Interpretation of troponin that is "within normal limits" but greater than 2
I am an intern.
At my hospital the normal range for troponin is <12.
The lowest number the lab will report is "<2". If the lab reports a trop as "<2" then seniors talk about it as a "negative trop". Having had a look at the commercially available high sensitivity trop tests I have surmised that essentially most will report an undetectable trop as <2 (https://ifccfiles.com/2024/03/High-Sensitivity-Cardiac-Troponin-I-and-T-Assay-Analytical-Characteristics-Designated-By-Manufacturer-v062024.pdf).
If the lab reports a trop as 2-12 (e.g. trop of 11) then seniors talk about it somewhat inconsistently. Some seniors say it is elevated, others say it is elevated but normal, some say it is elevated but should be repeated, some have even said it is negative. Some seniors have told me that if someone had a trop of 6 then it would be incorrect to say it is negative.
If the lab reports a trop as 13 or more then seniors consistently talk about it as elevated.
Some months ago I saw a young women of approx 30 years of age in ED who I thought had a LRTI causing CP (details changed to deidentify patient). I did a trop which was reported as 10. The FACEM then told me that since the trop was elevated and the patient had some shortness of breath, we should proceed to a CPTA and do a repeat trop 3 hours after the first. The CTPA did not demonstrate a PE (and did show a LRTI for what its worth), and the repeat trop was also 11. The FACEM said since the repeat trop was 11 (i.e. repeat trop stable) this was not concerning.
I am left somewhat confused about the interpretation of troponins that are "within normal limits" but greater than 2. What is the best way to refer to these results ("negative trop", "elevated trop" etc)? Should all troponins between 2 and 12 be considered clinically concerning and be repeated at 3hrs? If that is the case, what it the point of even defining a normal limit for trop - shouldn't it just be undetectable (<2) or positive?
I have tried asking seniors in ED and have got mixed answers that are quite unsatisfying.
(yes I concede I am thinking about this more than is clinically relevant)