Infectious Disease Serology: Are You Still Ordering That Test?

Infectious disease test serology is often confusing for both laboratorians and clinicians—which can negatively impact patient care and raise healthcare costs.

As laboratories are tasked with doing more testing without any increase in staff or resources, lab directors may be asked to oversee testing that falls outside their area of expertise. At the same time, clinicians are facing an abundance of testing options and must understand how to interpret unexpected results.

These trends can lead to the misuse and misinterpretation of serologic assays for infectious disease diagnoses. In today’s session, “Infectious Disease Serology: Are You Still Ordering That Test,” the speakers will share cases, illustrative experiences, and instructions on how to best approach infectious disease serology testing.

The first speaker, Patricia Slev, MD, PhD, DABCC, will briefly review the evolution of infectious-disease testing and provide an overview of the fundamental principles of serology testing for commonly encountered pathogens.

“Increasingly, infectious disease serology testing is available outside the traditional microbiology laboratory, creating a need for non-microbiologists to understand the benefits, challenges, and limitations of infectious disease serology,” says Slev.

Clinical assays and automation have improved over time, resulting in more test choices in different sections of the laboratory. As testing has evolved, some serology tests have become obsolete, but they are still frequently ordered. Slev will use the many options for Lyme disease testing as an example and offer advice on how to navigate the confusing diagnostic landscape.

Next, Elitza Theel, PhD, DABMM, will discuss the misuse and misinterpretation of serologic assays. As a laboratory director, she is frequently consulted on infectious-disease cases that involve excessive testing. She will relay approaches to optimize diagnostic testing, focusing on neurosyphilis as an example.

In her laboratory, specific assays were overused on patients who were not at risk for syphilis, never mind neuroinvasive infection. Using data from her Venereal Disease Research Laboratory (VDRL) test utilization study, she plans to implement a policy that requires patients to have a positive syphilis antibody blood-test result before any spinal-fluid test can be performed—a change that will significantly reduce unnecessary testing.

This approach is anticipated to improve patient care, lower healthcare costs, and aid clinicians in test selection.

Sarah Wheeler, PhD, FADLM, will wrap up the session by emphasizing the importance of stewardship when it comes to test utilization. She will describe the increasing availability of nucleic acid testing (NAT), which can complicate the decision of whether to use NAT or serology for diagnosis.

Wheeler will use a costly viral meningoencephalitis CSF serology panel frequently ordered at a pediatric center as an example of a test that, over the course of a year, provided no clinical utility. She will share her approaches to improve test utilization, including removing the ability to directly order specific tests.

Attendees will learn about over- or under-used assays for infectious disease diagnostic assays and how to guide clinicians on appropriate test selection. The experiences shared by the speakers will help laboratorians to implement changes in their own clinical settings.