|
A comparison of two macrolide antibiotics in the treatment of community-acquired infections |
Parmar-Lapasia K, Gelone S P, Jacobs M R, Wertheimer A I |
|
|
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 Azithromycin was compared with clarithromycin in the treatment of community-acquired infections. The dosages used were not stated, but azithromycin courses were 3 to 5 days in duration and clarithromycin courses were 5 to 14 days.
Economic study type Cost-effectiveness analysis.
Study population The study population comprised patients who had been prescribed a course of either azithromycin or clarithromycin. Patients were excluded from the study if they were under 18 years, or were receiving concurrent or chronic antibiotic therapy (including azithromycin 1,200 mg/week or a single dose). Also excluded were those taking immunosuppressive medication or medication to treat human immunodeficiency virus or Helicobacter pylori.
Setting The setting was primary care. The authors did not identify the exact location, but it was likely to have been somewhere in the USA.
Dates to which data relate The effectiveness, resource use and price data were gathered for the 14 months from December 1999 to January 2001. However, the analysis was limited to data from the year 2000, with the months December 1999 and January 2001 providing background data.
Source of effectiveness data The evidence for the final outcomes was 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 study.
Study sample The authors did not report any power calculations. Investigators used prescription records to compile a database of 633 cases, which met the study inclusion criteria, from the specified period. Of the 465 prescriptions for azithromycin, 427 (92%) met the criteria of the primary objective and 38 (8%) met the criteria for the secondary objective. The remaining 168 prescriptions were for clarithromycin, of which 150 (89.3%) met the primary objective criteria and 18 (10.7%) met the secondary objective.
Study design The study employed a retrospective cohort design. The authors did not specify the number of participating sites. Data were gathered for the 14 months from December 1999 to January 2001, whereas the analysis was limited to prescriptions for the year 2000 (the months December 1999 and January 2001 provided background data).
Analysis of effectiveness The analysis of effectiveness was conducted on the basis of "therapeutic failure". This was defined as the need for a subsequent antibiotic prescription within 21 days after the initiation of azithromycin or clarithromycin for a given person. The demographic or prognostic features of the patients in the two groups were not compared.
Effectiveness results For the primary objective (when no antibiotics had been prescribed in the 21 days before receiving the study drug), the failure rate was 14.8% with azithromycin and 16% with clarithromycin. These were analysed using Student's t-test, (p=0.7137).
For the secondary objective (when there had been no response to a different antibiotic in the preceding 21 days), the failure rates were 34.2% (azithromycin) and 22.2% (clarithromycin), (p=0.3621).
Clinical conclusions The failure rates of azithromycin and clarithromycin were similar, both when no antibiotics had been prescribed in the 21 days before receiving the study drug and when there had been no response to a different antibiotic in the 21 days before receiving the study drug.
Measure of benefits used in the economic analysis The authors demonstrated statistical equivalence of the two antibiotics and, therefore, decided only to analyse cost-differences in the economic analysis.
Direct costs The direct costs incurred by the single provider, a managed care organisation, were included in the analysis. These were the costs of the study drug, other antibiotics, doctor visits and laboratory tests. The resource use data were collected retrospectively from prescription records. The actual charges made for antibiotics prescribed were collated only for those patients who had not been prescribed any antibiotics in the 21 days before receiving the study drug (the primary objective). The authors estimated the cost of a doctor's visit and a laboratory test. The costs and the resource use quantities were not reported separately. Discounting was appropriately not undertaken. The cost data were collected for the year 2000 and, although not explicitly stated, this was likely to have been the price year. The average cost for each antibiotic prescription was reported.
Statistical analysis of costs Patient-level cost data were treated as deterministic. No analysis was undertaken to examine the effect of uncertainty in the costs.
Indirect Costs The indirect costs were not included, which was appropriate given the implicit study perspective.
Sensitivity analysis A sensitivity analysis was not conducted.
Estimated benefits used in the economic analysis See the 'Effectiveness Results' section.
Cost results The total cost of azithromycin treatment was $18,603.21, compared with $12,230.38 for treatment with clarithromycin.
The average cost of azithromycin treatment was $43.56, compared with an average treatment cost of $81.53 for clarithromycin.
Synthesis of costs and benefits Authors' conclusions Clarithromycin was as effective, but twice as expensive, as azithromycin. The greater cost might have been due to the longer course of clarithromycin.
CRD COMMENTARY - Selection of comparators A justification was given for the comparator used. It represented current practice in the authors' setting. You should decide if this represents current practice in your own setting.
Validity of estimate of measure of effectiveness The analysis was based on a retrospective cohort design. However, studies using this design rely on the availability of data in the existing records, which represents a limitation to the internal validity. It was unclear whether the study sample was representative of the study population because no details of the patients were provided. In addition, the demographic or prognostic features of the patients in the two groups were not compared at analysis. It is possible that the two groups varied in a systematic way that determined which antibiotic they were prescribed, thus biasing the results. No power calculations were reported, thus it is not possible to ascertain whether the results obtained were due to the intervention or to chance.
Validity of estimate of measure of benefit As the effectiveness analysis demonstrated that the two treatments were equally effective, only the costs were assessed further. The reader is thus referred to the comments in the 'Validity of estimate of measure of effectiveness' field (above).
Validity of estimate of costs The analysis of the costs was performed from the perspective of a single provider. It appears that all the relevant categories and unit costs have been included in the analysis. The costs and the quantities were not reported separately, thus limiting the reproducibility of the study in other settings. No statistical analyses of either the quantities or prices were performed. Charges were used to proxy prices and, since they do not reflect the true opportunity costs, this may limit the generalisability of the study. The price year was not explicitly stated, thus hindering future reflation exercise
Other issues The authors compared their effectiveness findings with those from other studies, and found them to be in agreement. The issue of the generalisability of the results to other settings was not directly addressed. The authors do not appear to have presented their results selectively. The study involved adults who were not immunocompromised or receiving other antibiotic therapy or treatment for Helicobacter pylori, but the conclusions were generalised to all patients. The authors reported further limitations to their study. They acknowledged that they were unable to determine the indication for antibiotic treatment or cause of treatment failure from the available database. They also noted that the period of 21 days used to define therapeutic failure was chosen arbitrarily.
Implications of the study The authors did not make any recommendations for specific changes in practice as a direct result of their study. They did, however, note the need to reduce excessive antibiotic prescriptions in order to contain health care costs and minimise antibiotic resistance.
Bibliographic details Parmar-Lapasia K, Gelone S P, Jacobs M R, Wertheimer A I. A comparison of two macrolide antibiotics in the treatment of community-acquired infections. P and T 2003; 28(10): 656-665 Indexing Status Subject indexing assigned by NLM MeSH Administration, Oral; Angiotensin II /blood; Animals; Astragalus membranaceus /chemistry; Atrial Natriuretic Factor /blood; Cardiotonic Agents /administration & Drug Combinations; Drugs, Chinese Herbal /administration & Endothelins /blood; Heart Failure /blood /physiopathology; Male; Myocardial Contraction /drug effects; Ophiopogon /chemistry; Panax /chemistry; Plants, Medicinal /chemistry; Protein Precursors /blood; Rats; Rats, Sprague-Dawley; Ventricular Function, Left; Ventricular Remodeling /drug effects; dosage /isolation & dosage /pharmacology; purification /pharmacology AccessionNumber 22003008583 Date bibliographic record published 31/10/2005 Date abstract record published 31/10/2005 |
|
|
|