Saliva Troponin Test for MI Has 'Huge Potential,' But Still Early

Dr Roi Westreich

Preliminary results with a point-of-care test developed to assess cardiac troponin I (cTnI) in saliva rather than blood have shown cTnl can be detected in the saliva of patients with proven myocardial injury.

The small feasibility study included 41 patients and 66 control participants who had a saliva test for cTnI developed by Salignostics (Jerusalem, Israel). The results were presented at the European Society of Cardiology (ESC) Congress 2020.

Test results could be obtained within 10 minutes, compared to 1 hour for the standard blood troponin test, Roi Westreich, MD, from Soroka University Medical Centre, Beer Sheva, Israel, and colleagues report.

However, further research is needed in a larger sample "to determine how long troponin stays in the saliva after a heart attack," and "how many patients would erroneously be diagnosed with heart attack and how many cases would be missed," Westreich acknowledged in a press release issued by the ESC.

"We wish to develop an option of early, initial diagnosis out of the hospital, in community clinics, remote small hospitals, ambulances," and in patients' homes, Westreich told theheart.org | Medscape Cardiology in an email.

In these settings, he added, "the high accuracy of the high-sensitive cTn (hs-cTn) [laboratory] test is not a 'must have.' Rather, a high negative predictive value and sensitivity are good parameters for evaluating the test performances."

'Interesting' But 'Very Preliminary'

"This study is small in numbers and has limitations; however, it is a very interesting and important one," Roxana Mehran, MD, Mount Sinai Hospital, New York City, who was not involved in the research, told theheart.org | Medscape Cardiology.

"Imagine if we can diagnose heart attacks at home with a saliva test how much more effective we can be in improving health outcomes of patients," she said.

"The potential is huge, but we are in the early stages, and this study only shows the feasibility and possibilities for the future," Mehran added.

Similarly, Nicholas L. Mills, MD, PhD, University of Edinburgh, Scotland, UK, who was also not involved with the research, told theheart.org | Medscape Cardiology that "this is an interesting innovation in cardiac troponin testing, but I would caution that the findings are very preliminary."

The point-of-care assay used in the current study has a very high detection threshold, he pointed out.

However, Mills agrees that "it is great to see innovation in cardiac biomarker testing and, in particular, approaches to testing that are less invasive for patients.

"A rapid saliva test to identify patients who clearly have substantial myocardial infarcts that could be performed in the ambulance could make a useful contribution to patient care by facilitating direct transfer to cardiac centers if it could match the performance of more contemporary point-of-care blood tests for cardiac troponin," he said.

An ECG should always be the first-line test in a patient with acute chest pain to establish whether immediate coronary reperfusion is required, Mills added. A rapid, sensitive, point-of-care troponin test combined with a 12-lead ECG and clinical assessment could permit clinical decisions to be made.

"Based on the performance reported here," Mills summarized, "salivary cardiac troponin testing merits further evaluation using more sensitive point-of-care platforms and in a larger more representative patient population."

Promising Findings, Next Steps

The researchers analyzed saliva samples from 41 patients who had a positive hospital laboratory hs-cTnT blood test and from 66 healthy controls.

The saliva samples were treated to remove alpha amylase, the most common protein in saliva, and then analyzed in using the Troponin I Serum Rapid Test (Diagnostic Automation/Cortez Diagnostics, Woodland Hills, California).

"Like the home pregnancy test, the analyzer used in this study is based on lateral flow immunoassay, in which a liquid sample laterally flows over a nitrocellulose membrane," Yoav Neumann, PhD, Salignostics, told theheart.org | Medscape Cardiology." Two lines are formed if a target molecule presents in the sample and only one line forms if it is not."

"We have found that patients who have had blood cTnT levels of 100 ng/L or lower tend to have negative saliva cTnI tests," he said.

Using a threshold of 100 ng/L to indicate a positive cTnI test, the sensitivity was 96.97% and specificity was 89.39%. The positive predictive value was 82.05% and the negative predictive value was 98.33%.

The false-positive rate was 10.6% (7 of 66 controls).

"Much needs to be done in this arena, and I look forward to this research going forward," said Mehran. "The validity of this test, its implication on accuracy of diagnosis, and impact on clinical outcomes are all yet to be determined."

The company is beginning a larger trial and has obtained consent from 200 patients and 200 healthy controls.

The study was funded by Salignostics, for which Westreich is a consultant and Neumann is an employee.

European Society of Cardiology (ESC) Congress 2020. Presented August 28, 2020.

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