Construcción del prototipo

7.4.2.1 Cost-effectiveness of lowering failure to screen rates

An alternative to a universal strategy is a selective strategy with a lower failure to screen rate. Under the assumption that reducing the failure to screen rate in a selective programme does not justify extra costs, it is possible to calculate the additional cost per additional choice offered upon changing from a selective strategy w ith a higher failure to screen rate to one with a lower failure to screen rate (table 7.19). I f these ICERs are compared to those for changing from selective to universal screening, it is evident that it is always more cost-effective to reduce the failure to screen rate in a selective programme than to switch to a universal strategy.

Table 7.19 Incremental cost-effectiveness o f moving from a higher to a lower

failure to screen rate in selective programmes, for choices and affected live birth prevented

Prevalence ICERs ( £ ’s) for m oving from a higher to a low er selectiv e failure to screen rate C hoice ICER A ffected liv e birth prevented ICER

High 2945 24113

M edium 5644 51693

Low 6533 504 5 6

Apart from selective failure to screen rates all other parameters held at baseline lev els (table 4.1, 4 .2 , pages 9 1 -9 4 ). Assumption: reduction in selective failure to screen rate does not incur extra costs.

The reason for this is that although costs increase if more ethnic minority women are screened, more women with affected fetuses are offered choice in the same proportion.

7.4.2.2 Selective screening strategy based on ethnicity without regard to MCH The selective antenatal screening strategy analysed in this study assumes that all women with low MCH undergo Hb-pathy carrier testing (for ease o f presentation this strategy is referred to as standard selective strategy in the subsequent section). An alternative selective strategy would be to screen on the basis o f ethnic status alone and regardless o f MCH result. Compared to this selective strategy based on ethnicity without regard to MCH, the standard selective strategy offers choice to more women with affected fetuses in two ways. Firstly, it identifies all women with thalassaemia traits, whether ethnic minorities or not, failing only at the 0.5% presumed universal

failure to screen rate. Secondly, among those with low MCH the standard strategy will identify all but 0.5% of sickle carriers, while the alternative strategy would miss 5.5%, under baseline assumptions. The advantage o f carrier testing o f those w ith low MCH regardless o f ethnic status is not so much that it offers choice to N orth European women with fetuses affected by thalassaemias. Instead, the advantage is that it offers choice to those ethnic minority women with affected fetuses, whether with sickle cell disease or thalassaemias, who might have been missed by a selective programme based on ethnic status alone.

The precise cost-effectiveness o f the standard selective strategy over the alternative one depends on the differential failure to screen rate, and also on the presumed

prevalence o f iron deficiency in the antenatal population (table 7.20). On baseline

assumptions o f 10% iron deficiency, the alternative strategy costs between £3,800 and £5,200 less than the standard selective strategy, per 10,000 pregnancies. The choice ICERs for changing from selective screening based on ethnicity without regard to MCH to the standard selective strategy is less than £100,000 in 53 districts. This should be compared to 14 districts in which the universal versus standard selective ICERs were less than £100,000.

Although the absolute cost of the standard selective strategy, compared to selective screening based on ethnicity without regard to MCH, is relatively low, and it is a cost- effective option in many districts, table 7.20 also indicates that ICERs are increasing from the high to the low prevalence district and fi-om lower to higher levels o f iron deficiency. The economic case for the standard selective strategy to be implemented everywhere is therefore not entirely compelling. However, a full analysis requires a model that includes alternative management o f low MCH in North European women. This was beyond the scope o f the this study.

Table 7.20 Incremental cost-effectiveness for choice offered o f moving from a programme of selective screening based on ethnicity without regard to M CH to the standard selective strategy which allows for haemoglobinopathy carrier testing of all women with low MCH, assuming different levels o f iron deficiency

Prevalence C hoice ICERs ( £ ’s) for moving from selective screening based on ethnicity w ithout regard to MCH to standard selective screening, under varying iron d eficien cy lev els

Iron deficiency 5% Iron deficien cy 10% Iron d eficien cy 30%

High 6057 7 420 12049

M edium 18795 26875 6 0 0 1 9 Low 127834 2 00188 4 8 9 5 5 9

Apart from vaiyin g levels o f iron deficien cy all other parameters held at baseline levels (table 4 .1 , 4.2 , pages 91- 94).

7.4.2.3 No antenatal screening

In this context ‘no screening’ is taken to mean no carrier testing, regardless o f MCH.

Table 7.21 shows that the ICERs for changing from no screening to selective

screening are lower than the ICERs for changing from a selective to a universal strategy. They are also substantially lower than the lowest assumed acceptable ICER values (chapter 6), suggesting a strong economic case for selective screening compared to a no screening policy.

Table 7.21 Incremental cost-effectiveness of moving from no screening to

selective screening, based on choices offered and affected live births prevented

Prevalence ICERs ( £ ’s) for m oving from no screening to selective screening Choice ICER A ffected live birth prevented ICER

High 3134 2 4 7 4 6

Medium 6801 373 6 7

Low 17083 59108

M odel predictions under baseline assumptions (table 4.1, 4.2, pages 91-94).

However, this conclusion could be overturned if ethnic ascertainment and provision o f pre-test information are included in the costs o f selective screening. For every minute spent on ethnic ascertainment and pre-test information, about £3,800 per

10,000 antenatal population is added to the cost o f screening. This should be compared to the £9,400 cost o f the standard selective strategy in the low prevalence district, or £5,000 for the selective screening strategy based on ethnicity without regard to MCH. The result is that, as more time is spent on ethnic ascertainment and pre-test information, selective screening becomes less cost-effective in areas o f lower

Table 7.22 Number of districts (maximum 170) that would adopt a no screening policy in preference to either the standard selective strategy or selective

screening based on ethnicity without regard to MCH, in relation to time spent for ethnic ascertainment and/or pre test information

C hoice ICER Number o f districts that would adopt no screening in preference to selectiv e screen in g in relation to time spent each for ethnic ascertainment and/or pre-test inform ation

Standard selective screening S elective screening based on ethnicity regardless o f M C H