The Immunoassay-Mass Spec Balancing Act

When bringing a new tests into the lab, the question of which testing methodology is best to apply can be challenging. This is especially true with antiepileptic drugs (AED), such as levetiracetam, lamotrigine, gabapentin, lacosamide, topiramate, oxcarbazepine, and zonisamide.

 With limited resources available, you may look to any available literature or ask a colleague. However, in the session “To Immunoassay or To Mass Spec: Lab Stewardship Questions When Bringing Antiepileptic Drug Assays In-House,” speakers gave specific guidance on how to choose the appropriate AED testing methodology for any clinical lab.

“The choice between mass spectrometry and immunoassays as it concerns bringing antiepileptic drug testing in house is not black and white,” said speaker Adina Badea, PhD. “The idea that one is better than the other in all situations is a false dichotomy.”

The session highlighted three different AED projects that touched on the decision to bring testing from send-out to in-house and which methodology—immunoassay or mass spectrometry—would be best for their individual clinical setting or patient population.

All the panelists went through the factors that influenced their choices, with the goal of helping the audience inform similar decisions at their home institutions. They touched on four main factors that drove their decision-making, including analytical, cultural, financial, and logistical considerations.

Claire Knezevic, PhD, kicked off the session with a discussion of how to maximize the clinical value of low-volume immunoassay testing. She recommended using immunoassays for AEDs because testing can be integrated into the lab’s automated system with auto-verification, leading to a short turnaround time (TAT). However, she warned that immunoassays can be affected by analytical interferences and limited instrument availability and capacity.

Next Alec Saitman, PhD, described the process and factors that motivated switching from immunoassays to mass spectrometry for AED testing. He underscored advantages of mass spectrometry testing, including multiplexing of several AEDs on one assay. This leads to eliminating multiple immunoassays, one for each AED, and the ability to run lower volume AEDs as they are run alongside other AEDs on the same assay. However, he stressed the importance of understanding each lab’s logistical factors and comfort in using mass spectrometry.

Badea showed the steps to assessing true clinical need for AEDs and TAT constraints, as TAT affects the decision between immunoassay or mass spectrometry testing. She recommended using patient data to assess the true clinical needs of the tests. By understanding why the test is being ordered and how clinicians are using the results to treat the patient, she was able to see what kind of TAT was needed.

In the end, with the increase in use of AEDs, analytes that used to be good candidates for a mass spectrometry assay are reaching demand volumes that make the now widely available immunoassays a competitive alternative.

The speakers predicted that more institutions would benefit from bringing AED testing in-house. Although there is no right answer between immunoassay and mass spectrometry, knowing the pros and cons of each methodology for specific clinical settings will be useful to any institution embarking on this decision-making process.