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Two amplification
assays performed better than a non-amplification assay for the
detection of C. trachomatis.
Comparative evaluation
of BDProbeTec ET, LCx, and PACE 2 assays for the detection of Chlamydia
trachomatis in urogenital samples.
Pollara C, Terlenghi L, De Francesco MA,
Gargiulo F, Perandin F, Manca N.
European
Journal of Clinical Microbiology & Infectious Diseases
2003;22:512-14.
Summary:
Question
How well do two commercial nucleic acid amplification assays (ligase chain
reaction and strand displacement amplification) compare to a probe
hybridization assay for the detection of C. trachomatis in
specimens collected from men and women?
Design
Two commercial nucleic acid amplification assays were compared to a
non-amplification assay for the detection of C. trachomatis in
endocervical and urethral specimens that were collected from women and
men, respectively, who were at low risk of chlamydial infection.
Participants
The study population included 239 women and 61 men, aged 18 to 50 years
(mean age = 24 years), treated at a hospital in Brescia, Italy.
Thirty-seven women and 13 men had probable infertility, were asymptomatic,
and had not received antimicrobial treatment in the previous month. Two
hundred two women were seen for routine gynecologic or pregnancy
examinations, and 48 men were seen for a variety of symptoms.
Description of Tests and Diagnostic
Standard
Three endocervical swabs from each woman and three urethral swabs from
each man were collected, transported, and stored according to the
manufacturers' directions for the assay being performed. The first swab
was used for a Gram stain and then for the BDProbeTec ET strand
displacement amplification assay (BDPT, Becton Dickinson, USA), the second
swab was used for the PACE 2 probe hybridization assay (Gen-Probe, USA),
and the third swab was used for the LCx ligase chain reaction assay
(Abbott Laboratories, USA), according to the manufacturers' directions. A
subset of 37 women and 13 men provided urine samples for analysis by the
two nucleic acid amplification assays. Specimen adequacy was evaluated by
examining the Gram stained slides for epithelial cells. Swabs and urine
specimens were considered positive for C. trachomatis if both
nucleic acid amplification assays were positive.
Main Outcome Measures
The sensitivity, specificity, positive predictive value (PPV), and
negative predictive value (NPV) of each of the three methods for the
detection of C. trachomatis in endocervical, urethral, and urine
specimens were determined.
Main Results
C. trachomatis was detected in 7 (2.3%) of 300 endocervical and
urethral specimens and in 1 of 50 urine specimens. The two nucleic acid
amplification methods were 100% sensitive and specific for C.
trachomatis detection in all specimens. The PACE 2 assay detected C.
trachomatis in 2 of 2 and in 2 of 5 positive urethral and endocervical
specimens, respectively. The 3 specimens found positive by LCx and BDPT
and negative by PACE 2 were confirmed positive by a second ligase chain
reaction assay that used primers for the C. trachomatis major outer
membrane protein.
Authors' Conclusions
The two nucleic acid amplification assays
were more sensitive than the non-amplification assay for the detection of C.
trachomatis among women with a low prevalence of infection.
Source of funding: None given
For correspondence: C. Pollara,
Institute of Microbiology and Virology, Spedali Civili Hospital, Piazza
Spedali Civili 1, 25123 Brescia, Italy. E-mail address: pollara@bshosp.osp.unibs.it.
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