School of Public Health

Fighting America’s syphilis outbreak with an app

UW Epi News
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Monday, November 13, 2017

Syphilis, once an all but eradicated disease in the United States, appears to be making a worrisome comeback. Cases of the sexually transmitted infection (STI) have increased 17.6% from 2015 to 2016, according to the Centers for Disease Control and Prevention.

Unlike most bacteria, T. pallidum - the bacteria responsible for syphilis - cannot be cultured in a laboratory, making it more difficult to diagnose and treat.

Diagnosis for syphilis depends on a number of things, including a person’s previous lab reports, physical symptoms, and other characteristics like age and titer value, the measure of antibodies present in blood. Complicating matters more, titer values don’t tell the whole story. A new infection should have a high titer value declining over time in response to treatment, but that’s not always the case. Some patients show no reduction in titer value one full year following treatment despite clearing the infection. Consequently, health departments have to investigate every case, a task that is enormously time-consuming.

To help the health departments identify and treat new, active cases earlier, Tigran Avoundjian, a PhD student in the Department of Epidemiology at the University of Washington’s School of Public Health, developed and tested a web-based app called the Syphilis Reactor Grid Evaluator (SRGE). The results from his study were published in the journal Sexually Transmitted Diseases.

SRGE builds on an existing reactor grid system used by health departments, but has never been digitized before. Since titers are not specific for new cases and health departments have limited resources to investigate each person, they often use a reactor grid to prioritize which cases to investigate. The reactor grid is essentially an algorithm to determine which combination of titer values and age yield the highest number of cases. While a reactor grid speeds up the investigation process, many health departments have trouble constructing the grid manually and making determinations, which slows down the staging process.

Syphilis is most contagious in its early stages, and symptoms come and go as the infection moves in and out of dormant phases. Facilitating timely treatment of the STI, which can cause a number of health problems including blindness, hearing loss, infertility, and neurological problems, is crucial to controlling its further spread. It can be treated with antibiotics, but an easy and quick diagnosis has been the biggest hurdle.

“At any given time, a state health department could have hundreds of open cases to be investigated,” Avoundjian said.

With this new app, a health department simply loads its data into the tool and can then interactively visualize where most new cases occur. For example, based on the grid results, a health department might decide that a woman of childbearing age with a high titer value should be investigated while someone over 60 with a low titer value should not.

SRGE also computes the impact of closing laboratory results without investigation. A user can easily click through the grid to see a hypothetical scenario: if cases with low titer values and patients aged over 45 were not investigated, how would that impact efficiency and how many cases would be lost? In King County, Avoundjian found that in using SRGE to prioritize cases, the health department could gain about 25% efficiency, which would reduce case investigations by more than 3,000 lab reports, with only 10 to 99 fewer true cases investigated.

”We have room to close more lab reports without sacrificing much in the way of case findings,” Avoundjian said.

Avoundjian has high hopes that the tool will be utilized elsewhere in the U.S. Already, health departments in Georgia, North Carolina, Texas, Illinois (Chicago only) and California have started to use SRGE to evaluate their reactor grids. Avoundjian has plans underway to present the tool to more health departments across the nation in the coming months.

“I wanted to develop a tool that would help health departments improve efficiency and open up time for other tasks,” he says. “If this tool can do that, I would consider it a success.”