Quality Specifications of Troponin Measurement Methods
المؤلف:
Marcello Ciaccio
المصدر:
Clinical and Laboratory Medicine Textbook 2021
الجزء والصفحة:
p297-298
2025-08-31
269
All the most recent national and international guidelines published since 2000 recommend an increase in cTnI and cTnT concentrations above the 99th percentile of the distribution of values measured in a reference population of healthy individuals as a decision level for the diagnosis of AMI . The same guidelines recommend, at this concentration, an analytical imprecision ≤10% (expressed as coefficient of variation [CV]). However, only since 2007 methods with these quality specifications have been introduced commercially in Italy. Therefore, in accordance with national and international guidelines, only immunometric methods measuring the 99th percentile of the distribution of cTnI and cTnT concentrations in the reference population with a CV% ≤10% should be defined as new generation high sensitivity methods for troponin measurement. These high analytical sensitivity methods should also be able to measure cTnI and cTnT in the majority (>75% of subjects) of healthy adults. Newer generation methods, which have intermediate imprecision (CV between 10 and 20%) at the 99th percentile level, should be defined as clinically usable, i.e., they can be used in clinical practice but should not be defined as having higher sensitivity. Finally, methods (such as most POCT systems) that have an inaccuracy >20% should not be used to diagnose AMI but only for the initial screening of patients with suspected acute coronary syndrome, especially when higher sensitivity methods are not available.
Another advantage of introducing methods with higher analytical sensitivity is the possibility of measuring the bio marker in healthy subjects, including pediatric age. The most recent studies have shown that circulating cTnI and cTnT levels in healthy subjects depend on age and sex. From a clinical point of view, it is essential to emphasize that the 99th per centile varies greatly when calculated in a population of apparently healthy subjects over 65 compared to the value measured in blood donors between 20 and 55 years.
The immunometric methods for measuring cTnI currently available have very different reference values and provide different results since they use different antibodies and calibration materials. The method for the measurement of cTnT, which is governed by an international patent and uses control materials and reagents from one manufacturer, allows for more harmonized results, even though the reagents are applied to different platforms. Because cardiac troponins' decision values (99th percentile of the reference population) are both method- and population-dependent, national guidelines recommend that clinicians and laboratory medicine experts jointly agree on the most appropriate decision levels according to the clinical context in which the test is applied.
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