Highly sensitive troponin I assay helps determine diagnosis of MI
MedWire News: Use of a highly sensitive test for troponin I levels could help determine the diagnosis of myocardial infarction (MI) within a few hours of admission for chest pain, a study has found.
Application of the relative change in highly sensitive troponin I (hsTnI) or cardiac troponin I (cTnI) concentration within 3 hours after admission in combination with the contemporary 99th percentile diagnostic cutoff value on admission improves specificity and may facilitate an early rule-in of MI, write Till Keller (University Heart Center, Hamburg, Germany) and colleagues.
They compared the diagnostic performance of a hsTnI assay with a contemporary cTnI assay, and their serial changes, in the diagnosis of MI among 1818 patients with suspected acute coronary syndrome. All patients were consecutively enrolled at chest pain units between 2007 and 2008.
The researchers measured 12 biomarkers, including hsTnI (level of detection 3.4 pg/mL) and cTnI (level of detection 10 pg/mL) on admission and 3 and 6 hours thereafter.
Overall, 413 (22.7%) patients were diagnosed with MI, defined according to current guidelines using evidence of myocardial necrosis consistent with myocardial ischemia, electrocardiography, or coronary angiogram. A final discharge diagnosis was based on conventional serial troponin measurements.
hsTnI provided the highest diagnostic information of the 12 biomarkers, with an area under the receiver operating characteristic curve (AUC) of 0.962, followed by cTnI, which had an AUC of 0.921 (p<0.001).
The use of hsTnI at admission, with the diagnostic cutoff value at the 99th percentile of 30 pg/mL, had a sensitivity of 82.3% and a negative predictive value (NPV) for ruling out MI of 94.7%.
On the other hand, the use of cTnI at admission, with the diagnostic cutoff value at the 99th percentile of 32 pg/mL, had a sensitivity of 79.4% and an NPV of 94.0%.
The use of hsTnI and cTnI obtained at 3 hours after admission yielded the same sensitivities, at 98.2%, and NPVs, at 99.4%.
After combining the 99th percentile cutoff at admission with the serial change in troponin concentration within 3 hours, the positive predictive value (PPV) for ruling in MI for hsTnI increased from 75.1% at admission to 95.8% after 3 hours, and for cTnI increased from 80.9% at admission to 96.1% after 3 hours.
"The relative change in concentration of hsTnI within 3 hours after admission in addition to the 99th percentile diagnostic cutoff provides a substantially improved PPV for the diagnosis of MI when compared with hsTnI determination on admission alone," conclude the authors.
By Piriya Mahendra