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Opportunistic discovery of occult disease by use of test panels in new, symptomatic primary care outpatients: yield and cost of case finding |
Takemura Y, Ishida H, Inoue Y, Kobayashi H, Beck J R |
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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 Packages of tests (test panels) for the diagnosis of occult diseases were studies. The tests were divided into two groups, Essential Laboratory Tests 1 and 2 (ELT-1 and ELT-2).
The test components of the ELT-1 panel were dipstick urinalysis, C-reactive protein, erythrocyte sedimentation rate, red blood cell count, haemoglobin, haematocrit, mean red blood cell indices, white blood cell count, total protein, albumin and albumin-to-globulin ratio.
The test components of the ELT-2 panel consisted of those for the ELT-1 panel plus urine sediment, sialic acid, platelet count leukocyte differential count, serum protein fraction profile, total cholesterol, triglycerides, glucose, aspartate aminotransferase, ALT, lactate dehydrogenase, alkaline phosphate, gamma-glutamyltransferase, cholinesterase, serum urea nitrogen, creatine and uric acid.
Test defined as optional, to be ordered if necessary, were faecal occult blood test, chest X-ray, abdominal X-ray and electrocardiogram.
Adjusted ELT-1 tests were defined following preliminary results that combined all ELT-1 tests with some ELT-2 tests.
Study population The study population comprised new outpatients presenting between the dates of the study, who had defined symptoms and were seen by physicians. Patients referred by physicians in other medical facilities were not included.
Setting The setting was primary care. The study was conducted in Japan.
Dates to which data relate The effectiveness data were collected between June 1991 and March 1997. The dates during which the resource data were collected were not reported. A price year was not given.
Source of effectiveness data The effectiveness data were derived from a single study.
Link between effectiveness and cost data The costing was carried out retrospectively on a different sample of patients to those in the effectiveness study.
Study sample The use of power calculations, to estimate the impact of chance on the results, was not reported. The sample included all patients presenting at the setting within the dates of the study, who were eligible according to the study population. No further exclusions were made. The sample was appropriate for the clinical question, as it included patients with defined symptoms who might have asymptomatic diseases that could be diagnosed via the panel tests. All of the patients received the ELT-2 test package. The results and efficacy of receiving the ELT-1 panel and the ELT-1 plus specific additional tests could then be estimated.
Study design The basis of the analysis was a diagnostic study. The ELT-2 test package represented the 'gold' standard diagnostic panel. The sensitivity and specificity results were reported elsewhere (see Other Publications of Related Interest), although these details were not used to supplement the current abstract. The study was conducted at two centres, the Comprehensive Medicines Clinic, National Defense Medical College Tokorozawa, Japan, and its affiliated hospital. The analysis was based on the immediate results of diagnostic tests, meaning that there was no need for patient follow-up.
Analysis of effectiveness The primary health outcomes were defined as tentative initial diagnoses, and primary and additional initial clinical diagnoses (ICDs). The primary care physician made tentative initial diagnoses from the history and physical examination alone. Primary ICDs were made after integrating the test results, and were related to the patient's chief complaint. Additional ICDs related to abnormal test results unexpectedly elicited from the enforcement of the ELT panel, and not related directly to the patient's illness.
Effectiveness results History and examination generated 633 tentative initial diagnoses among 540 patients.
The ELT-2 panel identified 692 primary ICDs and 276 additional ICDs.
The ELT-1 panel uncovered 79 additional ICDs.
The ELT-1 panel identified 0.15 diseases per patient (0.31 - 0.082 depending on the disease).
The ELT-2 panel identified 0.51 diseases per patient (1.1 - 0.40 depending on the disease).
Clinical conclusions The authors did not draw any effectiveness conclusions independently from the cost conclusions. Nevertheless, it was clear that specific tests within the ELT-2 panel were identifying substantial numbers of additional ICDs.
Measure of benefits used in the economic analysis The summary measure of health benefit used was the number of occult diseases per patient.
Direct costs A perspective for the cost analysis was not reported, although the costs included appear to have represented costs to the health care provider. The authors focused on expenditures required to obtain the test results. They included costs for test reagents and analyser operation, equipment amortisation, and personnel expenses for medical technologists. The costs were derived from actual data relating to a different setting because there was a lack of data for the study setting. Appropriate comparisons and discussion were made to assess the similarities between the two settings. Discounting was not carried out since the costs were incurred immediately when the tests were carried out. Nevertheless, the costs were incurred during the full period of the study (approximately 6 years), yet a price year was not reported and the need to reflate the costs to the price year was not discussed. The unit costs and the quantities were not reported separately.
Statistical analysis of costs The costs were treated deterministically.
Indirect Costs The authors reported that the indirect costs were excluded. This is appropriate as little productive time would be lost when taking time out for testing.
Sensitivity analysis No sensitivity analyses were reported.
Estimated benefits used in the economic analysis See the 'Effectiveness Results' section.
Cost results The costs were not reported separately from the effectiveness estimates (see Synthesis of Costs and Benefits).
Synthesis of costs and benefits The cost per occult disease detected for the overall population was Y4,104 (Y1,968 - Y5,524 depending on the disease) with the ELT-2 panel and Y6,289 (Y2,934 - Y11,386 depending on the disease) with the ELT-1 panel.
The cost-effectiveness of the ELT-2 panel was best for the detection of renal or urinary tract diseases (Y1,521 per disease detected) and respiratory disease (Y2,251 per disease detected).
The cost-effectiveness of the ELT-2 panel was Y3,228 per incremental occult disease.
The addition of four tests (total cholesterol, ALT, glucose and uric acid) to the ELT-1 panel yielded a cost-effectiveness of Y2,372 per occult disease detected and Y177 per incremental disease detected.
Authors' conclusions The authors concluded "the full ELT-2 (Essential Laboratory Test-2) panel is not supported by the cost-effectiveness found in our studies".
CRD COMMENTARY - Selection of comparators The authors compared the ELT-1 and ELT-2 panels in the light of practice guidelines set down by the Japan Society of Clinical Pathology. The ELT-1 panel represented the preferred method of routine testing at the time of the study.
Validity of estimate of measure of effectiveness The basis of the analysis was a diagnostic study, which was entirely appropriate to assess the clinical efficiency of panel tests. Comparisons were made on the number of occult diseases detected, rather than on sensitivity and specificity data. An assessment based on sensitivity and specificity would have been inappropriate in this instance as the authors were not testing for a specific disease. The study sample was representative of the population. The authors provided summary results for diseases detected and broke these down according to disease category. This enables the reader to assess the benefits of tests separately, and to assess whether a specific test is more beneficial.
Validity of estimate of measure of benefit The authors used the number of occult diseases detected per patient as the summary measure of health benefit. This measure was derived directly from the effectiveness study. It seems to have been the natural measure for this study.
Validity of estimate of costs Relatively few details of the cost analysis were provided. The authors did not report the perspective adopted, making it impossible to assess whether all the relevant costs were included. The costs included would appear to represent the perspective of the health care provider, but if this was the true perspective, then overhead costs were omitted. Statistical analyses were not carried out and it is difficult to assess whether omissions or errors in the cost estimates would significantly affect the costs. However, as the tests may attract similar overhead costs, the authors may have deliberately omitted this element as it was common to both technologies. The costs were not reported separately from the quantities. A breakdown of the total costs would have been useful to improve the reader=s understanding and ability to generalise the results.
Other issues The authors discussed their results with reference to a prior study of theirs, but did not make comparisons with broader findings from other similar studies. The issue of generalisability to other settings or population was not addressed although, as there were no specific exclusion criteria, the sample is representative of many populations in a similar setting. The results were presented very thoroughly, with a breakdown of the costs and effects for different disease groups. Limitations were not discussed. These centred around the quality of the cost reporting, which limits the reader=s ability to understand the cost drivers and the applicability of the results to their own setting.
Implications of the study The authors argued that their cost-effectiveness results did not support full panel testing (ELT-2), but that basic testing with some additional specific tests might be valid and further improve efficiency. The need for further research was not explicitly discussed, although the authors did question the validity of enforcing such screening tests to all individuals, or only to those at risk. This might prove interesting for further work.
Bibliographic details Takemura Y, Ishida H, Inoue Y, Kobayashi H, Beck J R. Opportunistic discovery of occult disease by use of test panels in new, symptomatic primary care outpatients: yield and cost of case finding. Clinical Chemistry 2000; 46(8 Part 1): 1091-1098 Other publications of related interest Takemura Y, Kobayashi H, Kugai N, Sekiguchi S. The results of the 'Essential Laboratory Tests' applied to new outpatients-re-evaluation of diagnostic test items. Rinsho Byori. The Japanese Journal of Clinical Pathology. 1996;44:555-63.
Indexing Status Subject indexing assigned by NLM MeSH Adolescent; Adult; Aged; Aged, 80 and over; Ambulatory Care /economics /methods; Blood Chemical Analysis /economics; Child; Clinical Laboratory Techniques /economics; Cost-Benefit Analysis; Female; Humans; Male; Middle Aged; Primary Health Care /economics /methods; Urinalysis /economics AccessionNumber 22000006410 Date bibliographic record published 31/12/2004 Date abstract record published 31/12/2004 |
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