Vigorous Exercise Can Throw Off Lab Test Results

Rarely, someone who has undertaken a prolonged strenuous activity – like running a marathon – may faint and be taken to the ER. Once there, he (or she) may have a blood test designed to detect a heart attack: a serum troponin level. Troponin is a protein that is released from heart muscle when it’s damaged, as in a heart attack. Around 2001 the American College of Cardiology and the European Society of Cardiology recommended that a raised level of troponin was a required diagnostic feature of a heart attack (a myocardial infarction, or MI).

In 2002, London Hospital physicians conducted a study in 34 marathon runners, and published their findings in the British Journal of Sports Medicine. The contestants had blood taken before and after the race. The results showed significant increases in creatine kinase, aspartate aminotransferase, lactate dehydrogenase, and myoglobin after the marathon. But there was no change in the serum troponin levels. The authors of the report concluded: “The results of investigations inpatients who have been exercising should be interpreted with caution”.

In a review published in Sports Medicine shows that numerous publications support a transient but significant elevation in troponin levels after strenuous exercise, without actual cardiac damage. It’s clear that other criteria should be employed in the diagnosis of a heart attack in people who have just completed vigorous exercise.