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Reactor Grids for Prioritizing Syphilis Investigations

Are Primary Syphilis Cases Being Missed?

Cha, Susan, PhD, MPH*†; Matthias, James M., MPH*‡; Rahman, Mohammad, PhD, MBBS, MPH; Schillinger, Julia A., MD, MSc; Furness, Bruce W., MD, MPH*∥; Pugsley, River A., PhD, MPH***; Kidd, Sarah, MD, MPH*; Bernstein, Kyle T., PhD, SCM*; Peterman, Thomas A., MD, MSc*

doi: 10.1097/OLQ.0000000000000833
Original Studies

Background Health departments prioritize investigations of reported reactive serologic tests based on age, gender, and titer using reactor grids. We wondered how reactor grids are used in different programs, and if administratively closing investigations of low-titer tests could lead to missed primary syphilis cases.

Methods We obtained a convenience sample of reactor grids from 13 health departments. Interviews with staff from several jurisdictions described the role of grids in surveillance and intervention. From 5 jurisdictions, trends in reactive nontreponemal tests and syphilis cases over time (2006–2015) were assessed by gender, age, and titer. In addition, nationally-reported primary syphilis cases (2013–2015) were analyzed to determine what proportion had low titers (≤1:4) that might be administratively closed by grids without further investigation.

Results Grids and follow-up approaches varied widely. Health departments in the study received a total of 48,573 to 496,503 reactive serologies over a 10-year period (3044–57,242 per year). In 2006 to 2015, the number of reactive serologies increased 37% to 169%. Increases were largely driven by tests for men although the ratios of tests per reported case remained stable over time. Almost one quarter of reported primary syphilis had low titers that would be excluded by most grids. The number of potentially missed primary syphilis cases varied by gender and age with 41- to 54-year-old men accounting for most.

Conclusions Reactor grids that close tests with low titers or from older individuals may miss some primary syphilis cases. Automatic, computerized record searches of all reactive serologic tests could help improve prioritization.

Reactor grids may miss low-titer primary syphilis cases.

From the *Division of Sexually Transmitted Diseases Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention,

Division of Scientific Education and Professional Development, Center for Surveillance, Epidemiology, and Laboratory Services, Centers for Disease Control and Prevention, Atlanta, GA;

Florida Department of Health, Tallahassee, FL;

§Louisiana Department of Health-Office of Public Health-STD/HIV Program, Baton Rouge, LA;

New York City Department of Health and Mental Hygiene, Long Island, NY;

Washington DC Health Department, Washington, DC; and

**Virginia Department of Health, Richmond, VA

Acknowledgements: Dayne Collins (Division of STD Prevention, CDC), Anna B. Cope (Division of STD Prevention, CDC), Felicia M.T. Lewis (Division of STD Prevention, CDC), Ryan Kreisberg (Arizona Department of Health Services), The California Department of Public Health, Stephanie Green (Kansas Department of Health and Environment), Robin R. Hennessy (Division of STD Prevention, CDC, New York City Department of Health and Mental Hygiene), Kristen Eberly (Oklahoma State Department of Health), Lyn Trotter (Pennsylvania Department of Health), and Sydney Minnerly (Texas Department of State Health Services).

Conflict of Interest and Sources of Funding: None declared.

The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention.

Correspondence: Susan Cha, PhD, MPH, Centers for Disease Control and Prevention, 1600 Clifton Rd, Atlanta, GA 30329. E-mail:

Received for publication October 24, 2017, and accepted March 5, 2018.

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© Copyright 2018 American Sexually Transmitted Diseases Association