Comparison of first-voided urine specimens with endocervical swab specimens for enzyme-linked immunosorbent assay detection of Chlamydia trachomatis in women
J. A. Kellogg, B. T. Vanderhoff, J. W. Seiple and M. E. Hick
Pathology Department, York Hospital, Pa.
OBJECTIVE: To compare first-voided urine specimens with paired endocervical
swab specimens from women to determine the role of urine in complementing
or replacing swab specimens for the detection of the chlamydial antigen.
DESIGN: For 18 months, both endocervical swab specimens (the criterion
standard) and urine specimens were tested for the chlamydial antigen, using
an enzyme-linked immunosorbent assay (Chlamydiazyme, Abbott Laboratories,
North Chicago, Ill). Positive results were confirmed using a blocking
reagent (Abbott Laboratories) and/or a direct fluorescent antibody test
(Micro-Trak, Syva, Palo Alto, Calif). A low level of chlamydial antigen
(below the enzyme-linked immunosorbent assay threshold recommended by the
manufacturer) was also looked for and, when found, was confirmed by the
direct fluorescent antibody test. SETTING: Prenatal and family practice
clinics in a 500-bed community hospital. PATIENTS: Specimens were collected
from 489 random asymptomatic or symptomatic women. MAIN OUTCOME MEASURE:
The detection of the chlamydial antigen from endocervical swab specimens
was compared with the detection from first-voided urine specimens. RESULTS:
Acceptable swab and urine specimens were obtained from 300 (61.3%) of the
patients. The antigen of Chlamydia trachomatis was confirmed in 20 (6.7%)
of the 300 women. Of the infected patients, the antigen was detected in
both swab and urine specimens for nine patients (45%), only in the swab
specimens for eight (40%), and only in the urine specimens for three (15%).
Testing urine in addition to endocervical swab specimens allowed for the
detection of 18% more chlamydial infections, whereas confirming the
presence of the antigen below the enzyme-linked immunosorbent assay cutoff
resulted in the detection of 54% more infections. CONCLUSIONS: Collecting
multiple specimens and testing for low levels of chlamydial antigen may
significantly improve the detection of chlamydial infections in women.
First-voided urine may be an appropriate complementary specimen to
endocervical swab specimens, but urine by itself does not allow for the
adequate detection of the chlamydial antigen in women.
