ABSTRACT: Cell-free fetal DNA (cffDNA) testing is validated for detecting Down syndrome (DS) and trisomies 18 and 13 in high-risk populations. Because cffDNA testing can decrease invasive diagnostic testing rates with its significantly reduced false-positive rate, it potentially could improve the safety of prenatal screening and diagnosis of DS. This study reports the outcomes of an economic model that was developed to examine the costs and performance outcomes associated with the introduction of cffDNA testing in Ontario.
An algorithm of the current prenatal screening program for DS in Ontario was developed to analyze the performance and costs of this program. A modified algorithm was then developed, incorporating cffDNA testing after a positive first-trimester screening. The uptake rate of prenatal screening for DS, the screen positive rate, amniocentesis uptake rates after a positive screen, and screening performance were based on the most recent observed rates of these parameters in Ontario. Cost and performance outcomes were estimated for 8 different potential scenarios varying the primary screening test for DS or using cffDNA as a secondary screening test contingent on the primary screening test. The scenarios also varied screening test uptake based on ease and quality of test. Performance outcomes included the total number of amniocenteses performed, the total number of cases of DS detected prenatally, and the total number of iatrogenic pregnancy losses after amniocentesis on pregnancies not affected by DS. Cost outcomes included the total cost of the various programs, cost per woman screened, and cost per case of DS detected.
Use of cffDNA testing as a second-tier test was associated with a significant reduction in the number of diagnostic amniocenteses performed and a decrease in iatrogenic pregnancy loss without a significant increase in total program cost based on the current cost of $795 for the cffDNA test. Optimized first-trimester screening performance and increased screening uptake would increase the total program cost and the cost per women screened but would reduce the cost per case of DS diagnosed prenatally. The cost for each additional case of DS diagnosed prenatally was $21,900 compared with $112,919 per case of DS diagnosed in the current system. With its current price, cffDNA as a primary screening test for DS would markedly increase the overall program cost, the cost per women screened, and the cost per case of DS diagnosed. If the uptake of screening remained the same, the total program cost using cffDNA as a primary screening test would be 4.9 times that of the current program. The cost per women screened and the cost per case of DS diagnosed would be 4.9 and 2.5 times higher, respectively.
These results suggest that a prenatal DS screening system may benefit from secondary cffDNA testing that would reduce the need for invasive tests with only a small reduction in cases diagnosed and still maintain the use of the 11- to 13-week scan. However, such improved screening would lead to increased costs. Whether these additional costs are worth the improved screening needs further examination.