Reactor Grids for Prioritizing Syphilis Investigations: Are Primary Syphilis Cases Being Missed?

Evaluation of Automated Processing of Electronically Reported Serological Tests for Syphilis Using Current and Historical Syphilis Results Compared With Traditional Reactor Grid Processing in Florida

BACKGROUND

Syphilis in Florida increased 49% from 2016 to 2020. Moreover, many serological tests for syphilis (STS) do not indicate current infection. Traditionally, syphilis surveillance systems used reactor grids, a method for prioritizing STS for investigation based on age, nontreponemal titer, and/or sex. In 2022, Florida's sexually transmitted disease surveillance system implemented an automated method for processing electronically reported STS (eSTS), expanding upon the reactor grid, using an individual's current STS (treponemal and nontreponemal), treatment history, and historical STS results aiming for more efficiently processing eSTS. We compared the new method of processing eSTS results against the reactor grid and determined potential value in time/cost savings of this change.

METHODS

All eSTSs (n = 4144) from January 2, 2023 to January 8, 2023, were compared by how the logic-based method processed test results versus how the reactor grid processed test results. Each method was compared using measurements of accuracy (e.g., sensitivity/specificity). Time and cost savings in eSTS processing were estimated.

RESULTS

Using the surveillance case definition as reference, the accuracy of the logic-based method for processing eSTS was nearly double (82.3% vs. 43.6%), had greater specificity (79.0% vs. 33.0%), and increased positive predictive value (47.5% vs. 22.0%) when compared with the reactor grid method. Sensitivity (99.5% vs. 98.6%) and negative predictive value (99.9% vs. 99.2%) remained similar. The logic-based method is estimated to save 7783 hours annually (~$185,000).

CONCLUSIONS

Processing eSTS based on current and historical STS results is significantly more accurate than using a reactor grid. Moreover, these improvements save time and resources that can be better allocated to other program prevention activities.

Access to Benzathine Penicillin G Treatment for Persons With Syphilis, Maricopa County, Arizona, 2021

BACKGROUND

As the incidence of syphilis continues to increase, examining benzathine penicillin G (BPG) treatment data provides valuable insight for public health strategies. This study analyzed the trends of where BPG is administered relative to the initial clinical site of syphilis diagnosis. Our findings are timely in the context of recent national BPG shortages.

METHODS

The analysis included persons diagnosed with any syphilis stage in Maricopa County, Arizona, from January 1, 2021, to December 31, 2021. The Arizona surveillance database (PRISM) was the source of demographic, testing, and treatment data.

RESULTS

Of a total of 4028 persons with syphilis, 3038 (75.4%) received at least 1 injection of BPG. Among persons who received an initial BPG injection, only 1719 (56.6%) were diagnosed and treated at the same clinical site type. The Maricopa County Sexually Transmitted Disease Clinic administered BPG to 48.8% (n = 1483) of persons with syphilis who received an initial injection.

CONCLUSIONS

Our findings analyze trends in BPG administration that are likely due to treatment referral practices and medication cost. Administration of BPG is not guaranteed at the clinical site of diagnosis, highlighting concerns regarding access to BPG. A burden is placed on patients who are required to leave their diagnosing provider to seek syphilis treatment at other health facilities that administer BPG.

An Automated Syphilis Serology Record Search and Review Algorithm to Prioritize Investigations by Health Departments

BACKGROUND

Reactive syphilis serologies are investigated by health departments to determine if they represent new infection, reinfection, or treatment failure. Serologies prioritized for investigation based on nontreponemal test titer and age (using a "reactor grid") undergo manual record search and review. We developed a computerized algorithm that automates the record search and review.

METHODS

We developed and tested the algorithm using a Florida Department of Health data set containing serologies reported January 2016 to December 2018 and previous records linked to each individual. The algorithm was based on the syphilis case definition, which requires (except primary cases with signs and symptoms) (1) a positive treponemal test result and a newly positive nontreponemal test result or (2) a 4-fold increase in nontreponemal test titer. Two additional steps were added to avoid missing cases. New York City Department of Health and Mental Hygiene validated this algorithm.

RESULTS

The algorithm closed more investigations (49.9%) than the reactor grid (27.0%). The algorithm opened 99.4% of the individuals investigated and labeled as cases by the health department; it missed 75 cases. Many investigations opened by the algorithm were closed by the reactor grid; we could not assess how many would have been cases. In New York City, the algorithm closed 70.9% of investigations, likely because more individuals had previous test in the database (88.2%) compared with Florida (56.5%).

CONCLUSIONS

The automated algorithm successfully searched and reviewed records to help identify cases of syphilis. We estimate the algorithm would have saved Florida 590 workdays for 3 years.

Enhancing the Control of Syphilis Among Men Who Have Sex With Men by Focusing on Acute Infectious Primary Syphilis and Core Transmission Groups

The syphilis epidemic among men who have sex with men (MSM) has been increasing steadily. Many syphilis control programs focus on assuring treatment of all persons diagnosed with early syphilis without prioritizing acute primary syphilis or specific subgroups. Acute primary syphilis is highly infectious and contributes to a high proportion of new cases. Surveillance data show that among MSM with incident syphilis (primary or secondary) only about 35% are identified in the primary stage, indicating that most primary cases are missed and untreated. Patients with primary syphilis and large numbers of sex partners may play a major role in maintaining syphilis transmission. Considering those issues, sexually transmitted disease (STD) programs should consider increasing their focus on primary syphilis by assigning primary cases the highest priority, expanding client and clinician health education, and increasing the detection of primary syphilis through increased serologic screening frequency among high-risk MSM. Furthermore, syphilis control programs should implement steps to identify asymptomatic high-probable occult primary cases based on low titer (≤1:8) and recent seroconversion. Finally, to address core transmission groups, programs should implement periodic risk assessment to identify persons with a high number of sex partners and offer these individuals risk-reduction counseling, case management, and selective syphilis preexposure or postexposure doxycycline chemoprophylaxis. Although reprioritizing prevention efforts might be challenging, the Centers for Disease Control and Prevention, community advocacy groups, university STD research centers, and national STD prevention training centers can assist by providing support for consensus discussions and direction in developing operational guidance, some of which may be best delivered through STD and human immunodeficiency virus program partnerships.

Frequency and Characteristics of Biological False-Positive Test Results for Syphilis Reported in Florida and New York City, USA, 2013 to 2017

Discordant syphilis test results, with a reactive nontreponemal test and nonreactive treponemal test are usually considered biological false-positive test results (BFPs), which can be attributed to other conditions. Syphilis surveillance laws mandate laboratory reporting of reactive syphilis tests, which include many BFPs. We describe the frequency of BFPs, titer distributions, and titer increases from reported test results in Florida and New York City (NYC). Reactive nontreponemal tests for individuals with at least one nonreactive treponemal test and no reactive treponemal test were extracted from sexually transmitted disease (STD) surveillance systems in Florida and NYC from 2013 to 2017. Characteristics of individuals with BFPs were analyzed after selecting the observation with the highest titer from each individual. We next considered all results from individuals to characterize persons who had a 4-fold titer increase between successive nontreponemal tests. Among 526,540 reactive nontreponemal tests, there were 57,580 BFPs (11%) from 39,920 individuals. Over 90% (n = 52,330) of BFPs were low titer (≤1:4), but 654 (1%) were high-titer BFPs (≥1:32). Very high-titer (≥1:128) BFPs were more common among individuals over 60 years of age (odds ratio [OR], 2.68; 95% confidence interval [CI], 1.22 to 5.91). A 4-fold increase in titer was observed among 1,863 (14%) individuals with more than one reported BFP. Most BFPs detected by surveillance were low titer, but some were high titer and some had a 4-fold increase in titer. Review of patient histories might identify underlying conditions contributing to these high and rising titers.