Limited Utility of Reverse Algorithm Syphilis Testing in HIV Clinic Among Men Who Have Sex With Men

Area of Science:

• Infectious Diseases
• Clinical Diagnostics
• Public Health

Background:

• The reverse algorithm for syphilis diagnosis involves treponemal antibody screening followed by nontreponemal antibody testing.
• Its use is increasing in the US, but cost-effectiveness in high-prevalence populations is debated.

Purpose of the Study:

• To evaluate the efficiency of the syphilis reverse algorithm in a high-prevalence population.
• To assess the performance of the reverse algorithm in men who have sex with men (MSM) attending an HIV clinic.

Main Methods:

• Retrospective cross-sectional study of 1693 MSM tested between March 2015 and February 2017 in an Alabama HIV clinic.
• Used Trep-Sure enzyme immunoassay (EIA) for screening, followed by rapid plasma reagin (RPR) testing for reactive screens.
• Analyzed sociodemographic, clinical data, and quantitative EIA index values.

Main Results:

• 48% of MSM had a positive initial EIA screen.
• 53% of those with positive EIA screens had nonreactive RPR results (EIA+/RPR-).
• A modified EIA index threshold (>8) showed improved test performance compared to the current threshold (1.2).

Conclusions:

• The syphilis reverse algorithm was inefficient in this MSM cohort due to high rates of prior syphilis and false-positive EIA screens.
• Frequent syphilis screening is crucial for epidemic response in high-prevalence populations.
• The traditional syphilis testing algorithm is recommended for these groups.