High-sensitivity cardiac troponin (hs-cTn) assay was approved by the US Food and Drug Administration in 2017,1 and its appropriate use is currently being investigated. In this issue of JAMA Internal Medicine, Gallacher et al2 examine the use of hs-cTn assays in patients with kidney impairment in a prespecified secondary analysis of a randomized clinical trial of patients with suspected acute coronary syndrome (ACS). Their major finding is that while the frequency of elevated levels of hs-cTn increases as kidney function deteriorates, two-thirds of patients with kidney impairment and elevated hs-cTn concentrations do not have a type 1 myocardial infarction (MI related to coronary thrombosis). Despite the discovery of more patients with elevated troponin levels by hs-cTn assays, 1-year rates of a type 1 MI or type 4b MI (occurring ≤48 hours after percutaneous coronary intervention) or cardiovascular death were unchanged before and after implementation of hs-cTn testing in patients with and without kidney impairment.