Assessing the analytical performance of a point of care high-sensitivity troponin assay

Hi I’m Mike Samoszuk. I’m the Medical Officer for Siemens Healthineers, formerly the Chief Medical Officer at a number of global in vitro diagnostic companies.

Troponin testing has been used for a number of years now to help diagnose a heart attack or myocardial infarction in patients who present to the emergency room with chest pain or other symptoms suggestive of a heart attack. The test is an important part of making that diagnosis. It’s not the only part, but it’s probably the most important part. So, it’s essential that you get a correct answer, quickly, that the clinician can depend upon to make a decision.

Point of care testing for troponin yields the same result as the main laboratory but with an important caveat; although the results will be comparable analytically and clinically, they will not be identical numerically. And by that I mean that if the test is positive from the main lab the test should be positive and will be positive with the point of care device as well, and you can also rely upon the precision and linearity and accuracy of both devices, they will be comparable. However, the numerical results generated by the two instruments will be different and this has been known for a long time regardless of the manufacturer or the source of the assay, troponin results will vary from instrument to instrument and so you cannot compare the numbers, but the analytical interpretation, the precision, the linearity, the accuracy will be comparable or equivalent in both devices, point of care and main laboratory.

So, an important question is - when is the high sensitivity assay most useful? And there’s been a lot of confusion about that. You know, for a while it was thought that everybody needed to have a high sensitivity troponin assay. In reality, if a person has had a big heart attack or even a moderately large heart attack, even a conventional troponin assay can detect that and there’s really not a problem. The problem occurs at the margins, at the lower end, just at the borderline between normal and abnormal – that’s where you want to get precision, you want to get a reliable result. So, the most useful application for the hight sensitivity troponin assay is at that borderline region where there’s a marginal elevation and you’re trying to determine whether it’s significant and whether there’s a significant change over time. There’s not really a major problem when somebody has a massive heart attack with a massive elevation of troponin, any assay can detect that.

So, gender-specific reference ranges for troponin are important because, believe it or not, men and women are different in that regard. Men and women can present with different kinds of symptoms for cardiac ischemia and heart attacks. And in addition, men and women turn out to have different 99% cut-offs for what is a normal troponin level. So, for men that level is a little bit higher than for women. So, if you have a woman and who presents to the emergency room with some atypical symptoms that may or may not be a heart attack, it’s important to be able to interpret the test result for the troponin with gender-specific reference range because we expect that normally women have lower levels of troponin and so with the high sensitivity troponin you can detect a slight elevation and label it as being abnormal when it might not be considered abnormal in a man. So, the reference ranges are different, the cut-off points for making a determination of a heart attack are slightly different in men and women and a gender-specific reference range is essential for making that important diagnosis with accuracy at these lower levels of troponin elevation.

So, the main benefits of performing a high sensitivity troponin assay at the bedside are, I think, almost intuitively obvious. You get a fast result, you don’t have to wait for the result to come from the main laboratory which typically takes an hour, the assay can be performed on a small device that doesn’t take up a lot of room, it’s a simple device that’s easy to operate by a relatively untrained operator and it requires just a small sample of blood, so, just a fingerstick, which is easy to obtain. So, it’s a remarkable development to be able to get a fast, accurate result from a small sample, from a small device at the patient’s bedside – this is revolutionary.