Cardiology Corner: High Sensitivity Troponins
Anand Swaminathan, MD and Amal Mattu, MD
Print Editor: Whitney Johnson, MD, MS
- High sensitivity troponins can be used with a shortened duration of time between repeat tests.
- Approximately 2% of normal patients in the general population will have detectable troponin above the limit.
- Delta troponins are important to evaluate if the troponin level is in the gray zone.
- We have been talking about high sensitivity troponins for some time. Although the FDA approved the high sensitivity troponin for use in the U.S. in 2016, we are seeing increasing use over the last 6 months.
- Mattu does not have the high sensitivity troponin at his facility at this time; although, he anticipates they will get it in the future.
- Januzzi, JL Jr et al. Recommendations for institutions transitioning to high-sensitivity troponin testing: JACC scientific expert panel. J Am Coll Cardiol. 2019 Mar 12;73(9):1059-1077.PMID: 30798981
- Baugh, CW et al. Implementation of an emergency department high-sensitivity troponin chest pain pathway in the United States. Crit Pathw Cardiol. 2019 Mar; 18(1):1-4.DOI: 10.1097/HPC.0000000000000164
- What makes it a high sensitivity assay? These have higher sensitivity than the conventional troponin. They also are detected earlier. These fifth generation troponins will detect measurable cardiac troponin concentrations in at least 50% of healthy individuals. About 2% of normal patients in the general population will be found to have detectable troponin above the 99% percentile upper limit. In ED patients with chest pain who have cardiac comorbidities, it is likely more than 2%. As the sensitivity rises, the specificity falls.
- What is a positive highly sensitive troponin? Positive is greater than 52 ng/L. There may be some variations depending on the lab and assay used. Negative levels are more confusing. If the level is undetectable or less than 6 ng/L and the patient has been having chest pain for more than 3 hours, it is normal. If the chest pain has been present for less than 3 hours and the level is less than 6 ng/L, you cannot rely on a single value and will need to get a repeat test. There is a large gray zone.
- These assays are more likely to detect low levels of troponin and false positives are more likely. How can we incorporate this into our assessment of the patient? There are a lot of conditions other than acute coronary syndrome (ACS) that can cause detectable troponin levels such as tachy and brady dysrhythmias, dissection, severe congestive heart failure (CHF), sepsis (or anything that causes myocardial dysfunction), acute heart failure and chronic kidney disease (CKD). Serial troponins are important in this situation.
- A patient has chest pain and ACS is possible. The ECG is non-ischemic. The first high sensitivity troponin is negative. The patient has had chest pain for 4 hours. Do you need to do any additional testing or are you done?
- The JACC article describes several algorithms. These are well-researched and vetted.
- If the patient’s chest pain has been going on for more than 3 hours and a single troponin is less than 6 ng/L with a low HEART score, you are done. You still need to consider the ECG and history. You could also use another validated scoring system.
- If the chest pain is less than 3 hours in duration, they recommend obtaining a repeat troponin in 1 hour. In 2017, we discussed ACEP’s clinical policy on low risk chest pain. They recommended a 2 hour repeat highly sensitive troponin. There is now enough literature to say that if you are using a highly sensitive troponin, you can knock the time until repeat troponin down to 1 hour.
- If the patient presents after a half hour of chest pain and has a repeat troponin in an hour, is this sufficient or do you need to wait 3 hours after onset of symptoms? This scenario was not specifically addressed in the algorithms. However, there is sufficient support in the literature and published algorithm for a repeat high sensitivity troponin in an hour.
- You have a patient with possible ACS. The ECG is non-ischemic. The first high sensitivity troponin is in the positive range at 52 ng/L?
- You can call to admit the patient for rule in.
- You have a patient with possible ACS. The ECG is non-ischemic. The first high sensitivity troponin taken 4 hours after onset of pain is in the gray zone 40 ng/mL.
- This is complicated. In the algorithms, if a repeat troponin has gone up by a certain amount, you are done. If the repeat troponin has gone up by more than that, you need to get a three-hour troponin and factor in the HEART score. This approach is sensible.
- In the new algorithms, you can do a quicker rule out for patients with a HEART score of 4-6 and send them home. In the previous HEART pathway, patients with a HEART score of 4-6 were admitted or observed.
- These pathways and algorithms are powerful. We can adopt this in our clinical care. They are already vetted and well-researched. They can aid in the creation of your own protocols.
- There are multiple conditions such as CKD and CHF that can result in chronically elevated troponin and this will be even more common with high sensitivity troponins. When the patient has a slightly elevated troponin and a story that is less concerning for ACS, we usually repeat the troponin. Is this the case with high sensitivity troponin? Yes. You are looking for increases in the troponin similar to other patients.
- Is there still a role for the conventional troponin? Once you have adopted the high sensitivity troponin, there is not a good reason to keep the conventional troponin around.
Recent Related Material
EM:RAP 2017 January - High Sensitivity Troponin FDA Approved
EMA 2020 March - A Randomized Trial of A 1-Hour Troponin
EMA 2019 July - Ten Commandments for the 4th Universal Definition of MI