Impact of the Australian gender specific thresholds using the Abbott high sensitivity troponin I assay in clinical care.

The aim of this study was to ascertain the impact of gender specific hs-TnI thresholds in a clinical setting and determine the clinical characteristics and discharge diagnosis for individuals presenting to the Emergency Department (ED) with elevated troponin I with the Abbott high-sensitivity troponin I (hs-TnI) assay, but non-elevated troponin I on the previous generation assay (STAT TnI-II). Medical records of individuals presenting to the Royal Perth Hospital ED with elevated hs-TnI between 12 November 2013 and 24 December 2013 were retrospectively reviewed. The 99th percentile hs-TnI thresholds were ≥26 ng/L for males and ≥16 ng/L for females. TnI-II assays were performed concomitantly. In total, 1449 individuals [855 (59%) males] had 3580 troponin measurements. hs-TnI was elevated in 1569 (43.8%) measurements. Elevated hs-TnI with normal TnI-II was found in 120 (8.3%) individuals: 77 (64%) females and 43 (36%) males. Eight (6.7%) individuals were diagnosed with acute coronary syndrome (ACS): four (9.3%) males and four (5.2%) females. Other cardiac aetiologies were found in 33 (42%) females and 17 (40%) males. Individuals with elevated hs-TnI had high rates of hypertension (80%), diabetes mellitus (33%), cardiac failure (23%), aspirin use (53%) and lipid lowering therapy (52%). Significantly fewer females than males with discrepant troponin I results had previous ischaemic heart disease. The hsTnI assay identifies 8% more individuals with elevated troponin in an acute setting, with a female predominance (64%). However, only 6.7% of these individuals with multiple cardiovascular risk factors were diagnosed with ACS, a ∼0.5% increase overall. Outcome studies are required to determine if the Australian hs-TnI thresholds are clinically appropriate.

Outliers affecting cardiac troponin I measurement: comparison of a new high sensitivity assay with a contemporary assay on the Abbott ARCHITECT analyser.

BACKGROUND: False-positive cardiac troponin (Tn) results caused by outliers have been reported on various analytical platforms. We have compared the precision profile and outlier rate of the Abbott Diagnostics contemporary troponin I (TnI) assay with their high sensitivity (hs) TnI assay. METHODS: Three studies were conducted over a 10-month period using routine patients' samples. TnI was measured in duplicate using the contemporary TnI assay in Study 1 and Study 2 (n = 7011 and 7089) and the hs-TnI assay in Study 3 (n = 1522). Critical outliers were defined as duplicate results whose absolute difference exceeded a critical difference (CD = z x √2 x SDAnalytical) at a probability level of 0.0005, with one of the results on the opposite side of the decision limit to its partner. RESULTS: The TnI concentration at 10% imprecision (coefficient of variation) for the contemporary TnI assay was 0.034 µg/L (Study 1) and 0.042 µg/L (Study 2), and 0.006 µg/L (6 ng/L) for the hs-TnI assay. The critical outlier rates for the contemporary TnI assay were 0.51% (Study 1) and 0.37% (Study 2) using a cut-off of 0.04 µg/L, and 0% for the hs-TnI assay using gender-specific cut-offs. CONCLUSION: The significant number of critical outliers detected using the contemporary TnI assay may pose a risk for misclassification of patients. By contrast, no critical outliers were detected using the hs-TnI assay. However, the total outlier rates for both assays were significantly higher than the expected variability of either assay. The cause of these outliers remains unclear.