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Ultrasonography improves diagnostic accuracy of acute appendicitis and provides cost savings to hospitals in Japan |
Fujii Y, Hata J, Futagami K, Hamada T, Mitsuoka H, Teramen K, Konemori G, Suenaga K |
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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 Ultrasonography was assessed as a diagnostic tool for acute appendicitis. The sonographic equipment used was a Toshiba SSA-260 A or SSA-380A, equipped with 3.5 to 5.0 MHz convex sectorial probes for the entire abdomen and 7.5 to 10.0 MHz linear probes for local examination of the affected bowel. There was no comparator technology.
Economic study type Cost-effectiveness analysis.
Study population The study population comprised patients with acute appendicitis who were either inpatients or outpatients at the study hospital. Two hundred patients with clinically suspected appendicitis were included in the study. The authors stated that none of the patients had undergone appendectomy, but did not state whether this was an exclusion criterion stated at the outset. No other inclusion or exclusion criteria were identified.
Setting The setting was secondary care. The economic study was carried out at Miyoshi General Hospital, Hiroshima, Japan.
Dates to which data relate The effectiveness data related to patients who received ultrasonography between April 1997 and March 1998. The resource use data related to the same time period. The price year was not reported.
Source of effectiveness data The effectiveness data were derived from a single study.
Link between effectiveness and cost data The costing was carried out prospectively on the same sample of patients as that used in the effectiveness study.
Study sample Power calculations to rule out the influence of chance on the results, were not reported. The sample was selected by including 200 consecutive patients treated for clinically suspect acute appendicitis at the study hospital between the dates of the study. Appendiceal ultrasonography was indicated for each of the patients. This sample was appropriate for the clinical study question since it comprised patients who required investigation for suspected appendicitis. Each of the 200 patients was assessed before ultrasonography and received ultrasonography. There were no reported refusals to participate, and no patients were excluded for any reason.
Study design The study was a diagnostic study. For each of the 200 patients, the attending physician assessed the likelihood of acute appendicitis as either "definitely appendicitis", "probably appendicitis", or "possible appendicitis". The patients were reassessed once they had received their ultrasound test and the results were available, according to the classifications "definitely", "probably" and "definitely not". The ultrasound operator was blind to the initial classification of the patient. The sensitivity and specificity of ultrasonography were assessed with reference to the actual diagnosis that was determined either during clinical follow-up or surgery (the 'gold' standard). The study was conducted at a single centre.
Analysis of effectiveness The analysis was based on the comparison of diagnosis before ultrasonography, after ultrasonography and the actual diagnosis. The primary health outcomes were the sensitivity, specificity and predictive values of ultrasound. Since there was only one patient group there was no need to assess comparability. Summary statistics of the patients involved were not reported.
Effectiveness results Fifty-seven patients were confirmed as having appendicitis.
Of these 57 patients, clinical diagnosis predicted 39 as definitely appendicitis, 15 as probable, and 3 as possible. Ultrasound predicted 52 as definitely appendicitis, 2 as probable, and 3 as definitely not appendicitis.
A total of 143 patients were confirmed as not having appendicitis.
Of these 143 patients, clinical diagnosis predicted 25 as definitely appendicitis, 44 as probable, and 74 as possible. Ultrasound predicted 0 as definitely appendicitis, 0 as probable, and 143 as definitely not appendicitis.
Ultrasound was 94.7% sensitive, 100% specific, and had 100% positive predictive value and 97.7% negative predictive power. The overall accuracy of ultrasound was 98.5%.
Clinical conclusions The authors concluded that ultrasonography has high diagnostic accuracy and improves patient care by averting unnecessary appendectomies in patients with suspected acute appendicitis.
Measure of benefits used in the economic analysis The authors did not estimate a summary measure of health benefit. The study was, in effect, a cost-consequence analysis.
Direct costs A perspective for the costing was not reported, but it appears to have been that of the hospital. The authors assessed changes in patient care as a result of ultrasonography by comparing planned treatment with the actual treatment received once ultrasound had been carried out. The authors did not report any discounting. However, as they appear to have been concerned with the immediate costs of treatment, discounting was irrelevant. The authors estimated the cost of appendectomy and the cost of a day in hospital from patients ultimately diagnosed with acute appendicitis. The cost data were obtained from the hospital's cost database (i.e. actual data). Excluded from these costs were the laboratory and radiological tests.
The unit cost of an ultrasonographic examination was reported separately. The quantities were not reported separately. The costs were estimated for the same time as the clinical study (April 1997 to March 1998). The authors' principle aim was to compare the treatment plans made before ultrasonography with the actual treatment received after ultrasonography. This enabled them to estimate the number of unnecessary appendectomies avoided, and thus the total cost avoided (including days in hospital saved). This was considered with reference to the total cost of performing the ultrasound examinations.
Statistical analysis of costs The costs were treated deterministically.
Indirect Costs The authors reported that indirect costs, including incidental charges such as bed charges and referral charges, were excluded from the estimates. There was no report that indirect costs to the patient were estimated, which may have been relevant if unnecessary ultrasound examinations were no longer performed, resulting in fewer patient days in hospital and in recovery. Since the perspective of the analysis was not stated, it is unclear whether such costs were within the scope of the current study.
Currency The costs were estimated in Japanese Yen (Y) then converted to US dollars ($). The conversion rate was $1 = Y123. The date of the conversion was not reported.
Sensitivity analysis No sensitivity analyses were reported.
Estimated benefits used in the economic analysis See the 'Effectiveness Results' section.
Cost results The total cost-savings per patient were $330 (Y40,590).
The total cost-savings for all patients in the study were $65,988 (Y8,116,524).
Synthesis of costs and benefits The costs and benefits were not combined.
Authors' conclusions "Ultrasonography performed in patients with suspected acute appendicitis improves patient care by averting unnecessary appendectomies and by averting delays before medical or surgical treatment." This consequently reduces hospital expenditure.
CRD COMMENTARY - Selection of comparators The authors compared diagnosis before and after ultrasonography with the definitive diagnosis provided by clinical follow-up and surgery. These comparisons were appropriate for the clinical question posed and no comparator technology was required. The proposed and actual treatments were compared for the costing analysis.
Validity of estimate of measure of effectiveness The study design of comparing proposed diagnoses and treatment before and after ultrasonography was ideal for the clinical question posed. The study sample was representative of the study population, as it comprised patients with clinically suspected acute appendicitis. However, only limited summary statistics of the sample were given. This will limit the comparability of the results with future potential work in the same area. Although power calculations were not reported the sample size was 200, and there were significant absolute differences in the diagnoses provided by each technique. The ultrasound operator was blinded so as to avoid bias in the interpretation of the scan results. This improves the internal validity of the results.
Validity of estimate of measure of benefit The authors did not derive a summary measure of health benefit. The analysis was, in effect, a cost-consequences study.
Validity of estimate of costs Since a perspective for the analysis was not reported, it is not possible to assess whether all the relevant costs were included. The cost estimates that were reported appear to represent the perspective of the hospital. The cost-savings per patient receiving ultrasonography were $330. Therefore, small omissions in cost may not affect the principle conclusions drawn. Some unit costs were reported separately and the authors broke down the components of the total cost-savings, which improves the reader's understanding of the key cost drivers. The price year was not reported, thus hindering any future reflation exercise.
Other issues The authors made appropriate comparisons of their results with those from other studies. They referred to studies that both supported their results and presented conflicting results. For the latter (conflicting results), there was a discussion of differences in the study designs that may have caused such conflict. The issue of generalisability of the results to other settings was not addressed. Since summary statistics of the study population were not presented, it was unclear to what extent the study population was representative of the overall area or national population. The results were not presented selectively. The conclusions accurately reflected the scope and design of the analysis, and the authors made a useful comparison with an alternative diagnostic technique available. One reported limitation was that the cost-savings estimated might have either over or under represented the true cost-savings in practice. Reasons for this were discussed, thus aiding the reader to apply the results, in theory, to their own research.
Implications of the study The authors did not make any recommendations for policy or practice as a result of their study. They did not suggest a need for further research.
Bibliographic details Fujii Y, Hata J, Futagami K, Hamada T, Mitsuoka H, Teramen K, Konemori G, Suenaga K. Ultrasonography improves diagnostic accuracy of acute appendicitis and provides cost savings to hospitals in Japan. Journal of Ultrasound in Medicine 2000; 19(6): 409-414 Other publications of related interest Ford RD, Passinault WJ, Morse ME, et al. Diagnostic ultrasound for suspected appendicitis: does the added cost produce a better outcome. American Surgeon 1994;60:895.
Indexing Status Subject indexing assigned by NLM MeSH Acute Disease; Adolescent; Adult; Aged; Aged, 80 and over; Appendicitis /ultrasonography; Child; Child, Preschool; Cost Savings; Female; Hospital Costs; Humans; Japan; Male; Middle Aged; Reproducibility of Results AccessionNumber 22001000790 Date bibliographic record published 30/06/2004 Date abstract record published 30/06/2004 |
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