Background:
Annual Chlamydia (CT) screening of sexually-active women age <25 is recommended. Targeted screening is recommended for women >25, but it is unclear who specifically should be targeted. More explicit CT screening criteria, sensitive for identifying infection and specific for reducing screening in uninfected patients, are needed for women >25, and could be valuable for some low-risk populations of women age 21-25.

Objective:
To identify CT-associated risk factors and to assess the predictive value of various screening algorithms among non-pregnant, female patients over age 20.

Method:
Between 2003-2005, patient data were collected via self-administered risk factor questionnaires, clinical evaluations, and laboratory databases for over 4,300 sexually-active, non-pregnant, female family-planning patients age 21-30, who were tested for CT at 9 California clinics. Data collected included demographics; symptoms; clinical signs and diagnoses; STD history and exposure; relationship status; sexual-behavior risk factors; and chlamydia and gonorrhea test results. Analyses stratified patients by age groups 21-25 and 26-30.

Result:
Patients with STD exposure, CT-associated clinical syndromes (cervicitis, PID), or another STD, comprised 25% of CT cases. Of the remaining patients without clear diagnostic reasons for testing, those reporting multiple partners or partners with possible concurrent partners during the past year were more likely to be infected in both age groups. Current BV was also a predictor of infection for both groups, as was African-American race and CT history in the past year for the younger women. Screening algorithms using combinations of these factors captured between 80-90% of CT cases and reduced overall screening by 40-50%, and were especially predictive for women age >25.

Conclusion:
An efficient strategy for CT case-finding includes: diagnostic testing; secondary screening for patients with current STDs, including BV; and routine screening targeting primarily those patients reporting multiple partners or possible non-monogamous partners.

Implications:
Targeted screening strategies can be developed to optimize case-finding and reduce unnecessary screening.