Highly sensitive troponin T assay predicts cardiac risk in healthy patients

The results of a highly sensitive assay for cardiac troponin T (cTnT) can predict cardiovascular events in apparently healthy populations, according to new research.

As part of the Dallas Heart Study, cTnT levels were measured using both standard and highly sensitive assays in more than 3,500 patients ages 30 to 65. The standard assay found detectable cTnT in only 0.7% of the study participants, while the highly sensitive test found it in 25%. The results were published in the Dec. 8 Journal of the American Medical Association.

The researchers stratified participants based on their cTnT levels (according to the highly sensitive test) and compared their mortality rates as well as cardiac structure and function measured by MRI. Only 7.5% of people in the lowest cTnT group had left ventricular hypertrophy compared to 48.1% in the highest cTnT group. Mortality also increased from 1.9% in the lowest group to 28.4% in the highest. After adjusting for traditional cardiac risk factors, the study found that cTnT was independently associated with all-cause mortality (adjusted hazard ratio, 2.8 in the highest cTnT group).

Another study in the same issue tested the highly sensitive cTnT assay's ability to predict heart failure in more than 4,000 community-dwelling elderly patients. The biomarker was detectable in the majority of patients (66.2%) and associated with an increased risk of heart failure and cardiovascular death at higher concentrations (4.8 deaths per 100 in highest group compared to 1.1 in patients with undetectable levels). This study continued cTnT measurements over time and found that increases of more than 50% were also associated with cardiovascular events.

The results indicate that the highly sensitive cTnT assay has potential clinical utility, especially given its success at predicting mortality in patients who would be considered low risk according to the Framingham score (which is based on sex, age, cholesterol, blood pressure and diabetes and smoking status), concluded the authors of the first study. In both studies, there was significant overlap between cTnT and N-terminal pro-brain-type natriuretic peptide, suggesting that more accurate predictions may be achieved by use of both tests together. However, appropriate therapeutic responses to cTnT results will have to be established before the highly sensitive tests can be recommended for widespread screening, the researchers advised.

The authors of the first study also warned about the potential effects of the highly sensitive test if it is used in the hospital for diagnosis of acute myocardial infarction: Diagnostic sensitivity would be improved, but specificity would decline, potentially leading to false-positive diagnoses and unnecessary treatment.