Is it cost effective to screen women for syphilis twice during pregnancy?

The UK National Screening Committee (UK NSC) asked Aquarius to assess the costs and benefits of two different approaches to antenatal screening for syphilis.

We compared the current strategy – screening in the first trimester only – with an alternative strategy – screening in the first trimester and a repeat screen later in pregnancy.  The results of our cost-effectiveness analysis were recently published in BMJ Open and are now available online.

Syphilis is a treatable sexually transmitted infection (STI) which can be passed from mother to foetus during pregnancy resulting in congenital syphilis. Syphilis infection also increases the risk of adverse pregnancy outcomes such as stillbirth and pre-term delivery. Most cases of congenital syphilis and adverse pregnancy outcomes can be avoided if the infection is diagnosed and correctly treated during pregnancy.

In the UK, pregnant women are offered screening for syphilis, HIV and hepatitis at their first antenatal appointment, typically at or before 12 weeks gestation. Despite the very high coverage of these routine screens plus repeat screening in some higher risk women, a handful of congenital syphilis cases still occur each year, either in women who miss screening or in women who become infected with syphilis after their antenatal screen. For this reason, the UK NSC wanted to assess the cost effectiveness of offering a repeat screen to all pregnant women later in pregnancy.

We worked closely with a small group of experts develop a decision tree and model inputs to compare the single and repeat screening strategies. The model accounted for the sensitivity and specificity of the syphilis assay, the small number of women who do not attend antenatal care until their third trimester (thereby missing the opportunity for repeat screening) and the costs associated with screening, delivery and antenatal care for all women delivering in the UK in one year.

We found that repeat screening would prevent 5.5 cases of congenital syphilis each year but at cost of £1.8 million per case avoided. When a lifetime horizon was considered, the incremental cost-effectiveness ratio (ICER) for the repeat screening strategy was £120,494 per QALY gained – well above the £20k-30k cost per QALY threshold that NICE uses to assess interventions.

The paper concludes that in the UK setting, where prevalence of syphilis is very low, repeat screening for syphilis in pregnancy would not be a cost-effective strategy and alternative strategies should be sought to prevent congenital syphilis. This is the first published study from outside the US to compare these two screening strategies. The results will be used to inform national screening policy and are relevant to countries with similar syphilis prevalence and healthcare costs. 

This is one of many health economic evaluations that Aquarius has developed – to find out more about our work please visit https://aquariusph.com/services/economic-evaluation/ or email us at info@aquariusph.com