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Effect of computed tomography on patient management and costs in children with suspected appendicitis |
Garcia Pena B M, Taylor G A, Lund D P, Mandl K D |
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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 Three different strategies for using computed tomography (CT) to diagnose and manage children with suspected appendicitis were studied. The diagnostic strategies proposed were:
to obtain CT scans on all children who were to be admitted for observation, and to discharge home all those with negative CT scans (CThome);
to obtain CT scans on all children who were to be admitted for observation, and to admit all with negative CT scans (CTadmit);
to obtain CT scans selectively on all children who were to be admitted for observation with a peripheral white blood cell (WBC) greater than 10,000/mm3 (10 x 10^9/L), and to admit all with negative CT scans (WBCCTadmit).
Economic study type Cost-effectiveness analysis.
Study population The study population comprised children admitted to the hospital with possible appendicitis.
Setting The setting was a hospital. The economic study was carried out in Boston (MA), USA.
Dates to which data relate The data for the effectiveness analysis were collected between January 1996 and August 1997 (20-month period). The resource quantities were collected during the same period. The price year was 1997.
Source of effectiveness data The effectiveness data were derived from a single study.
Link between effectiveness and cost data The resource quantities were obtained retrospectively from the same sample as that used in the effectiveness study. The prices applied to these resource quantities were obtained from the hospital charge database.
Study sample No power calculations to determine the sample size were performed. All patients admitted to the emergency department of the hospital for suspected appendicitis during the study period, who did not have a definitive diagnosis of appendicitis, were included in the analysis. Among 620 patients admitted to the hospital during the study period, 308 were included in the analysis. Their mean age was 10.9 years (standard deviation = 4.9 years; range: 0.5 - 25.0) and 53.9% were female. A total of 75 patients admitted to the hospital for suspected appendicitis had a CT scan performed. The authors did not report evidence that the initial study sample was representative of the study population. Those patients who were admitted directly to the operating room, or who were discharged home from the emergency department, were excluded.
Study design This was a retrospective cohort study using the hospital database. The study was conducted at a single centre. The authors noted the lack of follow-up for all the patients sent home after their admission. Therefore, some may have been treated in another institution.
Analysis of effectiveness The authors did not state whether the basis of the analysis of the clinical study was intention to treat or treatment completers only. It would appear to have been conducted on the basis of treatment completers. The primary health outcomes analysed for each strategy were:
the number of CTs performed;
the number of inpatient observation days;
the number of cases of appendicitis and missed appendicitis;
the total number of operations performed;
the number of negative laparotomies; and
the sensitivity and specificity of the CT scans for the patients included in the analysis.
When compared with those patients who did not have CT scans, patients who had CT scans were shown to be comparable at analysis in terms of their age (11.3 years versus 10.7 years), (p=0.26), and rates of appendicitis (57% versus 59%), (p=0.83). The rate of perforation was higher in the subgroup that had CT scans performed (97% versus 22%), (p<0.01).
Effectiveness results The number of CTs performed was 58 (19%) for current practice, 308 (100%) for CThome, 308 (100%) for CTadmit, and 173 (56%) for WBCCTadmit (percentages were not shown in the analysis).
The number of inpatient observation days was 487 for current practice, 0 for CThome, 363 for CTadmit, and 370 for WBCCTadmit. The number of cases with appendicitis was not given in the original paper. However, the writer of this abstract calculated it to be 86, by subtracting the number of negative laparotomies from the number of operations.
The number of missed appendicitis cases was 3 for current practice, 3 for CThome, 0 for CTadmit, and 2 for WBCCTadmit.
The total number of operations performed was 112 for current practice, 93 for CThome, 93 for CTadmit, and 97 for WBCCTadmit.
The number of negative laparotomies was 26 (23%) for current practice, 7 (8%) for CThome, 7 (8%) for CTadmit, and 11 (11%) for WBCCTadmit, (percentages were not shown in the analysis).
The sensitivity of the CT scans was 97% (95% confidence interval, CI: 0.92 - 1.00), while the specificity was 97% (95% CI: 0.89 - 1.00).
Clinical conclusions In terms of effectiveness, the proposed strategies presented better clinical results in the diagnosis and management of children with suspected appendicitis, compared with current practice. The proposed strategies resulted in reduced numbers of days of inpatient observation, operations, and negative laparotomies. The best strategy to follow is CTadmit, as it presents the same proportion of negative laparotomies and total operations as those for CThome and WBCCTadmit, but it does not miss any cases of appendicitis. However, the total number of impatient observation days is much higher than for the CThome strategy.
Modelling A decision analytic model was used to estimate the outcomes and costs for the three proposed strategies, compared with the reference strategy (actual practice). The assumptions considered in the model for the three proposed strategies were:
patients with positive CT scan went directly to the operating room for appendectomy;
the procedural costs of negative laparotomy and positive laparotomy without perforation were identical;
the number of postoperative hospital days were identical for both negative and positive laparotomies without perforation;
patients sent home with a missed appendicitis would subsequently perforate; and
patients with appendicitis having a false-negative CT scan, who were then admitted, would be accurately diagnosed on the floor.
Measure of benefits used in the economic analysis A cost-consequences analysis was performed. Therefore, no summary measure of health benefit was used in the economic analysis.
Direct costs The resource quantities and the costs were reported separately. The direct costs included in the study were those relating to the acute care for the strategies considered at analysis. Those included in the analysis were for a perforated appendicitis, a nonperforated appendicitis, an inpatient observation day, an abdominopelvic CT scan, and an abdominopelvic ultrasound. The cost per inpatient observation day included the daily room cost, laboratory tests, intravenous fluids, and medication. These costs were estimated using the average charges obtained from the hospital charge database at the hospital. The average costs were calculated from the average hospital charge data using a cost-to-charge ratio of 0.72.
Discounting was not carried out. However, it would have been irrelevant given that the interventions were performed over a timeframe of less than 2 years. The price year was 1997.
The authors excluded the costs of the emergency department because they were incurred by every patient, and were independent of the strategy performed. They also omitted the costs of the supine and upright abdominal radiographs, but no justification was given for this exclusion.
Statistical analysis of costs No statistical analysis of the costs was reported.
Indirect Costs The indirect costs were not reported. However, if researchers wish to adopt a societal perspective, the indirect costs (primarily productivity losses) should be considered.
Sensitivity analysis Four one-way sensitivity analyses were performed to test the robustness of the model to changes in the sensitivity and specificity of CT (range: 80% - 100%), the costs of CT (range: $250 - $2000), and the costs of an inpatient observation day (range: $100 - $2000). The area of uncertainty investigated was variability in the data.
Estimated benefits used in the economic analysis See the 'Effectiveness Results' section.
Cost results The average cost per patient was $5,831 for current practice, $3,813 for CThome, $5,277 for CTadmit, and $5,140 for WBCCTadmit.
The incremental cost for current practice was $2,018 when compared with CThome, $554 when compared with CTadmit, and $691 when compared with WBCCTadmit.
Compared with CThome, the cost of preventing a missed appendicitis with CTadmit was $150,304. However, the authors did not state how this cost was calculated.
The sensitivity analyses showed that the ordering of the strategies remained constant through the range of variables considered. CThome was the least costly, followed by WBCCTadmit and CTadmit. Current practice was the most expensive strategy, unless the cost of CT was greater than $1,650, in which case the CTadmit strategy would become the most expensive.
The costs related to the harm produced to those patients with missed appendicitis that had finally perforated, or to those patients who did not have appendicitis and underwent negative laparotomies, were not considered in the analysis, although they were probably not relevant given the scope of the study.
Synthesis of costs and benefits Not applicable due to the cost-consequences approach adopted.
Authors' conclusions The acquisition of computed tomography (CT) scans for all children who were candidates for inpatient observation for suspected appendicitis would reduce the total number of days of inpatient prediagnosis observation, operations, and negative laparotomies. In addition, it would reduce the total cost per patient. CTadmit would result in the lowest number of missed appendicitis cases, although there would be additional costs related to hospitalisation.
CRD COMMENTARY - Selection of comparators The comparator used was justified on the grounds that it represented current practice. You should decide if this is a widely used health technology in your own setting.
Validity of estimate of measure of effectiveness The analysis used a retrospective cohort study, which was appropriate for the study question. The authors did not provide any evidence that the study sample was representative of the study population. The authors reported that some selection bias may have been present when generating the cohort of observed patients. They stated that the patient groups were shown to be comparable at analysis in terms of their age and rates of appendicitis, but children who had CT were significantly more likely to have appendiceal perforation, which may have affected the estimates of CT sensitivity and specificity. However, the sensitivity analysis performed on these parameters showed that the model was robust, with the ordering of strategies remaining constant throughout the whole range of reported sensitivity and specificity of CT.
The authors also reported that some of the patients sent home may have gone on to be diagnosed with appendicitis in another institution. The loss to follow-up of these patients may have affected the numbers of appendicitis cases and missed appendicitis cases, both in the current practice and CThome strategies, and the sensitivity of the CT scan. However, the authors stated that the hospital sees more than 60% of paediatric visits and performs approximately 50% of the paediatric surgery in the area in which the study was carried out. This fact may decrease the effect of the loss to follow-up.
Validity of estimate of measure of benefit The authors did not derive a summary measure of health benefit. The analysis was therefore categorised as a cost-consequences study.
Validity of estimate of costs The perspective of the study was not reported, although it was that of the hospital. This perspective missed some important costs, such as the cost produced to patients with negative laparotomies, or to those with missed appendicitis that perforated due to the delay. However, it would appear that the consideration of these costs would not have altered the ordering of the strategies, as current practice was the strategy with the higher percentage of negative laparotomies and missed appendicitis.
Some relevant costs were excluded from the analysis. The authors did not include the costs of the emergency department because every patient incurred them, regardless of the strategy performed. They also omitted the costs of the supine and upright abdominal radiographs, but did not justify their exclusion.
The method used to calculate the costs, based on applying a cost-to-charge ratio to the hospital's own internal cost data, has several limitations. Also, it does not necessarily provide an accurate measurement of the overall costs of the strategies. Moreover, if you, as a researcher, are concerned with a non-US hospital system, which does not routinely generate patient bills, you will have to take into account the fact that this method of estimating costs is rarely applied outside the USA.
The costs and the quantities were reported separately and the price year was given. One-way sensitivity analyses on the costs of CT and on a day of inpatient observation were performed, showing robust results for the model. This enhances the generalisability of the results to other settings. However, no statistical analysis of the quantities was performed. This limits the reliability of the conclusions because additional costs and morbidity, and even mortality, may be incurred by long-term complications of missed appendicitis. The authors stated that these complications could be expected to be reduced under any of the proposed CT strategies.
Other issues The authors made appropriate comparisons of their findings with those from other studies, but did not address the issue of generalisability to other settings.
Implications of the study Compared with current practice, obtaining CT scans in all children who are candidates for inpatient observation for suspected appendicitis reduces the number of inpatient observation days and negative laparotomies, and also the number of missed appendicitis cases (CTadmit and WBCCTadmit), therefore reducing the costs. In terms of the patients' welfare, the best strategy is CTadmit, as it reduces the number of missed appendicitis cases to zero, although it implies some additional costs related to the hospitalisation of those patients with negative CT scans.
The authors recommend not undergoing additional diagnostic procedures for those patients at either very low or very high risk of appendicitis, in order to avoid exposing them to unnecessary radiation and contrast exposure. They also recommend using CT in conjunction with an experienced paediatric surgeon in the evaluation of appendicitis.
Bibliographic details Garcia Pena B M, Taylor G A, Lund D P, Mandl K D. Effect of computed tomography on patient management and costs in children with suspected appendicitis. Pediatrics 1999; 104(3): 440-446 Other publications of related interest Garcia Pena BM, Taylor GA, Fishman SJ, Mandl KD. Costs and effectiveness of ultrasonography and limited computed tomography for diagnosing appendicitis in children. Pediatrics 2000;106:672-6.
Izbicki JR, Knoefel WT, Wilker DK, et al. Accurate diagnosis of acute appendicitis: a retrospective and prospective analysis of 686 patients. European Journal of Surgery 1992;158:227-31.
Rao PM, Rhea JT, Novelline RA. Sensitivity and specificity of the individual CT sings of appendicitis: experience with 200 helical appendiceal CT examination. Journal of Computer Assisted Tomography 1997;21:686-92.
Rao PM, Rhea JT, Novelline RA, Mostafavi AA, McCabe CJ. Effect of computed tomography of the appendix on treatment of patients and use of hospital resources. New England Journal of Medicine 1998;338:141-6.
Rao PM, Rhea JT, Novelline RA, et al. Helical CT technique for the diagnosis of appendicitis: prospective evaluation of a focused appendix CT examination. Radiology 1997;202:139-44.
Indexing Status Subject indexing assigned by NLM MeSH Appendicitis /economics /radiography /therapy; Child; Cohort Studies; Decision Support Techniques; Emergencies; Female; Hospital Costs /statistics & Humans; Male; Outcome Assessment (Health Care); Retrospective Studies; Sensitivity and Specificity; Tomography, X-Ray Computed /economics /utilization; numerical data AccessionNumber 21999001833 Date bibliographic record published 31/01/2003 Date abstract record published 31/01/2003 |
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