|
The first 20 to 30
ml of urine is the optimal collection for detection of C.
trachomatis by four nonculture assays performed on urine samples
from men.
Impact of urine
collection order on the ability of assays to identify Chlamydia
trachomatis infections in men.
Chernesky M, Jang D, Chong S, Sellors J,
Mahony J.
Sexually
Transmitted Diseases 2003;30:345-347
Summary:
Question
What is the ability of four different nonculture assays to detect C.
trachomatis infection in men by analyzing urine samples collected
sequentially as first, second, and third void specimens?
Design
This study describes a comparison of the results of four nonculture assays
performed on three sequential volumes of urine collected in separate
containers from men also undergoing urethral swabbing and culture for the
detection of C. trachomatis infection.
Participants
Two hundred thirty-seven men attending an STD clinic were tested.
Description of Tests and Diagnostic
Standard
Each patient collected three containers of urine, each containing 20 to 30
ml, representing the first-void, second-void, and third-void urine
samples. All specimens were held at 4oC and shipped to the
testing laboratory within 24 h. Each urine sample was tested for C.
trachomatis infection using 4 methods. 1) For the ligase chain
reaction (LCR) (LCx, Abbott), 1 ml of urine was centrifuged, the pellet
was suspended in 1 ml of kit resuspension buffer, and the assay was
performed as previously described. All positive samples were confirmed
positive with an in-house PCR. 2) For the nucleic acid hybridization assay
(NAH), 3 ml of urine were centrifuged, the pellet suspended in 200 μl
PACE 2 swab transport buffer, incubated for 15 to 30 min at room
temperature, and a 100 μl sample was tested by PACE 2 (GenProbe)
according to the kit package insert. 3) For the enzyme immunoassay (EIA),
10 ml of urine were centrifuged, the pellet was suspended in 1 ml of
buffer, and tested according to the Chlamydiazyme kit (Abbott) package
insert for swab specimens. All positive samples were confirmed positive
using the blocking confirmation reagent (Abbott). 4) A leukocyte esterase
(LE) test (Chemstrip 2LN, Boehringer Mannheim) was performed on each urine
sample and scored as positive if the reading was >1+ after 2 minutes.
Following urination, a urethral swab was collected, placed into a tube of
culture transport medium, and inoculated onto McCoy cell monolayers.
Main Outcome Measures
The prevalence of C. trachomatis infection in each of the 3 voids
of urine obtained by each of 4 assays were compared with the C.
trachomatis culture results of the urethral swabs.
Main Results
Culture of the urethral swab detected C. trachomatis in 6 (2.5%) of
237 samples. The results of the 4 nonculture assays performed on 3 voids
of urine from each of 237 men are shown in the table. The highest
prevalence was detected with LCR. EIA, NAH, and LE did not detect any
extra positives not detected by LCR for any of the voids.
Authors' Conclusions
All of the assays showed a sharp decrease in
the number of positive samples detected in the second and third urine
voids compared to the first. Nucleic acid amplification testing of first
void urine was the most effective method for diagnosing C. trachomatis
infection in these men.
Source of funding: None given.
For correspondence: Max A. Chernesky,
Medical Microbiology Services, McMaster University Regional Virology and
Chlamydiology Laboratory, St. Joseph's Healthcare, 50 Charlton Avenue
East, Hamilton, ON L8N 4A6, Canada. E-mail address: chernesk@mcmaster.ca.
|
.gif){kind=small}