Serum troponin is now the standard marker of cardiac muscle injury. Which of the following is a correct statement about the cardiac marker troponin when a patient's symptoms suggest an acute coronary syndrome?
A single normal reading rules out a cardiac cause.
A single normal reading rules out pulmonary embolism.
Serial measurements of troponin are needed to confirm a cardiac cause.
Stress imaging tests must be done after troponin levels are measured.
