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Evaluation of syphilis reactor grids: optimizing impact
Joshua K Schaffzin1, Emilia H Koumans, Richard H Kahn
1Division of STD Prevention, National Center for HIV, STD, and TB Protection, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA.
Background:
A syphilis reactor grid (SRG) is an administrative tool based on the sex, age, and serologic titer of persons with reactive serologic tests for syphilis (reactors) that is used by Sexually Transmitted Disease program staff to prioritize follow-up investigations of persons who may have syphilis. The National Plan to Eliminate Syphilis from the United States recommends that state and local health departments regularly evaluate the effectiveness of their SRGs. However, there are limited methods for SRG evaluation that are feasible for sexually transmitted disease programs.
Goal:
To evaluate the sensitivity and predictive value of five currently used SRGs.
Study Design:
Comparative evaluation of five SRGs in four different populations.
Results:
The percentage of true syphilis cases not assigned to an investigation by an SRG (missed cases) was dependent on syphilis prevalence among reactors and on the SRG. The percentage of reactors assigned to an investigation by an SRG that were not true cases was primarily dependent on syphilis prevalence among reactors, not SRG design. Cases missed by SRGs were predominantly men aged 30 to 50 years and women aged 20 to 40 years who had low or intermediate serologic titers.
Conclusion:
Monitoring the prevalence of syphilis among reactors is critical because in areas with high prevalence, most SRGs miss a substantial number of cases, and in areas with low prevalence, some SRGs can reduce unnecessary investigations.