Objective
We sought to determine the clinical utility and cost of repeating syphilis testing in the third trimester of pregnancy in a high-risk urban population.
Study Design
A retrospective cohort analysis was performed for patients delivering from January 1993 through December 2009 with at least 1 venereal disease research laboratory (VDRL) test sent during pregnancy. Chart review was performed for patients with confirmed syphilis to determine the temporal relationship of syphilis diagnosis to the pregnancy. For patients who seroconverted during pregnancy (no antecedent history or treatment for syphilis), newborn charts were reviewed. The costs of treating seropositive neonates and the costs of implementing additional third-trimester syphilis screening were then compared.
Results
In the 17-year cohort, 58,569 deliveries were available for analysis. In all, 113 new cases of syphilis occurred (192.9/100,000 deliveries). There were 17 detected seroconversions; 10 were not rescreened in the third trimester and tested positive at delivery. These 10 patients may have benefitted from implementing uniform VDRL testing at 28-32 weeks’ gestation. All newborns were asymptomatic with a negative workup and received empiric penicillin therapy. Based on 2011 hospital charges, the cost of evaluating and treating a neonate for syphilis is $11,079. Implementing an additional VDRL screen at 28-32 weeks’ gestation for each pregnant patient during the 17 years studied would cost $1,991,346. An 18-fold increase in syphilis prevalence (3500/100,000 [3.5%] deliveries) would be required for the cost of implementation of universal early third-trimester screening to be equal to the potential health care charges saved by detecting maternal seroconversion and obviating the need for neonatal therapy.
Conclusion
In this high-risk population, additional syphilis screening in the third trimester is costly and is not clinically helpful in detecting maternal seroconversion.
Syphilis rates in US women peaked in the 1990s but have been decreasing since 2008. Paralleling this decline, rates of congenital syphilis have decreased in recent years from the Centers for Disease Control and Prevention (CDC) quotes of 10.5 cases/100,000 live births in 2008 to 8.5 cases/100,000 live births in 2011. As reassuring as these trends appear, rates of syphilis in subgroups of the US population have remained relatively high, particularly in urban areas and the South.
In Cuyahoga County, Ohio, syphilis rates have remained significantly higher than national numbers at 9.8 cases/100,000 population in contrast to the national rate of 4.5 cases/100,000 (2012). The city of Cleveland is one of the top 4 highest syphilis prevalence areas in Ohio with rates in 2012 of 24.4 cases/100,000 population. New cases in men comprise the majority of these numbers. Statistics have not been readily available for pregnant women in this area.
It is well recognized that maternal syphilis infection in pregnancy can have far-reaching consequences for maternal and fetal health. The American Congress of Obstetricians and Gynecologists and the CDC recommend syphilis screening for pregnant women at the initial prenatal visit as well as at delivery. For women who have additional risk factors, defined as living in a high-prevalence geographic area, drug use, high-risk sexual behaviors, incarceration, and/or lack of health insurance, an additional syphilis screen at 28-32 weeks’ gestation is advised. The rationale for this additional test is to detect potential seroconversions in time for administration of adequate antimicrobial treatment prior to delivery (>30 days) so as to prevent neonatal syphilis infection and avoid prolonged neonatal hospital admission for treatment.
At MetroHealth Medical Center, a tertiary-care hospital in Northeast Ohio serving the Cleveland area, the pregnant patient population meets many of the high-risk criteria listed above. Based on geographic area alone, all pregnant women at our institution would be considered high risk. Typical screening practice is to obtain a venereal disease research laboratory (VDRL) test at initial visit and at delivery. Patients are not uniformly rescreened in the early third trimester based on geographic risk factor alone. However, if an additional risk factor exists, the patient is typically rescreened at 28-32 weeks’ gestation. Given the paucity of data regarding rates of new syphilis cases and seroconversion rates in pregnant women, it is unclear if our geographically “high-risk” population would benefit from a universal early third-trimester screen and, in turn, if the cost of this practice would be outweighed by the costs saved with congenital syphilis prevention. This question was addressed in 2006 by Edwards et al, who calculated syphilis rates over the course of 1 year among a cohort of pregnant patients. In that population, there were no cases of syphilis observed and the conclusion was that additional syphilis screening was not warranted as disease rates were so low. We believe that the incidence of syphilis in our population has been much higher than in that cohort. Also, because national rates have fluctuated quite dramatically in the last 2 decades and are likely to continue to vary year-to-year, it is important to consider more than a single year in any analysis.
The goal of this study was to determine the incidence of new syphilis cases and syphilis seroconversion rates in a high-risk pregnant population over a 17-year time period. Based on these findings, we aimed to find if adding an additional, universal third-trimester syphilis screening test would be clinically beneficial in the early detection of maternal seroconversion and, in turn, the prevention of congenital syphilis cases.
Materials and Methods
A retrospective, institutional review board–approved, cohort analysis was performed for all patients delivering at our tertiary-care, urban hospital, from January 1993 through December 2009, who had at least 1 VDRL test done during pregnancy. All deliveries were identified using our computer-based electronic perinatal database. Any associated VDRL and fluorescent treponemal antibody absorption test (FTA) results for these patients were obtained from our laboratory database. To eliminate false-positive VDRL values, patients with at least 1 positive FTA during the index pregnancy were considered true positives and these charts were flagged for further review. Individual chart review was then performed for all patients with a positive VDRL and FTA result to determine if each patient had a diagnosis of syphilis preceding pregnancy, a new diagnosis of syphilis at initial VDRL screen, or evidence of seroconversion (ie, a negative VDRL result that became positive later in gestation). For patients who seroconverted during pregnancy and had no antecedent history of or treatment for syphilis, review of each newborn chart was performed, looking specifically at clinical course, diagnosis, and treatment of congenital syphilis.
A comparison of the cost for additional syphilis testing at 28-32 weeks’ gestation vs the cost of empiric treatment of the neonates born to mothers with missed syphilis seroconversions was then performed using our hospital’s net charges.
Results
In this 17-year cohort, there were 60,225 live births at our institution. A total of 58,569 deliveries were available in our database for analysis. Of these, 57,642 deliveries had at least 1 VDRL test available for analysis (98.4%). The total number of qualitative VDRL, quantitative VDRL, and FTA tests was 126,648; of this total, 122,408 were qualitative VDRL tests ( Figure 1 ). The average number of VDRL tests sent per pregnancy was 2.1.
In all, 113 new cases of syphilis occurred during the 17-year period (192.9/100,000 deliveries). The annual incidence of new syphilis cases varied dramatically over the 17 years studied, from 28.8/100,000 live births in 2007 to 703.7/100,000 in 1994 ( Table ). Among these new diagnoses, there were 17 detected seroconversions. Four of these 17 patients were retested during the third trimester and were therefore diagnosed >30 days before delivery, allowing for sufficient antenatal treatment and eliminating the need for newborn treatment. An additional 3 patients retested during the third trimester were test negative but had a subsequent positive VDRL result on admission for delivery. These were not considered missed diagnoses as these patients had received an early third-trimester rescreen, but did not benefit from the additional testing. Ten patients were not rescreened in the third trimester and tested positive at delivery. These 10 patients could have potentially benefitted by implementing uniform maternal VDRL testing at 28-32 weeks’ gestation (if infection occurred prior to this time). All 10 newborns were asymptomatic; had a negative lumbar puncture, positive syphilis titers, and negative radiographic surveys; and received a 10-day hospital course of empiric intravenous penicillin therapy. No infants had unexpected sequela following treatment.
| Year | Deliveries available for analysis | New syphilis cases a | Rate/100,000 deliveries a | Seroconversions |
|---|---|---|---|---|
| 1993 | 4101 | 28 | 682.8 | 7 |
| 1994 | 3837 | 27 | 703.7 | 3 |
| 1995 | 3644 | 16 | 439.0 | 3 |
| 1996 | 3697 | 11 | 297.5 | 0 |
| 1997 | 3544 | 6 | 169.3 | 0 |
| 1998 | 3331 | 3 | 90 | 0 |
| 1999 | 3306 | 2 | 60.5 | 0 |
| 2000 | 3568 | 2 | 56.0 | 1 |
| 2001 | 3308 | 2 | 60.5 | 2 |
| 2002 | 3250 | 1 | 30.8 | 0 |
| 2003 | 3313 | 3 | 90.6 | 0 |
| 2004 | 3247 | 3 | 92.4 | 1 |
| 2005 | 3322 | 2 | 60.2 | 0 |
| 2006 | 3372 | 3 | 88.97 | 0 |
| 2007 | 3478 | 1 | 28.8 | 0 |
| 2008 | 3398 | 1 | 29.4 | 0 |
| 2009 | 2853 | 2 | 70.1 | 0 |
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