September 28th, 2011
Study Finds Noncardiac Sources of Positive Troponin T Tests
Cardiac troponin T (cTnT) is not always cardiac specific and in some cases may lead to a false-positive diagnosis of cardiac injury, according to a study in the Journal of the American College of Cardiology.
The study was prompted by a case seen by a senior clinician at the Mayo Clinic in which a patient, who was ultimately found to have a form of muscular dystrophy and no heart disease, had persistent cTnT elevations despite a slew of other negative tests, including negative cardiac troponin I (cTnI). Allan Jaffe and colleagues then sought to find similar myopathy patients treated at the Mayo Clinic’s Neuromuscular Clinic by measuring both cTnT and cTnI.
The authors identified 16 myopathy patients without cardiovascular disease who had increased cTnT but not cTnI. A Western blot analysis demonstrated that skeletal muscle proteins were capable of provoking a positive cTnT response.
In their discussion, the authors acknowledge that the clinical significance of this problem is not known, but “it appears likely that there are at least some circumstances in which increases appear to be due to noncardiac sources of cTnT, and these certainly could lead to confusion in individual clinical cases.” Previous studies further suggest “that the frequency of such clinically undetected myopathies may not be trivial.” The authors note that “even if the frequency of false-positive increases is extremely low, given the large numbers of patients evaluated with this testing, the absolute numbers of patients who could have increases due to skeletal muscle disease could be substantial.”
For an expert’s take on the findings, see the latest post from CardioExchange’s James de Lemos here.