Architect i1000sr

Blood samples were collected in both the ARISTOTLE and RE-LY studies in EDTA tubes at randomization and immediately centrifuged, frozen in aliquots, and stored at −70 °C until analysed centrally at the UCR Laboratory, Uppsala, Sweden. Cardiac troponin-I (cTnI-hs) levels were determined with high-sensitivity immunoassays on the ARCHITECT i1000SR (Abbott Diagnostics), Troponin-T (cTnT-hs) and N-terminal pro B-type natriuretic peptide (NT-proBNP) with high-sensitivity immunoassays on the Cobas^® Analytics e601 (Roche Diagnostics), growth differentiation factor-15 (GDF-15) with the Elecsys GDF-15 pre-commercial assay kit P03 with the same standardization as the recently introduced routine reagent (ROCHE Diagnostics). All analyses were performed according to the instructions of the manufacturer and have been detailed previously.¹³ (link)^,23–29 (link) Plasma creatinine (Roche Modular) and haemoglobin (Beckman Coulter) measurements were performed by central laboratories. Estimated glomerular filtration rate was calculated by the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation.

The clinical/proteomic panel was externally validated in a cohort of patients enrolled in the BACC (Biomarkers in Acute Cardiac Care) study (ClinicalTrials.Gov NCT02355457).¹² The BACC study is a prospective observational study that enrolled patients presenting with acute chest pain in the ED of the University Medical Center Hamburg‐Eppendorf in Germany beginning in July 19, 2013.¹² Informed consent was provided by the participants. For the purpose of this analysis, the first 303 patients who underwent a coronary angiogram for evaluation of their symptoms were included in this cohort. After excluding those with ST‐segment–elevation MI (n=46) and those with missing protein concentrations (n=16), we identified 241 patients for inclusion in our analysis (Figure S1). Enrollees in the BACC study had blood drawn immediately on presentation to the ED with their symptoms as described.¹² In the BACC study validation cohort, the ARCHITECT i1000SR (Abbott Diagnostics) hs‐cTnI was used. The limit of detection for the assay is 1.2 ng/L and the 99th percentile is 34 ng/L for men and 16 ng/L for women.

Within the recruiting sites, blood samples were obtained before angiography and application of heparin in a fasting state under standardized conditions and stored at −80°C until analysis.
Plasma levels of suPAR were determined with the suPARnostic standard enzyme‐linked immunosorbent assay (ViroGates, Birkerød, Denmark). The intra‐assay variation was 2.75%, and the interassay variation 9.17%. High‐sensitivity‐assayed troponin I (hs‐TnI) was measured using the Architect immunoassay (ARCHITECT i1000SR, Abbott Diagnostics, Chicago, IL). The intra‐assay variation was 6.68%, and the interassay variation 4.26%. CRP (C‐reactive protein) was determined by a highly sensitive, latex particle‐enhanced immunoassay (detection range, 0–20 mg/L; Roche Diagnostics, Mannheim, Germany). The measurement of NT‐proBNP (N‐terminal pro‐B‐type natriuretic peptide) was performed by electrochemiluminescence sandwich immunoassay (Roche Diagnostics, Mannheim, Germany). Serum creatinine was determined by standardized routine laboratory method. The Chronic Kidney Disease Epidemiology Collaboration equation was applied to calculate the eGFR.15 All biomarkers were measured in a blinded fashion.

At randomization and at 2 months, blood samples were collected in vacutainer tubes containing EDTA and were centrifuged immediately. Plasma was frozen in aliquots and stored at −70°C until analyzed centrally at the Uppsala Clinical Research Center. The cTnI concentration was determined with high‐sensitivity sandwich immunoassays on the ARCHITECT i1000SR (Abbott Diagnostics). The dynamic range is 0.7 to 50 000 ng/L, limit of detection in the Uppsala Clinical Research Center laboratory 1.3 ng/L, and the 99th percentile upper reference limit for healthy persons 23 ng/L.11 The coefficient of variation (CV) for this cTnI assay is 10% at 3.3 with a local CV of 7% at 21 ng/L. The cTnT concentration was determined with high‐sensitivity sandwich immunoassays on the Cobas Analytics e601 Immunoanalyzers (Roche Diagnostics). The measuring range is 3 to 10 000 ng/L, limit of detection 5 ng/L, and the 99th percentile upper reference limit for healthy persons 14 ng/L.12 The CV is 10% at 13 ng/L with a local CV of 3% at 27 ng/L. NT‐proBNP concentration was determined on the Cobas Analytics e601 Immunoanalyzers (Roche Diagnostics). The limit of detection is 5 ng/L. The analytical range is 20 to 35 000 ng/L. The upper reference limit is 269 in men and 391 ng/L in women.13 The CV is <10% at 30 ng/L with a local CV of 3% at 27 ng/L.14

Venous blood was drawn at randomization, before initiation of study treatment, using a 21/22‐gauge needle into vacutainer tubes containing EDTA. The blood was centrifuged within 30 minutes at 2000g for 10 minutes. The tubes were thereafter immediately frozen at −20°C or colder. Aliquots were stored at −70°C to allow for central batch analysis.
Plasma concentration of GDF‐15 was determined by Elecsys GDF‐15 precommercial assay kit P03 with the same standardization as the recently introduced routine reagent (Roche Diagnostics).9, 18 cTnI concentrations were measured on Architect i1000SR (Abbott Diagnostics) using hs assays. cTnT and NT‐proBNP were analyzed with high‐sensitivity assays on Cobas Analytics e601 and c501 Immunoanalyzer (Roche Diagnostics). These biochemical analyses were performed centrally at Uppsala Clinical Research Center laboratory (Uppsala, Sweden), according to the instructions of the manufacturer. Details about the characteristics of these assays have been reported previously.19, 20