Results were expressed as an average cost-effectiveness ratio, as an incremental cost effectiveness ratio to screening based solely on maternal age and as an incremental cost effectiveness to the 'Double test'.
Under the base case assumptions the authors found that the addition of uE3 to the California screening programme would detect an additional 44 cases of Down Syndrome at an incremental cost effectiveness ratio of $119,100 compared with the 'Double Test' (average cost effectiveness ratio of $147,400) and would detect an additional 192 cases at an incremental cost effectiveness ratio of $68,200 in comparison with screening based solely on maternal age (average cost effectiveness ratio of $187,300).
The sensitive parameters were found to be the incremental cost and sensitivity of oestriol (e.g. when the incremental cost of oestriol is $16 and the incremental sensitivity of uE3 is 1% the incremental cost-effectiveness drops to $1,187,700 per case detected). Varying the amniocentesis rate had a marked effect on the incremental cost effectiveness ratio of uE3 (eg the incremental cost effectiveness ratio is $231,300 at a 50 per cent amniocentesis rate).