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Ann Clin Biochem. 2014 Jul;51(Pt 4):476-84. doi: 10.1177/0004563213499737. Epub 2013 Sep 20.

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

Author information

1
PathWest, Royal Perth Hospital, Perth, Australia nicola.sawyer@health.wa.gov.au.
2
PathWest, Royal Perth Hospital, Perth, Australia.

Abstract

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.

KEYWORDS:

Troponin; analytes

PMID:
24056812
DOI:
10.1177/0004563213499737
[Indexed for MEDLINE]
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