Cost-effectiveness model for first-trimester versus second-trimester ultrasound screening for Down syndrome

To develop a cost-effectiveness analysis model from the perspective of Medicare reimbursement to evaluate the costs and potential risks involved in performing second-trimester genetic sonography following the first-trimester sonographic measurement of nuchal translucency and serology for Down syndrome screening.

Three clinical screening algorithms were constructed that detailed the diagnostic evaluation of the target population by using first-trimester or second-trimester ultrasound and appropriate serologies or first-trimester and second-trimester screening in combination. The cost analysis was then created by using a computer spreadsheet program by applying Medicare reimbursement, the prevalence of Down syndrome, and reported sensitivities of first-trimester and second-trimester ultrasound and analytes for Down syndrome for each clinical algorithm. Medicare Current Procedural Terminology codes, total relative value units, and payments for first-trimester and second-trimester ultrasound, chorionic villous sampling, amniocentesis, and serum analytes were obtained from the Medicare Part B Washington 2002 Provider Disclosure Report.

At any given prevalence of Down syndrome, first-trimester screening is always slightly less expensive to society than the other two models for both total cost and cost to diagnose each case of Down syndrome. Even if second-trimester screening were 100% sensitive, the sensitivity of first-trimester screening would have to fall below 55% for model 2 to be cheaper than model 1. Combining both first-trimester and second-trimester screening was substantially more expensive than models 1 or 2. More iatrogenic fetal deaths occur with combined screening than with either first or second trimester screening alone.

Screening using first-trimester ultrasound and serologic markers to screen for Down syndrome is always slightly less expensive to society than second-trimester serologic and ultrasound screening. However, there is a significantly increased risk for iatrogenic fetal death if second-trimester genetic sonography is performed following normal first-trimester screening using currently accepted risk ratios. Patients should be counseled appropriately with this information, because an individual's circumstances will affect that person's perception of risk and subsequently affect his or her decision making.