Prioritizing Congenital Syphilis Control in South China: A Decision Analytic Model to Inform Policy Implementation

Abstract

Nicholas Tan and colleagues use a decision analytic model to quantify the impact of the ten-year national syphilis control plan in China and conclude that earlier and more extensive screening are also necessary for reaching policy goals.

Abstract

Background

Syphilis is a major public health problem in many regions of China, with increases in congenital syphilis (CS) cases causing concern. The Chinese Ministry of Health recently announced a comprehensive 10-y national syphilis control plan focusing on averting CS. The decision analytic model presented here quantifies the impact of the planned strategies to determine whether they are likely to meet the goals laid out in the control plan.

Methods and Findings

Our model incorporated data on age-stratified fertility, female adult syphilis cases, and empirical syphilis transmission rates to estimate the number of CS cases associated with prenatal syphilis infection on a yearly basis. Guangdong Province was the focus of this analysis because of the availability of high-quality demographic and public health data. Each model outcome was simulated 1,000 times to incorporate uncertainty in model inputs. The model was validated using data from a CS intervention program among 477,656 women in China. Sensitivity analyses were performed to identify which variables are likely to be most influential in achieving Chinese and international policy goals. Increasing prenatal screening coverage was the single most effective strategy for reducing CS cases. An incremental increase in prenatal screening from the base case of 57% coverage to 95% coverage was associated with 106 (95% CI: 101, 111) CS cases averted per 100,000 live births (58% decrease). The policy strategies laid out in the national plan led to an outcome that fell short of the target, while a four-pronged comprehensive syphilis control strategy consisting of increased prenatal screening coverage, increased treatment completion, earlier prenatal screening, and improved syphilis test characteristics was associated with 157 (95% CI: 154, 160) CS cases averted per 100,000 live births (85% decrease).

Conclusions

The Chinese national plan provides a strong foundation for syphilis control, but more comprehensive measures that include earlier and more extensive screening are necessary for reaching policy goals.

Please see later in the article for the Editors' Summary

Editors' Summary

Background

Every year, 1.5 million pregnant women are infected with syphilis, a bacterial infection that is usually transmitted during sexual contact but that can also pass from a mother to her unborn child. In many of these women, the disease is detected through routine antenatal testing and is successfully treated with penicillin. But among those women who are not treated, about half experience adverse outcomes—the death of their baby during early or late pregnancy (fetal death and stillbirth, respectively) or soon after birth (neonatal death), or the birth of an infected baby. Babies born with syphilis (congenital syphilis) often fail to thrive and can develop problems such as blindness, deafness, and seizures if not treated. In 2008, syphilis in pregnancy contributed to 305,000 fetal deaths, stillbirths, and neonatal deaths, and 215,000 babies were affected by other adverse consequences of congenital syphilis. Yet congenital syphilis is simple and cheap to eliminate—a few injections of penicillin can clear the infection in a pregnant woman, and screening all pregnant women for syphilis is feasible even in low-resource settings.

Why Was This Study Done?

Congenital syphilis has recently reemerged in China. In the 1990s, there were very few cases of congenital syphilis in China, but by 2009, the reported incidence of congenital syphilis had risen to 139 cases per 100,000 live births. In 2010 the Chinese Ministry of Health announced a ten-year National Syphilis Prevention and Control Plan (NSCP) that, in line with World Health Organization (WHO) recommendations, aims to reduce the incidence of congenital syphilis to fewer than 30 cases per 100,000 live births by 2015 and to fewer than 15 cases per 100,000 live births by 2020. China's strategy for achieving these targets includes increasing prenatal syphilis screening coverage to 80% in urban areas and 60% in rural areas, increasing treatment rates among infected women to 90% in urban areas and 70% in rural areas, and increasing syphilis awareness among adults. But will this strategy be sufficient? Here, the researchers develop a mathematical model to quantify the likely impact of the NSCP's strategy on the incidence of congenital syphilis in southern China.

What Did the Researchers Do and Find?

The researchers developed a decision analytic model in which women move through a sequence of health states from uninfected, through infection and pregnancy, and to the development of congenital syphilis, and fed data collected in Guangdong Province between 2005 and 2008 on women's fertility, female syphilis cases, and syphilis transmission rates into the model. The researchers checked that their model provided estimates of the incidence of congenital syphilis that matched the reported incidence for Guangdong Province (internal validation) and the reported incidence in a congenital syphilis intervention program in Shenzhen, Guangdong (external validation). They then used their model to identify which parts of the NSCP strategy are likely to have the greatest effect on the incidence of congenital syphilis. Increasing prenatal screening coverage was the single most effective strategy for the reduction of congenital syphilis, but neither this strategy alone nor implementation of the whole NPSC strategy achieved the plan's target outcomes. By contrast, a four-pronged approach (95% coverage of prenatal screening, 75% of screening during the first two-thirds of pregnancy, 95% treatment completion, and having an accurate screening test) reduced the estimated incidence of congenital syphilis cases to 27 per 100,000 live births.

What Do These Findings Mean?

These findings suggest that although the NSCP is a strong foundation for control of congenital syphilis in China, more comprehensive measures will be needed to reach the plan's policy goals. In particular, the findings suggest that earlier and more extensive screening will be needed to reduce the incidence of congenital syphilis to below 30 cases per 100,000 live births, WHO's benchmark for congenital syphilis control. The accuracy of these findings is limited by the assumptions included in the model and by the data fed into it. Moreover, because the data included in the model came from Guangdong Province, these findings may not apply elsewhere in China or in other countries. Nevertheless, this study illustrates the importance of using multi-pronged approaches to address the complex problem of congenital syphilis control and identifies some strategies that are likely to improve the control of this important public health problem.

Additional Information

Please access these websites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.1001375.

• The World Health Organization provides information on sexually transmitted infections, including details of its strategy for the global elimination of congenital syphilis, the investment case for the elimination of mother-to-child transmission of syphilis, and regional updates on progress towards elimination (some information is available in several languages)

• The US Centers for Disease Control and Prevention has a fact sheet on syphilis

• The UK National Health Service Choices website also has a page on syphilis

• MedlinePlus provides information on congenital syphilis and links to additional syphilis resources (in English and Spanish)

• Haiti: Congenital Syphilis on the Way Out is a YouTube video describing the introduction of rapid diagnostic tests for syphilis in remote parts of Haiti