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MOMs (multiples of the median) and DADs (discriminant aneuploidy detection): improved specificity and cost-effectiveness of biochemical screening for aneuploidy with DADs |
Evans M I, Chik L, O'Brien J E, Chin B, Dvorin E, Ayoub M, Krivchenia E L, Ager J W, Johnson M P, Sokol R J |
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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 Biochemical screening for Down's Syndrome using single, double or triple tests.
Economic study type Cost-effectiveness analysis.
Study population Pregnant women with various characteristics in the US.
Setting Medical centre/hospital. The economic study was based in New Jersey and Michigan, USA.
Dates to which data relate No dates relating to effectiveness, costing or prices were given.
Source of effectiveness data Link between effectiveness and cost data Costing was not undertaken on the same patient sample as the effectiveness study.
Study sample 24,504 consecutive cases of biochemical screening that had complete patient follow-up were analysed. Information on the result of pregnancy was obtained from physicians by questionnaire and with follow-up phone calls. After exclusion of patients with other abnormalities not under study, 23,838 patients were studied for single screening, 17,042 for double screening and 7829 for triple screening. Statistical evaluation was conducted in 3 phases.
Study design This was a large case series study from data collected at two laboratories. No loss to follow-up was reported.
Analysis of effectiveness The outcomes analysed were the sensitivity of the tests, percentages at risk, number of cases detected according to the different cut-offs and statistical methods used.
Effectiveness results Keeping the percentages at risk constant, detection frequencies were similar in both the Glasgow and the Gaussian methods (ranging from 68% to 75%), but the risk threshold was substantially higher for the Gaussian method. Single-screening detected substantially less cases than double and triple screening (25-43% compared with 61-71% and 79-86%), given different cut-off points. The DAD model increased specificity at each level of sensitivity by a range of 1-3%, compared with the MOM approach.
Clinical conclusions The Gaussian double formula was inferior to the Glasgow double approach in detecting Down's syndrome cases. Also there was no difference in the detection rates between the Glasgow double and the Gaussian triple approaches (thus adding estriol as part of the screening process is not justified). The DAD approach may improve screening by reducing the percentage at risk.
Modelling Statistical modelling was used to estimate costs and benefits.
Measure of benefits used in the economic analysis Direct costs The costs were not referenced and there was no information on their source or method of calculation. The cost per amniocentesis procedure was given as was the cost of screening. No price dates were given. Costs and quantities were not reported separately.
Indirect Costs Cost of caring for an infant with Down's syndrome.
Sensitivity analysis No sensitivity analysis was performed on the costs but modelling and sensitivity analyses were performed on the biochemical data.
Estimated benefits used in the economic analysis Keeping the percentages at risk constant, detection frequencies were similar in both the Glasgow and the Gaussian methods (ranging from 68% to 75%), but the risk threshold was substantially higher for the Gaussian method. Single-screening detected substantially less cases than double and triple screening (25-43% compared with 61-71% and 79-86%), given different cut-off points. The DAD model increased specificity at each level of sensitivity by a range of 1-3%, compared with the MOM approach.
Cost results The average cost of an amniocentesis was put at $1600. The cost of a triple screen was assumed to be $100 and a $20 saving per case was assumed for not using estriol. The cost of caring for a child with Down syndrome was suggested to be $400,000.
Synthesis of costs and benefits In a series of 25,000 patients assuming 71% sensitivity and 6% amniocentesis, the cost per case detected would be $166,970. Not using estriol, this cost drops to $149,928. An increase of 1-3% in specificity of using DADs would reduce the number of unnecessary amniocenteses and save between $400,000 and $1,200,000.
Authors' conclusions Double screening was equally as effective as triple screening and was cheaper. The DADs method needs to be researched by other groups but looks promising in terms of reducing costs and improving specificity with no change in sensitivity.
CRD Commentary The results on the sensitivity and specificity of the tests appear valid. The risk of pregnancies was comparable between groups. However, this needs to be tested on a different data set than the one on which it was estimated. Confidence intervals are also needed because the abnormalities are relatively rare. The costing data were poorly documented with no data on the sources, dates or methods being provided. The generalisability of these results is unclear and it needs to be replicated.
Bibliographic details Evans M I, Chik L, O'Brien J E, Chin B, Dvorin E, Ayoub M, Krivchenia E L, Ager J W, Johnson M P, Sokol R J. MOMs (multiples of the median) and DADs (discriminant aneuploidy detection): improved specificity and cost-effectiveness of biochemical screening for aneuploidy with DADs. American Journal of Obstetrics and Gynecology 1995; 172(4 Part 1): 1138-1149 Indexing Status Subject indexing assigned by NLM MeSH Adolescent; Adult; Aneuploidy; Biomarkers /analysis; Chorionic Gonadotropin /analysis; Chorionic Gonadotropin, beta Subunit, Human; Cost-Benefit Analysis; Discriminant Analysis; Down Syndrome /diagnosis /genetics; Estriol /analysis; Female; Genetic Testing /economics /methods; Humans; Middle Aged; Models, Statistical; Normal Distribution; Peptide Fragments /analysis; Pregnancy; Prenatal Diagnosis /economics /methods; Risk Assessment; Sensitivity and Specificity; alpha-Fetoproteins /analysis AccessionNumber 21995000600 Date bibliographic record published 31/10/1997 Date abstract record published 31/10/1997 |
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