Use your browser's BACK button to return to your page of origin.
Impact of switching laboratory tests on reported trends
in Chlamydia trachomatis infections.
American Journal of Epidemiology 2000;151(4):430-435.
Dicker LW, Mosure DJ, Levine WC, Black CM, Berman SM.
Abstract
Improvements in the sensitivity and specificity of laboratory testing methods
for Chlamydia trachomatis infections in recent years have created potential
problems with interpreting data on chlamydia prevalence trends. A switch
to a more sensitive test can result in an increase in chlamydia positivity
even with no increase in the true disease prevalence. To examine the impact
of switching laboratory testing methods on chlamydia positivity trends among
women, the authors analyzed data from chlamydia screening programs in family
planning clinics in two geographic areas of the United States. Data from
7,287 tests performed in Philadelphia, Pennsylvania, indicated a 46% increase
in positivity (from 4.1% to 6.0%) when the clinics switched from a nucleic
acid probe assay to a ligase chain reaction test. Data from 35,306 tests
performed in Oregon and Washington State laboratories showed a 21% increase
in positivity (from 3.3% to 4.0%) when clinics switched from a direct immunofluorescent
antibody testing procedure to an enzyme immunoassay with negative gray zone
confirmation. These increases were within ranges consistent with the variability
of the testing methods and occurred primarily in asymptomatic women and
in women over age 20 years. Any switch in laboratory testing methods must
be considered when interpreting data on chlamydial infection trends.