Analytical Concordance of Diverse Point-of-Care and Central Laboratory Troponin I Assays Albert K.Y. Tsui, 1,2* Martha E. Lyon, 3 Sean van Diepen, 4 Bobbi Lynn Goudreau, 2 Dylan Thomas, 1,5 Trefor Higgins, 1,5 Joshua E. Raizman, 1,2 Anna K. Füzéry, 1,2 Karina Rodriguez-Capote, 1,5 Mathew Estey, 1,5 and George Cembrowski 1,2 Background: Cardiac troponin I (cTnI) 99th percentile cutoffs, used in the diagnosis of acute myocar- dial infarction, are not standardized across cTnI assays. We compared 3 point-of-care (POC) and 1 central laboratory contemporary cTnI assays against the Abbott high-sensitivity (hs) cTnI to evaluate the analytical concordance and the feasibility of using a single cutoff value for all assays. Methods: Fresh blood samples collected from 102 inpatients in the coronary care unit were measured on central laboratory instruments (Beckman Coulter DxI AccuTnI+3 TnI, Abbott Architect hs-TnI) and cTnI POC analyzers (Alere Triage Troponin I, Radiometer AQT90, Abbott i-STAT). Agreement and corre- lation between the contemporary cTnI assays and hs-cTnI assay were assessed using regression anal- ysis. Proportional bias was assessed using Bland–Altman plots. Concordance between the contemporary cTnI and hs-cTnI assays was determined by diagnostic contingency tables at specific cutoffs. Results: Most POC cTnI assays had excellent correlation with the Abbott hs-cTnI method (r 2 = 0.955– 0.970) except for Alere Triage (r 2 = 0.617), while proportional bias is evident between all cTnI assays. Overall concordance between POC contemporary cTnI assays and hs-cTnI assay was 80% to 90% at their respective 99th percentile cutoffs. The concordance increased to 90% to 95% when a fixed cutoff of 0.03 to 0.05 ng/mL was used across the assays. Conclusions: This study demonstrates poor analytical concordance between cTnI assays at the 99th percentile and supports the notion of a single clinical decision limit for cTnI and consequently stan- dardization of diagnostic protocols despite the analytical differences among these assays. IMPACT STATEMENT This study compares the analytical concordance of 3 point-of-care (POC) and 1 contemporary central laboratory cardiac troponin I (cTnI) assays to a high-sensitivity cTnI assay using the 99th percentile and an alternative cutoff. These data can be used as an approach to harmonize troponin interpretation when 2 different troponin systems coexist. The evidence of the study will help laboratories decide on an optimized threshold with improved analytical concordance for the pair of POC and central laboratory troponin assays. 1 Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB, Canada; 2 Department of Laboratory Medicine and Pathology, Alberta Health Services, Edmonton, AB, Canada; 3 Department of Pathology and Laboratory Medicine, Saskatoon Health Region, ARTICLES 764 JALM | 764 –774 | 03:05 | March 2019 ....................................................................................................... Downloaded from https://academic.oup.com/jalm/article/3/5/764/5603111 by guest on 05 June 2022