In a study published this week in the Journal of the American Medical Association, scientists from the University of Edinburgh determined that use of more sensitive tests to detect the protein biomarker troponin could improve diagnosis and treatment of heart attacks.
The results, which indicated that lowering the standard diagnostic threshold for troponin to 0.05 ng per mL from 0.2 ng per mL increased detection of heart attacks by 29 percent, could bolster the case for more sensitive troponin assays like those being developed by biotech firms Singulex and Nanosphere (PM 12/17/2010).
Lowering the diagnostic threshold has "been a contentious issue for cardiologists for some time," said Nicholas Mills, a cardiologist at the University of Edinburgh and one of the authors of the study. The fear, he said, "is that the lower you bring the threshold down, the more likely you are to identify false positives."
False positives are "a real concern," Mills told ProteoMonitor, but the JAMA study suggests that the threshold for troponin could be lowered from its current level without decreasing the test's specificity. In the study, the researchers used Abbott Architect troponin 1 assays and, at the revised threshold of 0.05 ng per mL, generated only one false positive out of 2,092 patients. That subject later presented with a pulmonary embolism.
Singulex's troponin test, which is designed for use on its Erenna single-molecule immunoassay platform, can detect troponin levels in a range of approximately 1 to 10 picograms per mL, which, Mills said, is where troponin assays need to be to be used for general monitoring purposes. While the protein is often used in acute settings to diagnose heart attacks, it has been less useful for long-term monitoring because of the difficulty in measuring it at low enough concentrations to establish a baseline for normal subjects.
The cardiology community as a whole is "not yet ready" for such high-sensitivity assays, Mills said, but added that he sees "some real advantages to being able to" measure at those low levels, noting that recent studies suggest such tests could be useful for monitoring patients with stable coronary artery disease.
Such assays, however, are still "very far from being used in routine clinical practice for the assessment of stable patients," he said, suggesting that in the near term they'll primarily find use in "an experimental research setting."
In December, Singulex officials told ProteoMonitor that the company hopes to apply for US Food and Drug Administration approval of its troponin test within the next two years. On its full-year 2010 earnings call last month, Nanosphere officials said the company planned to file for FDA clearance of its troponin assay this summer and expects a product launch in the first part of 2012 (GWDN 2/17/2011).
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