Saliva-based rapid test for heart attack feasible
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Using a novel saliva-based rapid cardiac troponin I test to diagnose MI was feasible, according to the results of a preliminary study presented at the European Society of Cardiology Congress.
The test requires patients to spit into a tube and can return results in approximately 10 minutes compared with 1 hour or more for blood tests, according to a press release from the ESC.
“There is a great need for a simple and rapid troponin test for patients with chest pain in the prehospital setting,” Roi Westreich, MD, from the department of cardiology, Soroka Medical Center, Ben-Gurion University of the Negev, Beer-Sheva, Israel, said in the release. “Currently troponin testing uses blood samples. In this preliminary study we evaluated the feasibility of a novel method using saliva.”
Westreich and colleagues collected saliva samples from 32 patients with myocardial injury confirmed by a cardiac troponin T blood test and from 13 healthy volunteers. They processed the saliva samples for 25 patients with myocardial injury and nine healthy volunteers. All participants also underwent a new cardiac troponin I blood test.
“It is important to emphasize that the great importance in developing a saliva-based troponin test is not only the speed of the test but also its availability,” Westreich told Healio. “The test can be performed anywhere and not only in hospitals or emergency rooms.”
According to an abstract, the samples tested underwent the following processing procedures (SHAPED, Salignostics): amplification buffer to remove a broad spectrum of saliva; hampering remover to extract salivary alpha amylase and increase detection sensitivity; and saliva concentrator cartridge, which allows rapid concentration of analytes. Two investigators evaluated all results independently.
Of the 25 patients with myocardial injury whose samples had advanced processing, 21 were confirmed positive for MI by both investigators (sensitivity, 84%), and all four with negative results had blood cardiac troponin T levels of 155 ng/L or less.
There were no false positives in the processed or unprocessed samples of the healthy volunteers (specificity for both, 100%), Westreich and colleagues wrote in the abstract.
“This early work shows the presence of cardiac troponin in the saliva of patients with myocardial injury,” Westreich said in the release. “Further research is needed to determine how long troponin stays in the saliva after a heart attack. In addition, we need to know how many patients would erroneously be diagnosed with heart attack and how many cases would be missed.”
The next steps are to test a larger group of patients and to develop a prototype that “will be tailor-made for processed saliva and is expected to be more accurate than using a blood test on saliva,” Westreich said in the release. “It will be calibrated to show positive results when saliva troponin levels are higher than a certain threshold and show a yes/no result like a pregnancy test.”
Perspective
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This is not a test that should be made available to the general public. This is not the same as a pregnancy test, where you are pregnant or you are not. A large number of patients with elevated troponin are not having MI. There must also be clinical evidence of ischemia. People with advanced HF, advanced renal failure or recent trauma are among those who have elevated troponin levels but not MI. Many of these cases are myocardial injuries and not MI. Elevated troponin means the heart has been involved in some disease process, but it could be an innocent bystander. We see this in patients with COVID-19, who have myocardial injury from the SARS-CoV-2 virus itself or from the immune response to it that occurs in some people. None of those are MIs. Making a saliva-based troponin test available to the public would cause a lot of unnecessary visits to the doctor’s office or the ED.
The saliva-based test could be helpful in the ED if it were as accurate as the high-sensitivity troponin blood tests that come back in a couple of hours. It might be useful as a screening test in smaller community hospitals that do not have the high-sensitivity troponin blood tests.
I would like to see these results replicated in 1,000 patients, some known to be positive and some known to be negative through blood tests, to see if these numbers hold. If they do, then certain ED settings may benefit from it, though probably not the major centers that are already set up for rapid diagnosis and response. It must remain in the hands of medical professionals who understand that not every case of elevated troponin is an MI.
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Westreich R, et al. Abstract 85437. Presented at: European Society of Cardiology Congress; Aug. 29-Sept. 1, 2020 (virtual meeting).
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