Trends in Demographic Characteristics and Risk Factors among Individuals with Syphilis in Colorado from 2011-2020.

Background: Identify opportunities to improve syphilis screening by describing changes in patient characteristics and risk factors among individuals with syphilis and by comparing cases with and without an indication for syphilis screening.

Methods: This retrospective cohort study used Colorado public health surveillance data to identify 8,326 syphilis diagnoses from 2011-2020. Demographics, clinical characteristics, and risk factors were compared across 2-year groups and between individuals with and without an indication for screening. Indications for screening were based on national guidelines and included men who have sex with men, persons living with HIV, pregnant individuals, those who test positive for chlamydia, gonorrhea, or HIV, and partners of those who test positive for syphilis.

Results: Across study years, there was a 234% increase in the proportion of syphilis cases that were females (5.3% to 17.7%; p < .01), a 78% increase in the proportion of cases living in rural areas (3.6% to 6.4%; p < .01), and a 15% increase in the proportion of cases among non-White individuals (47.9% to 54.9%; p < .01). The proportion of patients that had a guideline-recommended indication for screening decreased from 88% in 2011-2012 to 59% in 2019-2020 (p < .01). Females represented 5.5% of cases with an indication for screening and 29.8% of cases without an indication for screening (p < .01).

Conclusions: Syphilis cases increased annually from 2011-2020 yet the proportion of cases detected under current screening recommendations decreased. These findings reveal opportunities to expand syphilis screening.