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C. trachomatis
can be detected in PreservCyt transport medium by the COBAS Amplicor CT/NG
test.
PreservCyt transport medium used for the
ThinPrep test is a suitable medium for detection of Chlamydia trachomatis
by the COBAS Amplicor CT.NG test: results of a preliminary study and
future implications.
Bianchi
A, Moret F, Desrues JM, Champenois T, Dervaux Y, Desvouas O, Oursin
A, Quinzat D, Dachez R, Bathelier C, Ronsin C.
Journal of Clinical Microbiology 2002;40:1740-1754.
Summary:
Question
Can the automated COBAS Amplicor CT/NG test detect C. trachomatis
in cervical specimens collected in PreservCyt transport medium?
Design
This paper describes a prospective study to evaluate the ability of the
automated PCR COBAS Amplicor CT/NG test to detect C. trachomatis in
PreservCyt transport medium used for the ThinPrep Pap test
Participants
Consenting women, aged 15 to 25 years, who presented for Pap screening at
different general practitioners, dermatologists, and family planning
centers in France were studied. One thousand PreservCyt samples were
selected according to the following criteria: 1) they showed normal
cytology, and 2) were from patients who showed no clinical sign of
urogenital infection, including genital or pelvic pain, dysuria, and
urethritis.
Description of Tests and Diagnostic
Standard
PreservCyt (Cytyc Corporation, Boxborough, MA) specimens were first used
to make ThinPrep slides (Cytyc Corporation) for cytological evaluation and
then tested within one week of collection by the COBAS Amplicor CT/NG PCR
assay (Roche Diagnostic Systems, Meylan, France) for the presence of C.
trachomatis. Before testing, 2 ml of sample was centrifuged, the
pellet was suspended in 1 ml of 2-sucrose-phosphate transport medium (2SP,
Roche Diagnostic Systems), and the samples were analyzed according to the
manufacturer's instructions. To confirm positive results, patients whose
PreservCyt samples were positive by Amplicor (absorbance >0.8) were
asked to give a new endocervical swab specimen that was collected and
tested by standard Amplicor CT/NG PCR assay procedures. Positive
PreservCyt specimens were stored at 15 to 20oC for 6 weeks and retested by
the Amplicor assay at 2, 4, and 6 weeks after collection.
Main Outcome Measures
The sensitivity of detection of titered, purified C. trachomatis
elementary bodies in PreservCyt medium compared with that of 2SP transport
medium in a dilution assay, and the results of the Amplicor assay on fresh
and stored PreservCyt specimens were determined.
Main Results
The in vitro sensitivity assay showed that 1 IFU/ml of C.
trachomatis elementary bodies was detected in duplicate from 2SP
medium in 3 of 4 attempts, compared to 1 of 4 attempts when assayed from
PreservCyt medium. Both collection media gave consistently positive
results for duplicate assays performed 4 times on samples seeded with 10
IFU/ml of elementary bodies. C. trachomatis was detected in 22
(2.2%) of the 1000 clinical PreservCyt specimens. All 22 of these samples
were positive on repeat assay of the same PreservCyt sample for up to 6
weeks. No inhibition was observed in any of the samples tested. All 9 of
the 22 positive patients who agreed to be retested with an endocervical
swab placed in 2SP were positive for the Amplicor test.
Authors' Conclusions
PreservCyt transport medium is a suitable
collection medium for routine screening of C. trachomatis
infections with the COBAS Amplicor CT/NG test.
Source of funding: Cytyc France SARL,
and Roche Diagnostics, Meylan, France
For correspondence: Christophe Ronsin,
L. C. L. Service de Biologie Moleculaire, 78 Avenue de Verdun, BP 110,
94208 Ivry sur Seine, France. E-mail address: c.ronsin@lablcl.com.
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