The Cardiac Troponins: Then and Now (Part One)
When I started working in a community hospital in the mid 1960s, we measured LD(H), AST (a.k.a. SGOT) and ALT (a.k.a. SGPT) in patients suspected of an acute myocardial infarction (MI). This was really all we had to assist the physician in making a diagnosis and treating the patient. Perhaps at that time those tests were sufficient for the treatment was mostly palliative-we did not have interventional therapy of any sort; no stents, no emergency by-passes, etc. Since then the treatment options have improved to where the laboratory is asked to report test results within 60 minutes or less (It doesn't hurt to keep in mind that the physician has been seeing ECG readings in less than that for some years.) It was no longer sufficient to use markers that did not rise for 4 to 8 hours after an event.
We are fortunate in the laboratory to have assays for cardiac troponin I and T (cTn) that can be performed on a sample (whole blood, serum or plasma) in 10 to 20 minutes. This has been a boon to many ED clinicians, especially in those MI patients whose ECGs are not diagnostic-as many as 50 percent. These assays are utilized in two versions, which for the sake of our discussion I will term simply laboratory-based (lab), and near patient (POC). Just having mentioned POC has raised the hackles on many of you, perhaps for good reason. I have often shied away from the discussion of where cTn testing should be done. However, I recently had the opportunity to listen to an ED physician described 10 years (sic) experience with cTn testing in his ED (POC). His busy ED is in a mid-sized community hospital. The nurses perform the test just as they have been doing ECGs for decades. There was reluctance when the project began but the entire staff soon saw the benefit in terms or early treatment for the patient with an MI (perhaps as low as 10 percent of patients in an ED with chest pain). Those without MI could be more rapidly triaged home or to a less intense bed. This laboratory has shown improvement not only in turn around times, a reduced length of stay in the ED, but a cost savings for the hospital. Having cTn available rapidly in the ED allowed the clinician and the nurses to be more effective as the assay allowed them to allocate their time better. As you can easily infer, my thinking on the question of where to test for cTn has changed.