Structured Abstract
Screening for Chlamydial Infection
Prepared by H. Dele Davies, MD, MSc, FRCPC, Assistant Professor of Microbiology,
of Infectious Diseases and of Pediatrics, University of Calgary, Alberta
These recommendations were finalized by the Task Force in October 1992
Contents
Objective
To make recommendations about screening for chlamydial infection (Chlamydia
trachomatis) among general, high risk and pregnant populations in Canada.
This updates a 1984 report.
Burden
of Suffering
Infection with Chlamydia trachomatis is the most common sexually transmitted
disease (STD) in North America, causing two to five times more infections
than Neisseria gonorrhea. In Canada, the incidence is 216 per 100,000
population. Screening in different female populations in Canada have shown
carrier rates of 1% to 25%, while 1% to 21% of all men may be asymptomatic
carriers. Risk factors for women include sexual activity during adolescence,
intercourse with 2 or more partners per year or new a partner in the preceding
year, low socioeconomic class, use of non barrier contraception, intermenstrual
bleeding, cervical friability and purulent discharge on examination.
Risk factors for men include younger age, multiple sexual partners in the
preceding year, and a history of gonorrhea in the past year.
Most infections in females (60-80%) are asymptomatic, but the
disease spectrum includes mucopurulent cervicitis (MPC), endometritis,
salpingitis, the urethral syndrome, proctitis, post-abortal pelvic sepsis
and perihepatitis. In numerous case-control and cohort studies chlamydial
infection has been associated with the long-term complications of pelvic
inflammatory disease (PID), infertility and ectopic pregnancy. In males,
the spectrum of disease due to C. trachomatis includes urethritis, epididymitis,
prostatitis and occasionally proctitis or proctocolitis via homosexual
transmission.
Options
Primary screening tests for adult women included speculum examination and
endocervical swab; cytologic testing using Giemsa or other methods; direct
fluorescent antibody (DFA) test using fluorescein-conjugated monoclonal
antibodies; and enzyme linked immuno-assays (EIA). Screening options for
men were culture, DFA or EIA on urethral swabs, and testing of first void
urine. Other options included polymerase chain reaction testing of cervical
specimens in women, first void volume in men, and nucleic acid probes.
Pharmacologic therapy included tetracyclines, erythromycin, azithromycin,
and ofloxacin.
Outcomes
Sensitivity, specificity, test time and costs. Health outcomes for pregnant
women included premature delivery, premature rupture of membranes (PROM),
premature contractions, and pregnancy complications. Outcomes for their
infants included small for gestational age (SGA) infants, perinatal mortality,
pneumonia, conjunctivitis, and total complication rate. Overall costs and
cost-effectiveness were discussed.
Evidence
MEDLINE was searched for 1983 to 1993 using the exploded MeSH heading "Chlamydial
trachomatis" with subheadings "complications", "diagnosis", "drug therapy",
"economics", "epidemiology", "etiology", "history", "microbiology", "mortality",
"prevention and control", "therapy" and "transmission". Study results were
synthesized in table or graphic format only.
Recommendations were graded as:
|
A
|
Good evidence to support the recommendation that the condition
be specifically considered in a PHE. |
|
B
|
Fair evidence to support the recommendation that the condition
be specifically considered in a PHE. |
|
C
|
Poor evidence regarding inclusion or exclusion of the condition
in a PHE, but recommendations may be made on other grounds. |
|
D
|
Fair evidence to support the recommendation that the condition
be specifically excluded from consideration in a PHE. |
|
E
|
Good evidence to support the recommendation that the condition
be specifically excluded from consideration in a PHE. |
Quality of evidence was rated according to 5 levels:
|
I
|
Evidence from at least 1 properly randomized controlled
trial (RCT). |
|
II-1
|
Evidence from well-designed controlled trials without randomization. |
|
II-2
|
Evidence from well-designed cohort or case-control analytic
studies, preferably from more than 1 centre or research group. |
|
II-3
|
Evidence from comparisons between times or places with
or without the intervention. Dramatic results in uncontrolled experiments
could also be included here. |
|
III
|
Opinions of respected authorities, based on clinical experience,
descriptive studies or reports of expert committees. |
Values
The 13-member Task Force of experts in family medicine, geriatric medicine,
pediatrics, psychiatry and epidemiology used an evidence-based method for
evaluating the effectiveness of preventive health care interventions. Recommendations
were not based on cost-effectiveness of options. Patient preferences were
not discussed.
Background papers providing critical appraisal of the evidence and tentative
recommendations prepared by the chapter author were pre-circulated to the
members. Evidence for this topic was presented and deliberated upon in
1- to 2-day meetings from October 1993 to March 1994. Consensus was reached
on final recommendations.
Benefits,
Harms, and Costs
Cervical swab for culture has a sensitivity of 75% to 90% and a specificity
of 100%, but the test is expensive, takes 2 to 3 days and requires specific
technical expertise. Cytologic testing is 95% to 100% sensitive for conjunctivitis,
but has low sensitivity for genital infections. DFA sensitivity and specificity
are 70% to 100% and 85% to 95%, respectively; test time is 15 minutes to
1 hour. EIA takes 3 to 5 hours, has a sensitivity of 37% to 98%, and a
specificity of 85% for cervical infections. Polymerase chain reaction testing
of cervical specimens and first void urine specimens from men is 95% to
100% sensitive and almost 100% specific. Nucleic acid probes are 95% sensitive
and 98% to 100% specific, are available in 2 to 4 hours, but are costly.
3 cohort studies provide evidence of improved pregnancy-related outcomes
with screening and erythromycin therapy. Of 2 smaller studies, one found
no difference in infant complications (pneumonia, conjunctivitis) in treated
and untreated groups, while the other reported that 3/59 (5%) infants of
treated women had complications compared with 5/24 (21%) infants of untreated
women.
No controlled studies have shown that screening of men or non-pregnant
women leads to decreased infection-associated complications.
Economic evaluations support screening under certain conditions. One
decision analysis reported that non-culture or culture tests of asymptomatic
persons could reduce overall costs if disease prevalence was 7% or 14%
respectively. A Canadian study estimated that DFA or EIA screening of women
would be cost effective if the disease prevalence was >6% or 7% respectively.
Mean cost of DFA and EIA was $11. Sensitivity analysis showed that probability
of developing PID and test cost were most important to cost savings. Another
study estimated that DFA testing of pregnant women would be cost effective
if disease prevalence >6% and test cost was <US $6.30.
Recommendations
Recommendation grade [A, B, C, D, E] and level of evidence
[I, II-1, II-2, II-3, III] are indicated after each recommendation. Citations
in support of individual recommendations are identified in the guideline
text.
-
Fair evidence exists to support screening of pregnant women using culture
or polymerase chain reaction for all sites; DFA for genitourinary, conjunctival,
rectal and nasopharyngeal sites; EIAs for genitourinary or conjunctival
specimens; and DNA probes for genitourinary specimens; and treatment with
erythromycin [B, II-2]
-
Fair evidence exists to support screening of persons at high-risk (sexually
active women <25 years, women with new or multiple partners in preceding
year, who use non-barrier contraception or who have cervical friability,
mucopurulent discharge or intermenstrual bleeding) [B,
I, II-2, Modelling].
-
Fair evidence exists to support exclusion of routine screening of the general
population [D, Modelling].
Validation
This report was externally peer-reviewed. The Canadian Expert Interdisciplinary
Advisory Committee on Sexually Transmitted Diseases in Children and Youths
recommended more extensive screening, primarily aimed at diseases other
than chlamydia. The US Centers for Disease Control and Prevention recommend
screening women with mucopurulent cervicitis, sexually active women <20
years, and women who are inconsistent users of barrier contraceptives or
who have new or >1 new partners in past 3 months.
Sponsors
The Canadian Task Force on the Periodic Health Examination
developed this guideline with funding from Health Canada.
Documents
Source
Other
-
Canadian Task Force on the Periodic Health Examination. The periodic health
examination. Can Med Assoc J. 1984;130:1278-85.
Link to Full Text of this
review
Link to Summary Table of Recommendations of this review
Link to Selected References list of this review
Link to 1996 update: Screening for chlamydial
infections
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