[Extract] To be clinically useful, diagnostic tests need high precision. The original troponin assays had poor precision: they had high variability, particularly at the level used to determine whether a myocardial infarction (MI) was present. To address this problem, high-sensitivity troponin (hs Tn) assays were developed, the sensitivity referring not to the tests’ diagnostic sensitivity, but the analytic sensitivity with lower limits of detection and greater precision, including at the upper reference limit used to determine the presence of MI. This makes hs Tn more useful for ruling out MI and acute coronary syndrome in patients presenting with acute chest pain, allowing a greater proportion of patients to be discharged home earlier and potentially reducing the sex bias in the diagnosis of MI. These assays have been in use in Europe and Australasia since about 2010 but have only recently been approved by the Food and Drug Administration for clinical use in the United States.