Incorrect STD tests show need for
patients' sex histories
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By Helen Altonn
haltonn@starbulletin.com
False-positive gonorrhea tests for five Honolulu women in an eight-month
period underscore the importance of doctors getting sexual history for
patients, says Dr. Alan Katz, University of Hawaii epidemiology professor
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Sensitivity of only 61.9%--75.3% !!!!!!!!!!!
C. trachomatis Tests for Screening Women and Men
Sensitivity
Reviews of screening tests for C. trachomatis conclude that sensitivities
of commercial NAATs exceed those of non-NAATs (14--23). A substantial
proportion of the published evaluations of NAATs cited in these reviews
have relied on discrepant analysis. However, certain studies permit the
calculation and comparison of NAAT and non-NAAT sensitivities by using
culture as an independent reference standard. A five-center study
reported
sensitivities of NAATs for endocervical specimens that exceeded the
sensitivity of a nonamplified nucleic acid hybridization test by 19.7%
(95% confidence interval [CI] = 12.9%--26.6%) for LCR and 12.4% ( 95% CI =
2.1%--22.7%) for PCR (78). The sensitivities of LCR and PCR were slightly
lower when performed on urine specimens than on endocervical specimens
(83.4% versus 91.4% and 79.5% versus 84.0% , respectively).
The sensitivity of the nonamplified hybridization test (71.6%) was similar
to that reported in an earlier study (75.3%) that compared the
hybridization test, three EIAs, and a DFA performed on endocervical swab
specimens by using culture as the reference standard (79). Sensitivities
of the tests evaluated in that study were 61.9%--75.3%.
Culture, a NAAT (LCR), and the nonamplified hybridization test have also
been compared by using an independent reference standard (78). For this
evaluation, the reference standard was a positive PCR performed on an
endocervical or urine specimen. For endocervical swab specimens, the
sensitivity of LCR (85.5%) exceeded that of culture (74.7%) by 10.8% and
that of the hybridization test (61.9%) by 23.6%. For the urine specimen,
the sensitivity of LCR was 80.8%.
A limited number of studies have used an independent reference standard to
compare the sensitivities of tests for detection of C. trachomatis
infection in asymptomatic men. One five-center study compared LCR and PCR
performed on urine from asymptomatic males by using culture of
intraurethral swab specimens as the independent reference standard (80).
The sensitivities of LCR (84.4%) and PCR (85.4%) were similar.