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A cost-effectiveness evaluation of 3 antimicrobial regimens for the prevention of infective complications after abdominal surgery |
Anderson G, Boldiston C, Woods S, O'Brien P |
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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 To prevent infective complications after abdominal surgery one of three regimens were administered intravenously (IV) at the start of anaesthesia; a single dose of cefotaxime sodium (1g); ticarcillin plus clavulanic acid (3.1g) or ceftriaxone sodium (1g).
Economic study type Cost-effectiveness analysis.
Study population Patients aged over 16, scheduled for elective or emergency abdominal surgery.
Setting The practice setting was the secondary care sector. The economic and clinical studies were carried out in Melbourne, Australia.
Dates to which data relate No date was given for resource use or effectiveness. However, ethics approval for the trial was granted in 1991. 1992 prices were used.
Source of effectiveness data Estimates for final outcomes were derived from a single study.
Link between effectiveness and cost data The operating cost calculation was undertaken on the same patient sample as that used in the effectiveness analysis but the costs of complications were not. Costing was undertaken retrospectively.
Study sample Power calculation determined the sample size. 1,070 patients were included in the study. Exclusion criteria included:no informed consent given, patient sensitive to penicillin, metronidazole or cephalosporin, any antibiotic administered within 48 hours of the study, pregnant, immunosuppressed, possibility of pre-existing infection or unlikely to comply with the study protocol (i.e. four week follow-up post surgery).
Study design The study was a multi-centred Randomized controlled trial. The duration of follow-up was 4 to 5 weeks. Of the elective or emergency abdominal surgery sample, there were seven groups by operation (appendectomy, colorectal (elective or emergency), esophagogastroduodenal, small-bowel, cholecystectomy and common bile duct surgery). Within each group, patients were randomly allocated to one of the three antimicrobial regimens. No loss to follow-up was reported.
Analysis of effectiveness It seems likely that the analysis was based on intention to treat, although this was not stated explicitly. Primary health outcomes measured were major and minor complication rates, with wound infection defined as pus or discharge (from which a pathogen was cultured) from the wound. Major wound infections were those leading to a delay either in hospital discharge or return to normal activities. Wounds were considered minor when the infection did not result in delay of hospital discharge or return to normal activities. Other outcomes noted were other wound problems and infection complications such aschest infection, peritoneal infection, septicaemia and febrile morbidity.
Effectiveness results The overall wound infection rate was 4.3% (2% major infection and 2.3% minor) with a further 2.5% rate for other wound complications. There was no significant difference in the rate of major wound infections between the three test groups. The ceftriaxonesodium group had a minor wound infection rate of 0.5% rate against 2.8% in the cefotaxime sodium group, (p=0.03). The corresponding rate for the ticarcillin plus clavulanic acid group was 3.7% (difference, p=0.002). No significant difference was found with respect to rate of other wound complications between groups. With respect to other infective complications there was no significant difference between the strategies. Two events occurred that could have been toxic reactions to drug therapy but both were rapidly resolved.
Clinical conclusions The three drug regimens proved to be equally effective in the prevention of a range of complications. The only significant difference between the drug regimens was in the frequency of minor wound infections. By definition these did not cause an increased length of hospital stay or a delay in return to normal activities and therefore were not regarded as an important health issue.
Measure of benefits used in the economic analysis Since the clinical analysis showed no difference in benefits between strategies, the economic analysis was based on the difference in costs only.
Direct costs As the duration of the study follow-up was less than one year, discounting was not applied. Quantities were not reported separately from costs. The costs measured were operating costs and costs of complications. The boundary adopted was the hospital. The costs were based partly on actual data and partly on standard prices (DRGs). The authors assumed that all patients with infections were clinically similar and therefore that resource use was relatively homogenous across these patients. The number of infective complications was derived from the medical records of patients, and the elements of cost of complications was taken from the Manual of ResourceItems and Their Associated Costs (Australian Department of Health). Drug costs were those of the Alfred Group Pharmacy. The cost of equipment used and nursing time was provided from the study records. 1992 prices were used.
Statistical analysis of costs Currency Australian dollars (Aus$).
Sensitivity analysis No sensitivity analysis was performed.
Estimated benefits used in the economic analysis The overall wound infection rate was 4.3% (2% major infection and 2.3% minor) with a further 2.5% rate for other wound complications. There was no significant difference in the rate of major wound infections between the three test groups. The ceftriaxonesodium group had a minor wound infection rate of 0.5% rate against 2.8% in the cefotaxime sodium group, (p=0.03). The corresponding rate for the ticarcillin plus clavulanic acid group was 3.7% (difference, p=0.002). No significant difference was found with respect to rate of other wound complications between groups. With respect to other infective complications there was no significant difference between the strategies.
Cost results The total operating costs per patient were as follows:
cefotaxime Aus$14.31;
ticarcillin plus clavulanic acid, Aus$14.34;
ceftriaxone Aus$23.21.
The total wound infection costs per episode were Aus$14,814 for cefotaxime, Aus$22,221 for ticarcillin plus clavulanic acid and Aus$14,814 for ceftriaxone.
Synthesis of costs and benefits No synthesis was undertaken because the benefits across treatments were estimated to be very similar and therefore the economic study was based on a cost-minimization analysis.
Authors' conclusions The authors argued that the operating costs of cefotaxime and ticarcillin plus clavulanic acid are equal and significantly less than ceftriaxone. As they reported no important differences in the frequency with which infective complications occurred between regimens a cost-minimization analysis was performed. The analysis of costs for infective complications indicated that savings in the direct (operating) cost of drugs might be counteracted by greater cost of illness. The authors advocated that the cost of a single infective complication, such as a major wound infection, would negate the savings achieved by using the least expensive drug. They argued that there is "a risk that undue focus on the direct (operational) costs is inappropriate, even when minor differences in effective complications are present". Therefore, the authors argued that "the costs per episode of infective illnesses associated with the two cephalosporins were estimated to be equal" and with the operating costs of cefotaxime being lower, "it should be the preferred agent of the three trial drugs".
CRD COMMENTARY - Selection of comparators Given that there is "a wide range of possible antimicrobial regimens" it is not clear why the three regimens chosen were selected.
Validity of estimate of measure of benefit The clinical study was well conducted, with a rigorous treatment of materials and methods and clear end points. The internal validity of the study appears to be strong.
Validity of estimate of costs The cost analysis was less transparent than the clinical study. For example, the dates of the price data for operating costs were not reported. The assumption of homogeneity in costs between complicated cases may be debated.
Other issues The issue of generalisability to other settings was discussed. However, more rigorous testing is required for the results to be generalised.
Bibliographic details Anderson G, Boldiston C, Woods S, O'Brien P. A cost-effectiveness evaluation of 3 antimicrobial regimens for the prevention of infective complications after abdominal surgery. Archives of Surgery 1996; 131(7): 744-748 Other publications of related interest Comment in: Archives of Surgery 1997;132(3):320-1.
Indexing Status Subject indexing assigned by NLM MeSH Anti-Bacterial Agents /economics /therapeutic use; Cefotaxime /economics /therapeutic use; Ceftriaxone /economics /therapeutic use; Cephalosporins /economics /therapeutic use; Clavulanic Acid; Clavulanic Acids /economics /therapeutic use; Cost-Benefit Analysis; Gastrointestinal Diseases /economics /surgery; Humans; Penicillins /economics /therapeutic use; Prospective Studies; Surgical Wound Infection /economics /prevention & Ticarcillin /economics /therapeutic use; control AccessionNumber 21996000771 Date bibliographic record published 30/06/1999 Date abstract record published 30/06/1999 |
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