frequently used combined therapy was diuretics plus ACE inhibitors.
The percentages of patients responding to the therapy were:
46.6% for diuretics,
35.5% for calcium-channel blockers,
31.1% for ACE inhibitors,
26.3% for diuretics plus ACE inhibitors (planned association),
38.5% for diuretics plus ACE inhibitors (no planned association),
9.1% for diuretics plus calcium-channel blockers,
16.6% for calcium-channel blockers plus ACE inhibitors,
33.3% for beta-blockers, and
33.3% for alpha-blockers.
However, the authors stated that the differences in the percentages of patients well-controlled were not statistically significant.
Finally, in terms of the average reduction in BP, all drug therapies significantly reduced the SBP and DBP values in each group. The greatest reductions were achieved by the diuretic monotherapy and calcium-channel blocker monotherapy.
Clinical conclusions The effectiveness of the drug therapies was quite high in almost all cases. The diuretics appear to have been slightly more effective than the remaining therapies, both in terms of the proportion of responsive patients and the overall reduction in BP.
Measure of benefits used in the economic analysis The benefit measures used in the economic analysis were two intermediate outcome measures derived from the effectiveness analysis. These were the number of patients responding to the therapy and the reduction in BP.
Direct costs Discounting was irrelevant due to the short time horizon of the study. Only the average monthly cost of the drug regimes was included in the analysis. This was obtained from the drug dosage prescribed and reported in the patients' clinical records, and the drug prices for 1996. Other direct costs, such as visits and further examinations, were not included because they were assumed to be the same among all treatments. The unit costs were not reported. The resource/cost boundary was not reported. The quantities of resource use were gathered from July 1995 to June 1996. The price year was 1996.
Statistical analysis of costs No statistical analysis was reported.
Indirect Costs The indirect costs were not included.
Sensitivity analysis No sensitivity analysis was conducted.
Estimated benefits used in the economic analysis See the 'Effectiveness Results' section.
Cost results The average monthly cost per patient (regardless of the drug therapy) was Pta 2,574 (SD=1,966). The average monthly cost per patient was:
Pta 455 (SD=156) for diuretics,
Pta 2,809 (SD=1,585) for calcium-channel blockers,
Pta 2,947 (SD=1,268) for ACE inhibitors,
Pta 3,259 (SD=564) for diuretics plus ACE inhibitors (planned association),
Pta 3,697 (SD=966) for diuretics plus ACE inhibitors (no scheduled association),
Pta 3,763 (SD=2,701) for diuretics plus calcium-channel blockers,
Pta 7,556 (SD=1,180) for calcium-channel blockers plus ACE inhibitors,
Pta 517 (SD=237) for beta-blockers, and
Pta 1,257 (SD=Pta 1,355) for alpha-blockers.
Synthesis of costs and benefits The costs and the benefits were combined by calculating the following cost-effectiveness ratios:
the cost per case controlled (monthly cost multiplied by the patients treated, divided by the number of patients responding); and
the cost per mmHg reduction in BP (monthly cost multiplied by the patients treated, divided by the average reduction in BP).
No incremental analysis was performed. The cost per case responding to the treatment was particularly high for ACE inhibitors (Pta 9,472) and for calcium-channel blockers (Pta 7,916). The diuretics proved to be the cheapest therapy (Pta 975). As a consequence, the combined therapy including ACE inhibitors was highly expensive. The costs per mmHg reduction in SBP and DBP were:
Pta 13 and Pta 30.5 for diuretics;
Pta 83.6 and Pta 163.3 for calcium-channel blockers;
Pta 101.6 and Pta 346.7 for ACE inhibitors;
Pta 103.8 and Pta 202.4 for diuretics plus ACE inhibitors (planned association);
Pta 122 and Pta 271.8 for diuretics plus ACE inhibitors (no scheduled association); and
Pta 144.7 and Pta 235.1 for diuretics plus calcium-channel blockers.
Authors' conclusions The average cost-effectiveness ratios were high for angiotensin-converting enzyme (ACE) inhibitors and calcium-channel blockers, and relatively low for diuretics.
CRD COMMENTARY - Selection of comparators The selection of the comparators was not explicitly justified. It appears that all the drug therapies represented possible treatments available for the treatment of arterial hypertension. You should consider whether they represent commonly used technologies in your own setting.
Validity of estimate of measure of effectiveness The effectiveness analysis used data derived from a case-control study with a retrospective design. Power calculations were performed, but only to detect statistically significant differences in terms of the costs, not the effectiveness. In fact, no significant difference was found among the drugs in terms of the number of responsive patients. Further, very few cases of patients treated with beta-blockers were available, although the literature has shown that both beta-blockers and diuretics are the most efficacious drug regimens in reducing both morbidity and mortality in arterial hypertension. Finally, only the short-term effects of the treatments were considered in the study. The authors noted that it would have been more interesting to assess long-term efficacy.
Validity of estimate of measure of benefit No summary health benefit measure was used because no other data were easily available. The authors noted that the intermediate outcomes measures were quite commonly used in the case of patients with arterial hypertension.
Validity of estimate of costs The perspective of the study was not reported and it was unclear who bore the costs of the treatment. Only the costs of the drugs were included in the analysis, while the other direct and indirect costs were assumed to be similar. The unit costs were not reported and the costs were treated deterministically.
Other issues Since the drug therapies were not statistically different in terms of the cases responding to the treatment, and only slightly different in terms of the reduction in BP, the cost of the drug was the crucial variable in the determination of the cost-effectiveness ratio. Therefore, diuretics were the cheapest and most cost-effective treatment. In addition, a possible limitation of the study was that an incremental analysis was not performed. The authors compared their results with those from other studies. The generalisability to other settings was quite limited due to the lack of sensitivity analyses.
Implications of the study The authors stated that some caution is necessary when implementing the study results to the real practice of treating patients with arterial hypertension. However, it appears that primary care physicians should consider not only the effectiveness, but also the cost-effectiveness of the different antihypertensive treatments considered in the study.
Bibliographic details Alonso Moreno F J, Garcia Palencia M, Laborda Peralta M, Hermoso Lopez A, Lopez de Castro F. Analisis de costes farmacologicos en el tratamiento de la hipertension arterial: aproximacion a un estudio coste-efectividad. [Analysis of pharmacological costs in the treatment of arterial hypertension: approximation to a cost-effectiveness study] Atencion Primaria 1998; 21(9): 607-612 Indexing Status Subject indexing assigned by NLM MeSH Adult; Aged; Aged, 80 and over; Antihypertensive Agents /economics /therapeutic use; Cost-Benefit Analysis; Drug Costs; Female; Humans; Hypertension /drug therapy /economics; Male; Middle Aged; Spain AccessionNumber 21998006951 Date bibliographic record published 30/09/2002 Date abstract record published 30/09/2002 |
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