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Congenital Syphilis Surveillance and Newborn Evaluation in a Low-Incidence State
Dawn L. Martin, MD, MPH;
Jolene R. Bertrand, BS;
Catherine P. McKegney, MD;
Linda R. Thompson, MD;
Edward A. Belongia, MD;
Wendy A. Mills, MPH
Arch Pediatr Adolesc Med. 2001;155:140-144.
ABSTRACT
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Objectives To evaluate congenital syphilis surveillance in Minnesota, to assess
the evaluation and management of newborns at risk for congenital syphilis,
and to assess prenatal syphilis screening.
Design Case ascertainment and medical record review.
Setting The 7-county Minneapolis–St Paul metropolitan area.
Patients Newborns at risk for congenital syphilis during a 3-year period (1992-1994).
Main Outcome Measures The completeness of congenital syphilis case ascertainment, maternal
demographic data, maternal syphilis management, newborn evaluation for and
management of congenital syphilis, and hospital syphilis screening practices
at delivery.
Results Eighty mother-infant pairs who were at risk for congenital syphilis
were identified from 3 sources. Using the Centers for Disease Control and
Prevention's congenital syphilis case definition, 36 infants (45%) were classified
as probable cases, 42 (53%) were classified as noncases, and 2 (3%) were syphilitic
stillbirths. Forty-seven women (59%) had syphilis serologic tests performed
in the third trimester; only 37 (46%) had syphilis screening at delivery.
Conditions of the mothers of 8 probable cases (22%) were diagnosed at delivery.
Most probable cases (86%) were evaluated; only 56% were evaluated adequately.
Twenty-five probable cases (69%) were treated. Most hospitals did not have
formal policies for syphilis screening at delivery. The Minnesota Department
of Health's congenital syphilis registry lacked sensitivity (39%) as a case
ascertainment method.
Conclusions Clinicians should adhere to standardized protocols in the evaluation
and management of at-risk newborns. Vigilant screening prenatally and at delivery
and adequate follow-up are critical to reduce congenital syphilis. Improved
surveillance data and resources are needed for the identification and follow-up
of newborns at risk for congenital syphilis.
INTRODUCTION
DESPITE available and effective treatment for syphilis, congenital syphilis
remains a public health and clinical challenge. After 2 decades of declining
rates of primary and secondary syphilis, the incidence of early syphilis and
congenital syphilis increased markedly in the 1980s and early 1990s.1, 2 Although some of the reported increase
in congenital syphilis was attributable to the Centers for Disease Control
and Prevention's (CDC's) expansion of the surveillance case definition for
congenital syphilis in 1988,3 a true increase
is suggested by the epidemic of early syphilis in women of childbearing age.1, 2 Although the incidence of syphilis
in Minnesota is lower than the national rate, similar temporal trends have
occurred here, with higher rates observed in urban areas (Figure 1).4
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Early syphilis rates in Minnesota by area of residence, 1990-1997.
Rates were not available in 1990 for greater Minnesota and suburban areas.
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Although the syphilis epidemic has diminished during the past 5 years
and the national incidence rate (3.2 cases per 100 000 population) is
at an all-time low,5 syphilis remains a significant
endemic public health problem. Furthermore, periodic epidemics will continue
to occur until syphilis is eliminated.6
In a low-incidence state such as Minnesota, evaluation and management
of newborns at risk for congenital syphilis are particular challenges for
health care providers. The CDC surveillance definition, which was revised
in 1996, is highly sensitive and often includes asymptomatic infants.7, 8 Also, clinicians caring for newborns
often are unfamiliar with the complex protocols for evaluation and management
of congenital syphilis. In addition to the CDC's surveillance case definition
of congenital syphilis, several other published protocols9, 10, 11, 12, 13
define a clinical case of congenital syphilis and provide varied guidelines
for the evaluation and management of at-risk newborns.
We conducted a study to evaluate the completeness of Minnesota's congenital
syphilis surveillance system, to assess the evaluation and management of neonates
at risk for congenital syphilis, and to assess physicians' knowledge and practices
regarding prenatal screening for syphilis.14
METHODS
In Minnesota, health care practitioners and laboratories are required
to report syphilis cases to the Minnesota Department of Health (MDH). Infants
possibly at risk for congenital syphilis and born in the 7-county Minneapolis–St
Paul metropolitan area during 1992 through 1994 were identified from 3 sources:
(1) the MDH's congenital syphilis registry, (2) discharge records from hospitals
in the metropolitan area for infants younger than 2 years with an International Classification of Diseases, Ninth Revision (ICD-9)15 discharge diagnosis code consistent with congenital
syphilis during the study period, and (3) pregnant women who were diagnosed
as having syphilis and reported to the MDH in 1991 through 1994 and who had
delivered during 1992 through 1994. Eligible mother-infant pairs included
those in which the mother had a history of syphilis during pregnancy and/or
the newborn was diagnosed as having congenital syphilis during the study period.
This study was approved by the Human Subjects Review Committee at Hennepin
County Medical Center.
Hospital records for all mothers and newborns identified were reviewed
by one of us or a hospital infection control practitioner using a standardized
data abstraction form. Maternal demographic data, clinical information regarding
treatment of maternal syphilis, and data regarding the diagnosis, evaluation,
and management of the newborns were abstracted from medical records. Newborns
were classified using the CDC surveillance case definitions for syphilitic
stillbirths, probable syphilis cases, and confirmed cases of congenital syphilis.7, 16 A syphilitic stillbirth was defined
as a fetal death in which the mother had untreated or inadequately treated
syphilis at delivery of a fetus after a 20-week gestation or of a fetus weighing
more than 500 g. A probable case was defined as (1) an infant whose mother
had untreated or inadequately treated syphilis at delivery, regardless of
signs in the infant or child, or (2) an infant or child who has a reactive
treponemal test result for syphilis and any 1 of the following: evidence of
congenital syphilis on physical examination, any evidence of congenital syphilis
on radiographs of long bones, a reactive cerebrospinal fluid (CSF) VDRL test
result, an elevated CSF cell count or protein level (without cause), or a
reactive fluorescent treponemal antibody absorbed 19S IgM antibody test result
or IgM enzyme-linked immunosorbent assay. A confirmed case required laboratory-confirmed
identification of spirochetes.7
To document local hospitals' obstetrical screening practices for syphilis
at delivery, a standardized questionnaire was used to conduct a telephone
survey of obstetrical nursing supervisors at all 13 hospitals in the Minneapolis–St
Paul metropolitan area where mother-infant pairs were identified.
Univariate analyses were performed using standard microcomputer software
to calculate rate ratios (RRs) and 95% confidence intervals (CIs).17 Differences between means of continuous variables
were compared using the nonparametric Kruskal-Wallis test. P<.05 was considered statistically significant. The "capture-recapture"
method outlined by McCarthy et al18 was used
to estimate the completeness of case ascertainment via methods used in the
study to identify probable cases of congenital syphilis and syphilitic stillbirths.
The capture-recapture method uses log-linear modeling to correct for underascertainment.
RESULTS
CASE ASCERTAINMENT
Eighty-one eligible mother-infant pairs were identified from the 3 case-finding
sources. One woman reported to the MDH as a syphilis case during pregnancy
had a medical record that contained no evidence of syphilis, and her newborn
did not have congenital syphilis; this case was excluded from the study. Sixteen
newborns were identified through the MDH congenital syphilis registry, 26
newborns were identified by ICD-9 hospital discharge
data, and 72 pregnant women with syphilis were identified by case reports
to the MDH. Some mother-infant pairs were identified through more than one
source.
MATERNAL DEMOGRAPHIC DATA
The demographic and clinical characteristics of the 80 mothers are presented
in Table 1. The mothers ranged
in age from 16 to 40 years; they were predominantly racial and ethnic minorities,
and most were unmarried. Most mothers were insured by public assistance and
resided in urban areas. Compared with demographic data on pregnant women who
were delivered of newborns in the 7-county metropolitan area during the study
period, the mothers in this study were significantly more likely to be minorities
(RR, 4.9; 95% CI, 4.5-5.4; P<.001), to be unmarried
(RR, 5.0; 95% CI, 3.3-10.0; P<.001), and to reside
in an urban area (RR, 2.7; 95% CI, 2.4-3.0; P<.001).
Many (44%) of these women had coexisting sexually transmitted diseases. Human
immunodeficiency virus serologic test results were negative for 44 mothers
(55%) and positive for 1 (1%). Human immunodeficiency virus status was unknown
or not documented in the hospital birth record for 35 women (44%).
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Table 1. Characteristics of 80 Mothers Delivered of Newborns at Risk
for Congenital Syphilis, Twin Cities Metropolitan Area, 1992-1994
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NEWBORN EVALUATION AND MANAGEMENT
Newborns were classified based on an assessment of the adequacy of maternal
treatment for syphilis and clinical assessment of the newborn according to
CDC guidelines.7, 16 Of the 80
mother-infant pairs identified, 36 infants (45%) were classified as probable
syphilis cases, 42 (53%) were noncases, and 2 (3%) were syphilitic stillbirths.
None of the infants met the CDC definition of a confirmed case of congenital
syphilis.
Although the mean gestational age at birth of probable cases and noncases
did not differ significantly, the mean birth weight of the probable cases
(2995 g) was significantly less than that of noncases (3236 g) (P = .04).
Of the 36 probable cases, 34 (94%) were asymptomatic. Thirty-one (86%)
of the 36 probable cases received some clinical evaluation. Twenty (56%) of
the 36 cases were evaluated adequately (ie, complete clinical examination,
quantitative nontreponemal serologic tests, long bone radiographs, and CSF
evaluation), 11 cases (31%) were inadequately or partially evaluated, and
5 cases (14%) were not evaluated. Twenty-six probable cases (72%) had lumbar
punctures. Interpretation of CSF results was limited by missing information
(10 cases) or traumatic lumbar punctures (8 cases). Table 2 summarizes the evaluation and treatment of the newborns.
Two cases (6%) had clinical evidence of congenital syphilis, including 1 infant
who died with severe congenital syphilis (ie, hydrops, disseminated intravascular
coagulation, and neurosyphilis) hours after birth.
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Table 2. Newborns Who Received Evaluation and Treatment for Congenital
Syphilis, Twin Cities Metropolitan Area, 1992-1994*
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Twenty-five (69%) of the 36 probable cases were treated for congenital
syphilis. Twenty-two (88%) of these infants were treated with 10 to 14 days
of parenteral penicillin, 1 infant (4%) received 3 days of aqueous crystalline
penicillin G (this infant had a normal evaluation), and 2 infants (8%) received
several days of aqueous crystalline penicillin G and 1 dose of intramuscular
penicillin G benzathine. Both of these 2 infants had missing CSF data.
Ten probable cases were not treated (excluding the death); only 1 of
these newborns was evaluated for congenital syphilis. Eight of the 10 mothers
of these newborns had inadequate or unknown treatment, 1 had received nonpenicillin
therapy (erythromycin estolate), and 1 was not treated. Although the medical
records indicated the physician's awareness of maternal syphilis in 9 of 10
cases, only 2 of these mothers were screened for syphilis at delivery. None
of these 10 newborns had a discharge diagnosis that indicated congenital syphilis
or were reported to the MDH congenital syphilis registry. Follow-up data on
these newborns are unavailable.
Twenty-nine (69%) of 42 noncases had some evaluation for congenital
syphilis (eg, serologic testing, long bones, radiographs, and/or CSF evaluation),
and 4 noncases (10%) were treated for congenital syphilis.
MATERNAL PRENATAL CARE AND HOSPITAL SCREENING PRACTICES
Overall, 47 women (59%) had syphilis serologic testing performed in
the third trimester, and only 37 (46%) had syphilis screening at delivery.
Mothers (22%) of 8 of the probable cases were first diagnosed as having syphilis
at delivery. Five of the 8 mothers of probable cases diagnosed at delivery
had more than 1 prenatal visit. Mothers of noncases had more prenatal visits
(mean, 9) than mothers of probable cases (mean, 6) (P
= .003).
Only 2 (15%) of the 13 hospitals surveyed had a protocol for syphilis
screening at delivery. Of the 11 hospitals without a protocol, 9 (82%) reported
that screening at delivery was performed at the discretion of the admitting
physician. None of the 5 urban hospitals where most (77%) of the study cases
were identified had a formal policy for screening pregnant women for syphilis
at delivery. However, one of these hospitals routinely performed a cord blood
rapid plasma reagin test.
SENSITIVITY AND COMPLETENESS OF SURVEILLANCE METHODS
The sensitivity of each of the 3 potential congenital syphilis case
ascertainment methods was calculated based on the following: (1) the assumption
that all true cases of congenital syphilis were identified by at least 1 detection
method and (2) the fact that 118 332 live births occurred in the 7-county
metropolitan area during the study period. The CDC surveillance case definition
of a probable case of congenital syphilis or a syphilitic stillbirth was the
gold standard against which sensitivity was evaluated. The MDH congenital
syphilis registry identified 15 (39%) of 38 cases. The hospital discharge ICD-9 codes identified 21 cases (55%), and the MDH registry
of pregnant women with syphilis identified 33 cases (87%).
All 38 cases identified cumulatively by these 3 methods were included
in the reports to MDH of pregnant women with syphilis and/or the ICD-9 discharge diagnosis data; none of the 38 cases was identified
solely through the MDH congenital syphilis registry. Using the capture-recapture
method, the corrected number of presumptive cases of congenital syphilis and
syphilitic stillbirths ascertainable using both ICD-9
discharge diagnosis data and reports to MDH of pregnant women with syphilis
was estimated to be 43 (95% CI, 36-50). The percentage of these cases ascertained
by the aggregate data from these 2 methods was 88% (95% CI, 76%-100%), the
percentage of cases ascertained by the ICD-9 discharge
data alone was 49% (95% CI, 42%-58%), and the percentage ascertained solely
by data on pregnant women with syphilis was 77% (95% CI, 66%-91%).
COMMENT
Minnesota's experience with congenital syphilis highlights several issues.
First, the diagnostic evaluation and management of newborns at risk for congenital
syphilis are variable and lack consistent adherence to standard protocols.
The CDC's current surveillance definition of congenital syphilis is highly
sensitive and frequently may include asymptomatic infants. In addition, several
published protocols9, 10, 11, 12, 13
vary in their definitions of a clinical case of congenital syphilis and their
recommendations for evaluation of an infant at risk for congenital syphilis.
These case definitions rely heavily on documentation of maternal treatment
and maternal serologic status, although such data may not be readily available
to the clinician. Furthermore, the interpretation of laboratory results (particularly
CSF) used to evaluate these infants is hampered by poorly defined "normal"
results for CSF protein and white blood cell count and the frequent occurrence
of traumatic lumbar punctures.
This study demonstrates the varied approaches to the evaluation and
treatment of newborns at risk for congenital syphilis. Most noncases in this
study were evaluated but not treated. Other studies19
have reported more noncases receiving unnecessary treatment. More concerning,
however, is the varied evaluation and treatment of probable cases of congenital
syphilis in our study, with only slightly more than half receiving adequate
evaluation, according to guidelines of the CDC and the American Academy of
Pediatrics, and only two thirds of probable cases receiving treatment.9, 10 Most nontreated probable cases in
our study were not evaluated. It is of concern that none of these newborns
was discharged with a diagnosis of congenital syphilis or reported to the
MDH congenital syphilis registry, thereby limiting opportunities for follow-up
of these high-risk infants.
Consistent case definitions and protocols for the evaluation and treatment
of infants at risk for congenital syphilis are necessary. In 1996, Risser
and Hwang13 proposed modifying the protocol
for evaluation and treatment of asymptomatic infants born to treated mothers
whose infection status is uncertain to recommend omitting the CSF and long
bone analyses) and treating these infants with 1 injection of penicillin G
benzathine. However, it is difficult to definitively identify these infants,
and follow-up of such high-risk mothers and infants often is problematic.
Glasser20 expressed concerns about such an
approach and recommends closely adhering to the CDC guidelines for examining
and treating asymptomatic newborns at risk for congenital syphilis.
Aggressive screening and follow-up of pregnant women and women of childbearing
age are necessary to reduce the incidence of congenital syphilis. For populations
with a high prevalence of syphilis or for high-risk patients, the CDC recommends
serologic testing of pregnant women twice during the third trimester, at 28
weeks of gestation, and at delivery.9 Mothers
affected with syphilis in this study were demographically similar (eg, urban,
single, racial minorities, and insured by the public sector) to those described
elsewhere in the literature.21, 22, 23
Despite these known risk factors for syphilis, fewer than half of the mothers
in this study were screened for syphilis at delivery, and only 47 (59%) had
serologic testing performed in the third trimester. Also, it is of concern
that 22% of mothers of probable cases of congenital syphilis in this study
were first diagnosed as having syphilis at delivery. At least 5 of the 8 mothers
of probable cases diagnosed at delivery had more than 1 prenatal visit and
thus presumably represent missed opportunities for maternal syphilis screening
and treatment and the prevention of congenital syphilis.
Some states mandate screening for syphilis at delivery for all mothers;
however, Minnesota does not require such screening. Although Minnesota has
a low incidence of syphilis, endemic disease persists, with higher rates of
early syphilis in urban areas. None of the 5 urban hospitals where most mothers
in the study gave birth had a formal policy for screening pregnant women at
delivery. A prior study14 of physicians' practices
and opinions regarding prenatal screening for sexually transmitted diseases
found that of a sample of 172 family physicians and obstetricians practicing
in Minnesota, only 17 (10%) routinely obtained maternal blood samples for
serologic testing for syphilis at delivery. The location (ie, urban vs suburban
or rural) of physicians' clinics was not associated with their practices for
syphilis screening at delivery.
Improved surveillance is needed in Minnesota to monitor and accurately
describe the incidence and epidemiology of syphilis. The sensitivity of the
MDH congenital syphilis registry was estimated to be only 39% in this study,
suggesting that congenital syphilis may be underreported. A capture-recapture
analysis of the completeness of case ascertainment in this study suggests
that the case-finding methods used in the study identified 88% of the actual
number of probable cases of congenital syphilis or syphilitic stillbirths;
approximately 5 cases may have been undetected. The incompleteness of the
surveillance data may reflect clinicians' difficulty using congenital syphilis
case definitions and/or their lack of familiarity with mandated disease reporting.
Reports to the MDH regarding pregnant women with syphilis was the most
sensitive method of identifying probable cases of congenital syphilis, and
perhaps expanded prenatal follow-up of these women could alert clinicians
to at-risk newborns. However, this method fails to identify women first diagnosed
as having syphilis at delivery. These women frequently have high-risk behaviors,
such as chemical dependency, prostitution, history of incarceration, and moving
from state to state.
Congenital syphilis is a public health and clinical challenge. Vigilant
screening for syphilis (especially during pregnancy and delivery) is critical
to eliminate congenital syphilis. Clinician adherence to standardized protocols
for the evaluation and management of at-risk newborns is essential. However,
revised guidelines with consistent definitions and protocols may be needed
to assist physicians with this responsibility, particularly in low-incidence
areas, where clinicians infrequently face this clinical challenge. Also, public
health agencies responsible for disease surveillance may need new surveillance
systems and additional resources to assist in the identification and follow-up
of newborns at risk for congenital syphilis.
AUTHOR INFORMATION
Accepted for publication September 11, 2000.
We thank Kristine Moore, MD, for assisting in the development of this
study and Joni S. Geppert, MPH, RD, LN, for statistical support.
From the Departments of Pediatrics (Drs Martin and Thompson and Ms
Bertrand) and Family Practice (Dr McKegney), Hennepin County Medical Center,
the Minneapolis Medical Research Foundation (Ms Bertrand), and Minnesota Department
of Health (Ms Mills), Minneapolis, Minn; and Marshfield Medical Research Foundation,
Marshfield, Wis (Dr Belongia).
Corresponding author: Dawn L. Martin, MD, MPH, Department of Pediatrics,
MC 867B, Hennepin County Medical Center, 701 Park Ave, Minneapolis, MN 55415
(e-mail: dawn.martin{at}co.hennepin.mn.us).
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