Bert Gold bgold at itsa.ucsf.edu
Sat Jan 13 21:29:23 EST 1996

Clinicians interested understanding and applying psychosocial
 AND medical economic considerations to the current
high level of amniocentesis being carried out on the basis
of Advanced Maternal Age, may be interested in the following abstract:
(I found these ideas fascinating)

Bert Gold,Ph.D. UCSF, Program in Medical Genetics

Y Shahar, JW Egar and R Pichumani 
Section on Medical Informatics, Stanford University School of Medicine,
Stanford, CA.
    We present two models that guide clinicians and parents who must decide
whether to perform amniocentesis (AC) for detection of fetal abnormalities:
a personal utility model for parents, and a cost benefit model for a
health-care provider. These models can tailor general guidelines to specific
AC decisions.
   The American College of Obstetricians and Gynecologists (ACOG) provides
separate guidelines, mainly concerning the use of AC and of high-resolution
ultrasound (HRUS), for detection of Down's syndrome (DS) and neural-tube
defects (NTD's). We used influence diagrams to model two decisions: (1) the
parent's decision,  using preference probabilities as personal utility
measures; and (2) the decision of a policy-making organization,
such as a large health-care organization, using monetary utility measures
for test costs and for the values of life and disability. In both cases,
we tailor the model to the particular case by using parent-specific prior
probabilities for DS and NTD, as well as the probability for miscarriage
due to the AC procedure
     The results of the analysis indicate significant sensitivity of the AC
decision to parent specific utilities. Such utilities have been elicited by
researchers such as Pauker and colleagues, and have been shown to vary 
widely. The AC decision also is sensitive to the rate of miscarriage caused
by the AC procedure, but is sensitive to the DS prior probability (e.g., by
age) only for certain personal-utility values. The NTD's prior probability 
plays a significant role mainly in cases where the decision is otherwise not
obvious. In the case of the model using monetary measures, break-even points
for the health-care provider can be shown for all three case-specific prior
probabilities, given the value of life and the cost of lifelong disability.
     The AC decision is affected by parent-specific personal utilities and
prior probabilities for DS and NTD's, and by local rates of miscarriage due
to AC. Monetary utility measures can be used in the case of a large-scale
policy. Both measures of utility might be combined, maximizing societal and
individual utilities. Using only arbitrary cutoff values (e.g. age),
considering ouly one disorder at a time, or including only one test procedure
oversimplifies the AC decision. Additional nodes, signifying relevant
parameters and utilities, can be added with relative ease to both of our
influence-diagram models. We demonstrate the need for both comprehensive data
and parent-specific utilities by a four-way sensitivity analysis and several
exemplary cases.

Discussion of this issue by netters is invited.

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