PARTNER SERVICES PROGRAMS FOR CHLAMYDIAL INFECTION: A COMPARISON BETWEEN PARTNER NOTIFICATION AND EXPEDITED PARTNER THERAPY

Purpose:

   Partner services are important to test and treat individuals at high risk of chlamydial infection and to prevent onward transmission and/or re-infection. Partner notification (PN), the most common partner strategy, relies on the index patient or provider notifying sexual partners and providing referral information. However, the rate of partner follow-up under PN can be low. Expedited partner therapy (EPT) allows the index patient to deliver antibiotic regimens to sexual partners, eliminating the need to seek care but increasing the likelihood of over-treatment. We identify strategy-based differences varying with the level of external exposure to risk in chlamydia incidence, pelvic inflammatory disease (PID) incidence, and average duration of infection. Additionally, we quantify EPT over-treatment.

Methods:

   We developed a Markov model to simulate 10,000 chlamydia infected heterosexual couples aged 15-24 for 3 years with a cycle length of one month under two strategies: PN and EPT, modeled separately with imperfect compliance. The probability of infection combines the transmission from intra- and extra-relational contacts to capture the internal and external exposure to the risk. We assumed that the average intra-relational contacts were 8 times per month based on the literature and varied the extra-relational sex acts per month from 0 to 20. The internal probability of infection is 0.464 and the external probability ranges from 0 to 0.1. We assumed that over-treatment only happens with EPT.

Results:

   The Figure shows the relative effects of EPT to PN for chlamydia and PID incidence as the number of extra-relational sex acts increases. Compared to PN, EPT averts from 2,064 (11.4%) chlamydial infections to 84 (0.1%) as the number of extra-relational sex acts increases. Regarding PID infections, EPT reduces the infections from 198 (8.9%) cases to 111 (2.4%) cases with increasing number of extra-relational sex acts. Although EPT has shorter durations than PN, the differences in days are small (less than 3 days) between them. The number of over-treated partners for EPT varies from 291 to 684.

Conclusions:

   Although EPT prevents more chlamydial and PID infections than PN, as the number of extra-relational sex acts increases, the superiority of EPT diminishes. Additionally, with a time horizon of 3 years, EPT only reduces the durations less than 3 days for both infections and over-treats partners with increasing external risk.