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Saturday, March 26, 2011

More Sensitive Troponin 1 Assay to Screen for Possible Heart Attack in Future

Posted by Prahallad Panda on 7:06 AM Comments

typical changes in CK-MB and cardiac troponin ...Typical Changes in CK-MB and Cardiac Troponin In MI
Currently, troponin is measured on admission and 12 hours after the onset of symptoms of heart attack as recommended in the UK. However,
Troponin levels actually rise quickly after an MI but may not reach higher thresholds until six to 12 hours after symptom onset. The cut off level to diagnose myocardial infarction at present is more than 0.20ng/ml of plasma.
More sensitive troponin assay can detect levels as low as 0.05ng/ml of plasma. Symptomatic patients having level between 0.05ng/ml and 0.20ng/ml frequently had heart attack within following 12 months; observed by the researchers. But they are being conveniently reassured not to have myocardial infarction(MI) at that time; but may have high risk of another MI within following 12 months.
In the new study, published in the March 23/30, 2011 issue of the Journal of the American Medical Association, the researchers found that the introduction of the more sensitive assay to the clinic led to a halving in death/MI at 12 months in patients who had troponin levels between 0.05 and 0.20 ng/ml.
These more sensitive troponin tests have been available since 2008 and are more widely used in Europe than in the US. By lowering the diagnostic threshold, more patients will be referred to specialists and be investigated. Interestingly, the researchers identified only one patient in a study who was given an inappropriate diagnosis of acute coronary syndrome after the sensitive assay was introduced, and she turned out to have a pulmonary embolism. So false positive diagnosis is not an alarming problem.
False positives could be more of a problem with the new assays, if they were used inappropriately as a screening test in patients who don't have chest pain. This needs to be discouraged. But the study shown that in patients with chest pain, there is little doubt that sensitive troponin tests will improve diagnostic accuracy and outcomes.
From the enrolled 2092 patients with chest pain, 1340 (64%) had plasma troponin assay concentrations of less than 0.05 ng/mL, 170 (8%) had levels of 0.05 to 0.19 ng/ml, and 582 (28%) had levels of 0.20 ng/ml or more.
During the validation phase, at 12 months, a greater proportion of patients with troponin assay concentrations of 0.05 to 0.19 ng/ml had died or been re-admitted with an MI compared with those with troponin levels less than 0.05 ng/ml or 0.20 ng/ml or more; the study concludes.
During the implementation phase, lowering the diagnostic threshold to 0.05 ng/ml was associated with a lower risk of death and recurrent MI in patients with troponin concentrations of 0.05 to 0.19 ng/ml--from 39% to 21%; the study says.
This study was conducted by Dr Nicholas Mills (British Heart Foundation Centre for Cardiovascular Science, University of Edinburgh, Scotland).
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