Skip to main content
Fig. 2 | BMC Health Services Research

Fig. 2

From: Fetal Down syndrome screening models for developing countries; Part II: Cost-benefit analysis

Fig. 2

An example of decision tree, FTS as a part of I-S with NIPS (Model 8), shows probability and numbers of DS and non-DS group at each step of screening which could be detected or missed from the first step of acceptance/rejection of screening through various steps to definite diagnosis. The number of cases at each step was used for cost calculation. At first step, 70.8% of 800,000 women underwent FTS with NIPS (nearly 30% had no screen; including some cases with DS), consisting of 915 DS and 565,485 non-DS pregnancies. Each group had branching for a further series of actions in case of positivity. For example, DS group consisted of high risk and low risk pregnancies. The low risk had no further test, though consisting of live birth DS and DS with spontaneous abortion. Nearly all high risk pregnancies accepted but some rejected NIPS; nearly all cases with +ve NIPS accepted amniocentesis in which nearly all cases had successful procedures and few had failed procedure or lab failure). Failure to detect DS could occur at any cascade; and finally not all detected DS accepted intentional abortion. Likewise, of non-DS group, false positive result could occur at any cascade, though it should not (lab error, specimen switching); intentional abortion could also occur though very rare

Back to article page