BACKGROUND: As the number of sexually transmitted diseases (STD) cases continues to increase in Washington State (WA), it is important to identify high-risk groups within a population to help state and local health departments refine testing guidelines for chlamydia and gonorrhea. The purpose of this analysis was to determine differences in positivity rates among sub-populations and whether WA Department of Health (DOH) is targeting the appropriate populations for testing (Safety Net).
METHODS: January – June 2015 STD testing data from three different data sources were used to compare positivity rates for chlamydia and gonorrhea. Facility visit data from STD Surveillance Network (SSuN) included: 1) All patients from an urban STD clinic (STD clinic); and, 2) Female patients aged 15-44 from 21 family planning clinics in Western Washington (FP clinics). The third data source was laboratory results of chlamydia and gonorrhea tests of un- and under insured patients from clinics that WA funds (Safety Net). We calculated differences in positivity rates per 100 by total population, gender, age (15 - 24 vs 25 - 44), and insurance status. Since the FP Clinic data included only female patients, subset data from the STD clinic and Safety Net included only females when comparing across all three data sources.
RESULTS: For chlamydia, the STD clinic’s overall positivity rate was significantly higher than Safety Net’s positivity rate (12.1 vs 6.7, p<0.001) as well as in age groups 15-24 (12.0 vs 8.1, p=0.02) and 25-44 (12.2 vs 4.7, p<0.001) and males (13.6 vs 7.7, p<0.001). Similarly for gonorrhea, the STD clinic’s overall positivity rate was significantly higher than Safety Net’s positivity rate (11.7 vs 1.8, p<0.001) as well as in 25-44 year olds (12.3 vs 2.1, p<0.001) and females (13.4 vs 1.4, p<0.001). For gonorrhea, FP Clinic positivity rate was significantly lower than Safety Net’s positivity rates. Safety Net had a higher positivity rates among females aged 15-24 (1.8 vs 0.9, p=0.02) and those underinsured (3.0 vs 0.1, p=0.01). For chlamydia, there were no significant differences identified between the FP Clinics and Safety Net.
CONCLUSIONS: The results determined there are specific sub-populations (those ages 15 – 24, females, and those under-insured) that should be recommended for screening. Healthcare professionals may need to be more aware of sub-populations that have higher positivity rates than others. Results need to be discussed within WA DOH in order to target populations at a higher risk for STD.