Background CDC recommends sexually active females aged <26 be screened annually for Chlamydia trachomatis (Ct). Only Ct cases are reported to local health departments. Screening coverage estimates, defined as the proportion of the sexually active population tested for Ct, are not routinely available. Without such measures it is difficult to interpret increases in Ct case reports.

Methods We compared 2 approaches to estimating screening coverage in the New York City neighbourhood of Central Brooklyn (CB) in 2009: The “indirect method” used public health surveillance data, and “back calculated” to get the number of sexually active females that must have been screened to yield the number of reported Ct cases in CB females aged 15–19 and 20–25 years. Data inputs included: reported number of females with ≥1 Ct case in 2009 (730 cases aged 15–19, 619 cases aged 20–25) population estimates (12 772 aged 15–19, 14 024 aged 20–25), proportion ever had sex (35% aged 15–19), proportion sexually active in last 12 months (76% aged 20–25), and Ct positivity (20% aged 15–19, 8% aged 20–25). The “direct method” used electronic health record (EHR) data from 8 primary care provider practices in CB and adjoining zip codes using a common EHR for >1 year. EHR data were analysed to determine: numbers of unduplicated female clients aged 15–19 and 20–25, proportion sexually active, and number of sexually active females screened for Ct. The sexually active population was measured in 2 ways; group 1 was defined as females that reported ever having sex (18% (246/1340) aged 15–19 and 12% (302/2419) aged 20–25). Group 2 was defined as females meeting >1 of: reported ever having sex; ever prescribed an oral contraceptive by the practice; ever had an STD; ever diagnosed with STD by the practice; ever pap ordered by the practice (38% (514/1340) aged 15–19 and 38% (910/2419) aged 20–25).

Results See Abstract P1-S6.19 table 1.

Conclusion The indirect approach yielded a higher Ct screening coverage estimate than the direct approach. By both methods, screening coverage was higher in the 15–19 age group than the 20–25 age group. For the direct approach, definitions of sexually active women affected measures of screening coverage, particularly for 15–19 year olds. The indirect method can be easily replicated, with limited resources. The direct method requires more resources and is contingent on consistent and accurate provider documentation of sexual activity.