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Developments in the screening for Chlamydia trachomatis: a review.
Obstetrics and Gynecologic Clinics of North America 2003;30:637-658.
Kohl KS, Markowitz LE, Koumans EH.
Abstract
Many studies have evaluated selective screening criteria for women in various
settings. Most have concluded and all guidelines recommend that all women
aged < 25 be screened yearly for C. trachomatis infection. Behavioral
criteria, such as the number of sex partners, new or more than one sex partners,
and previous infection, also can serve as criteria for screening women aged > 25.
Because re-infection rates are high and occur within a few months, complications
may be reduced further if partners are treated and women rescreened 4 to
6 months after initial infection. Revised recommendations for C. trachomatis
screening programs have stated that more frequent screening may be considered
among women < 20 and those with recent infection. Screening in nontraditional
settings and careful evaluation of local prevalence and risk factor information
should be encouraged. Private providers and emergency room providers should
discuss screening recommendations and adopt a C. trachomatis screening policy
for the population they serve. The HEDIS measure should serve to encourage
at least annual screening of 15- to 25-year-old sexually active females through
providers linked to managed care organizations. In general, high yields (ie,
percentage of tests that are positive) in nontraditional settings and enhanced
feasibility and acceptability of urine-based tests may encourage further
innovative approaches to reach and screen populations at risk. Several issues
remain to be addressed to increase the effectiveness of screening efforts.
If more sensitive amplification tests are used widely, more infected persons
will be identified and treated, and transmission patterns may change, particularly
if partner treatment also occurs. Current screening criteria should continue
to be re-evaluated. An important issue that affects testing methods includes
the possible need for confirmation testing when using NAATs if the prevalence
of C. trachomatis is less than 2%. If the sensitivity of an NAAT is 85% and
specificity is 99%, in a hypothetical population of 10,000 with a prevalence
of 2%, the positive predictive value is 170/268 (63%). A second important
issue affecting testing methods and feasibility of using NAATs for screening
large numbers of individuals is the pooling of urine specimens, which has
been evaluated in several studies and found to be very effective for reducing
costs. A research issue for pooling is the determination of the most cost-effective
prevalence levels for pooling. An additional research question is in which
populations should a NAAT be used for detection of C. trachomatis and N.
gonorrhoeae. There are no recommendations for the routine screening of men
because of the paucity of data showing that this strategy can reduce sequelae.
The CDC is conducting a multisite study to examine the feasibility, acceptability,
and usefulness of screening of asymptomatic men. There are a few studies
have determining cost-effective prevalence threshold levels, particularly
with NAATs. A recently developed decision analysis model by CDC designed
to maximize the effectiveness of screening strategies for C. trachomatis
infections may be useful for decision makers. It is intended to serve as
an easy and flexible tool to determine cost effectiveness at a local level
and takes into account positivity rates and test performance characteristics
(SOCRATES). It is unclear if recurrent infection is caused by true re-infection
by the same or a different partner or recurrence of initial infection. Recurrence
may be caused by persistence of C. trachomatis or antibiotic resistance.
This distinction is of scientific interest because the appropriate intervention
differs (eg, identification of risk factors for the former and microbiologic
investigations for the latter). Effective partner management and retesting
are critical to reducing sequelae of C. trachomatis infection. Screening
for C. trachomatis infection remains an essential component of C. trachomatis
control. It is cost effective, most infections are asymptomatic, and symptom-based
health care seeking and testing identify few of those infected. The likelihood
that opportunities for screening are missed is high particularly in non-STD
clinic settings. Local studies using NAATs to determine C. trachomatis prevalence
and risk factors are helpful to health care providers so they can make evidence-based
decisions on who to screen. The use of nontraditional, non-clinic-based test
settings should be explored further. We have focused on summarizing the medical
evidence regarding recommendations for screening for C. trachomatis. High-risk
populations for C. trachomatis infection may overlap with populations for
other STDs, and comprehensive STD prevention programs that involve a range
of STD service providers are needed to successfully reduce the STD-related
health burden in the population.