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Review: Because
most infections with C. trachomatis are asymptomatic,
screening for C. trachomatis infection is essential and
cost-effective.
Developments in the screening for Chlamydia
trachomatis: a review.
Kohl KS, Markowitz LE, Koumans EH.
Obstetrics and Gynecological Clinics of North America
2003;30:637-658.
Summary:
Question
What are the risk factors for C. trachomatis infection, the
effectiveness of screening criteria, the newer tests and their uses, and
recent changes in guidelines related to C. trachomatis tests and
screening?
Data sources
A search of Medline from 1996 through April, 2003, was performed using the
terms "chlamydia" and "screening". Articles with
earlier dates were included if they provided the most recently available
or comprehensive treatment of the topic. References in published articles
were reviewed. Abstracts presented at the International Society for
Sexually Transmitted Diseases Research meetings (1999 and 2001) and at the
National STD Prevention Conferences (1998, 2000, and 2002) were reviewed.
Articles were screened to assess whether
they discussed evaluation of risk factors and screening, or
cost-effectiveness for women or men, evaluation of test frequency and
repeat testing for women, or screening and treatment of pregnant women.
Recent guidelines from various United States health agencies were
reviewed.
Main Results
Useful selective screening criteria should have a high sensitivity, a high
positive predictive value, and screen the smallest proportion of women
consistent with prior objectives. Performance of screening criteria
depends on the prevalence of C. trachomatis in the community and on
demographics and risk factors among patients. It has been difficult to
identify screening criteria that select most infected women without also
increasing the proportion of women tested. Using different criteria, the
proportion of women required to be screened in order to identify a
proportion of women infected has varied widely. For example, in one study,
using the criterion of all sexually active women, 40% of all women were
screened and 24% of infected women were identified. In another study,
using all women less than 25 years old as the testing criterion, 88% of
women were screened to identify 95% of infected women. Almost all studies
that evaluated sensitivity and predictive value of screening criteria
concluded that age (<27, <25, or <22) was the best criterion for C.
trachomatis screening. Previous infection has also been a useful
screening criterion.
One study found that universal screening
using urine PCR was cost saving if the prevalence exceeded 3.9%. Other
studies found that screening based on age (<25 or <30 years) was
more cost effective than universal screening. Different studies have found
varying break-even prevalence levels for screening from 1.1% to more than
10%. Amplification tests, particularly urine-based tests, were cost-saving
over nonamplification tests at more than 3.2% to >6% prevalence.
Guidelines recommend screening of all
sexually active women < 25 years old, high-risk women (sexually
active women with multiple or a new sex partner and inconsistent use of a
barrier method) in areas in which prevalence is >10%, women with
clinical signs of infection, pregnant women at the initial prenatal visit
and the third trimester for women who initially were positive, and men at
high risk for infection and in high prevalence settings.
Authors' Conclusions
Most studies have concluded, and all
guidelines recommend that all women aged <25 years and those
women aged >25 years who meet behavioral criteria, be screened yearly
for C. trachomatis infection. If more sensitive amplification tests
(NAAT) are widely used, more infected persons will be identified and
treated. Confirmation testing when using NAAT should be performed if the
prevalence of C. trachomatis is less than 2%. One issue affecting
the feasibility of using NAAT for screening large numbers of individuals
is the pooling of urine specimens, which has been found to be very
effective for reducing costs.
Source of funding:
Not given
For correspondence:
Emilia H. Koumans, Division of STD Prevention, National Center for HIV,
STD, and TB Prevention, Centers for Disease Control and Prevention, 1600
Clifton Road NE, Atlanta, GA 30333. E-mail address: ekoumans@cdc.gov
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