Correlation Between Repeat Chlamydia Testing and Chlamydia Positivity Rates at Family Planning Clinics

Background:
Following prior declines, chlamydia positivity rates have plateaued or increased in recent years in many regions of the United States. While such trends may reflect increasing chlamydia prevalence, increases in reported positivity rates may also reflect increased testing of individuals at high risk of chlamydia.

Objective:
This study was designed to test whether increased testing of women who previously tested positive for chlamydia is correlated with an increase in chlamydia positivity.

Method:
Chlamydia positivity monitoring data, collected through the National Infertility Prevention Project (IPP), were analyzed for 187 family planning clinics in Pennsylvania, Virginia, and West Virginia. Correlation analysis was performed to determine whether changes in chlamydia positivity between 2000 and 2005 correlated with the percentage of repeat testing. Repeat tests were defined as those administered between 30 and 365 days of a positive chlamydia test in the previous calendar year.

Result:
Between 2000 and 2005, overall chlamydia positivity rate in females tested at the selected clinics rose from 4.14% to 5.78%. The change in chlamydia positivity at individual clinics ranged from –4.35% to +10.12%. The percentage of total tests that followed a positive chlamydia test in the prior calendar year rose slightly, from 0.56% to 0.64%; at individual clinics, the change in the percentage of repeat testing ranged from
–2.19% to +2.54%. Positivity of repeat tests was higher than overall positivity. (12.92% vs. 4.14% and 13.55% vs. 5.78% in 2000 and 2005, respectively). The change in the percentage of repeat tests at each clinic was significantly correlated (p=0.01) with the change in chlamydia positivity at that clinic.

Conclusion:
Repeat testing was found to correlate significantly with chlamydia positivity trends in female family planning clients.

Implications:
When trends in chlamydia positivity are evaluated for program planning, the effect of repeat testing on positivity should be considered.