(Aotea News, June 2011)
These case studies relate to the article The merits of high sensitivity Troponin T in primary care.
A 63-year-old man with a 10 year history of type 2 diabetes
The patient has a dizzy spell while mowing his lawn. Hypoglycaemia is not an issue and he recovers quickly after resting but he is sufficiently worried to come to you the next morning.
There are no clinical findings but there seems to be a possibility of a silent infarct so you request high sensitivity troponin T in a specimen taken 18 hours after the event. The result is 6ng/L.
Interpretation
This result is well under the 99th centile and, given the time since the symptoms, rules out myocardial infarction.
A 75-year-old patient with atrial fibrillation and mild congestive heart failure
A patient has an episode of minor chest discomfort overnight and has become slightly more breathless than usual, but is not seriously distressed.
High sensitivity Troponin T about 12 hours after the pain is 52ng/L.
You are surprised and worried by this result as you had considered myocardial infarction to be unlikely and were hoping for confirmation through a normal result.
With some difficulty you persuade the cardiology registrar to review the patient at A&E. Repeat troponin at 18 hours is 50ng/L.
The patient is kept overnight and a further specimen at 24 hours is again 52ng/L.
Interpretation
The stable pattern of abnormal results does not support myocardial infarction but is quite typical in patients with tachycardias or heart failure, even when there has not been clinical deterioration.
The difficulty for you is in assessing the significance of the first result and deciding whether to refer or manage yourself.
The latter course requires you to seriously consider repeat testing for troponin as the first result has not allowed you to rule in or rule out myocardial infarction.
A question to consider might be whether it would influence your decision if the first result in this patient had been 26 rather than 52.