RESUMO
BACKGROUND: Siemens Healthcare Diagnostics has four commercially available assays on different analytical platforms using different methodologies to generate signal. We assessed the analytical performance of the Dimension EXL hs-cTnI assay (LOCI method) across different matrices and compared it to two different acridinium ester-based hs-cTnI assays (ADVIA Centaur and Abbott ARCHITECT). METHODS: The analytical sensitivity and precision below the 99th-percentile was determined for the Dimension EXL hs-cTnI assay. Method comparisons were performed between the Dimension EXL contemporary cTnI and the hs-cTnI assays, between different matrices for the EXL hs-cTnI assay (serum, lithium heparin and EDTA plasma), and between different hs-cTnI assays (EXL versus ADVIA Centaur or Abbott ARCHITECT) using non-parametric analyses. RESULTS: The limit of blank and detection were 0.9â¯ng/L and 1.7â¯ng/L, respectively, with imprecision of 5.8% at 8.6â¯ng/L and 3.2% at 47.5â¯ng/L. Comparison between the EXL contemporary cTnI and hs-cTnI assay (range: 2.6-4214â¯ng/L) yielded proportional lower concentrations for the hs-cTnI assay (slopeâ¯=â¯0.86; 95%CI: 0.81 to 0.96, nâ¯=â¯40); however, there was no difference in concentrations below 100â¯ng/L between the assays (median differenceâ¯=â¯-2.7â¯ng/L; 95%CI: -9.8 to 9.3). Passing-Bablok regression analysis with EDTA plasma yielded proportionally higher concentrations with the EXL hs-cTnI versus Abbott hs-cTnI (slopeâ¯=â¯1.45; 95%CI: 1.02-1.86, nâ¯=â¯40) with proportionally lower concentrations with EDTA versus lithium heparin plasma with the EXL hs-cTnI assay alone (slopeâ¯=â¯0.93; 95%CI: 0.90 to 0.99, nâ¯=â¯40). Comparison with Abbott hs-cTnI concentrations below 100â¯ng/L in the three matrices, indicated that the EXL hs-cTnI assay yielded higher concentrations (median difference range: 3.4-9.4â¯ng/L), with differences also evident when comparing the EXL hs-cTnI assay to the ADVIA Centaur hs-cTnI assay. CONCLUSION: The Siemens EXL hs-cTnI assay meets the analytical criteria for a high-sensitivity assay, with assay specific cutoffs important to maximize clinical performance.