Structural Intervention to Reduce Chlamydia Screening Among Females Aged Over 25 in San Francisco

Background: Chlamydia screening is recommended for females 25 years of age and younger, given this population is at the highest risk of infection.  Screening of older women is often cost-inefficient.  In San Francisco, a significant amount of resources have been devoted to screening females aged over 25 for chlamydia.

Objectives: To evaluate a structural intervention aimed at reducing chlamydia screening among females aged over 25 at sites in the San Francisco STD Screening Program.

Methods: Screening Program sites submit specimens with laboratory requisition forms listing the valid categories for diagnostic or screening as outlined in the San Francisco Screening Guidelines.  Beginning on January 1, 2009, any specimen submitted to the laboratory without a reason for testing listed on the requisition form is not tested.  We compared testing volume and positivity from eight Screening Program sites during the first half of 2008 and the first half of 2009.

Results: During the first half of 2008, 837 chlamydia tests were run on females over 25 years of age, identifying 21 new infections (2.5% positivity).  During the first half of 2009, 655 chlamydia tests were run on females over 25 years of age, identifying 22 infections (3.4% positivity).  Compared to the first half of 2008, in the first half of 2009, the number of chlamydia tests submitted to the public health laboratory in females aged over 25 declined 22% while declining 11% in females 25 and younger. One additional chlamydia infection was identified in the older population in 2009 compared to 2008.

Conclusions: Following the implementation of a structural intervention unnecessary chlamydia testing among older females was reduced by 22% without impacting case finding.

Implications for Programs, Policy, and/or Research: Structural interventions to reduce chlamydia overscreening can be successfully implemented.