Alexander Limkakeng, Jr., MD, MHSc
Disclosure Relationship(s): Abbott Diagnostics: Research Grant; astra zeneca: Research Grant; Bristol Myers: Research Grant; GE: Research Grant; Ischemia Care, LTD: Research Grant; Roche Diagnostics: Research Grant; Siemens Healthcare Diagnostics : Research Grant
Background: High-sensitivity cardiac troponin (hs-cTn) assays aid in diagnosis of acute myocardial infarction (AMI), but have lower specificity in patients with renal disease. Our objective was to define an optimal 1-hour delta hs-cTnI for patients with renal disease.
Methods: We conducted an a priori secondary analysis of a prospective FDA 510k study in adults with suspected AMI presenting to 29 academic urban emergency departments (EDs) between 11/2014 and 12/2015. We excluded patients who had recent MI, or in whom we could not obtain sufficient blood samples. Blood samples were collected at time 0, 1, 3, and 6-9 hours. We recorded electrocardiogram, radiography, cTn, and stress test results, and estimated glomerular filtrate rate (eGFR) by Modified Diet in Renal Disease (MDRD) equation. The primary endpoint was AMI, as adjudicated by blinded independent physicians per the 3rd Universal Definition of MI. Separate Receiver Operator Characteristic (ROC) curves of absolute 1-hour delta hs-cTnI (Siemens Atellica LiHep plasma hs assay, Limit of Detection = 6 ng/L) were generated for patients with eGFR >60, 31-60, 15-30.
Results: 2505 subjects were enrolled; 481 subjects were excluded from analysis due to missing creatinine or cTnI values or recent MI. The median age was 56 years (interquartile range (IQR): 48.0, 65.0). Patients were mostly male (1374, (56.6%)) and white (1377 (56.4%), 478 (19.7%) had a past MI, and 1920 (79.0%) had an eGFR >60 mL/min/1.73 m². The median (IQR) time from symptom onset to presentation was 5.7 (2.0, 26.4) hours. For all patients, absolute 1-hour delta of 2 ng/L had sensitivity and specificity of 73.2% and 90.8% (c statistic=0.77), respectively. An analysis of only patients with baseline hs-cTnI between 6-120 ng/L (n=899) showed that an absolute 1-hour delta of 2 ng/L had 71.8% sensitivity and 84.8% specificity (c=0.81). For patients with baseline hs-cTnI between 6-120 and eGFR of >60, 31-60, 15-30 and < 15 mL/min/1.73 m2, optimal 1-hour delta cutoffs (sensitivity, specificity) were 2 ng/L (76.0%,85.0%), 1 ng/L (71.4%,74.8%), 8 ng/L (100%,94.4%) and 5 ng/L (60%,88.9%) respectively.
Conclusions: A simple eGFR-adjusted one-hour delta threshold for the Siemens Atellica hs-cTnI identifies AMI in patients with renal disease with high sensitivity and specificity. These findings suggest potential 1-hour delta cutoffs to use in such patients.