APIC243882241 - CME/CMLE - hs Troponin Techniques & Applications-APIC243882241

APIC243882241 - Educational Activity

Pdf Summary

This educational commentary by Ray North, MLS(ASCP)cm, discusses high-sensitivity cardiac troponin (hs-cTn) assays, their measurement units, clinical applications, and current guidelines, focusing on acute myocardial infarction (AMI) evaluation in emergency settings.<br /><br />Hs-cTn assays are vital for rapidly assessing patients suspected of acute coronary syndrome (ACS), enabling early rule-out or rule-in of AMI. Importantly, hs-cTn results are expressed in nanograms per liter (ng/L), representing a shift from standard troponin assays measured in nanograms per milliliter, allowing more precise quantification.<br /><br />Two key analytical thresholds are noted: the limit of detection (LoD), the lowest detectable concentration, and the limit of quantitation (LoQ), the lowest concentration measurable with acceptable imprecision (20% coefficient of variation). Although guidelines like the 2021 AHA/ACC recommend using LoD for early AMI rule-out, in the US only LoQ values are FDA-cleared for reporting, making LoD-based strategies impractical clinically. The distinction between LoD and LoQ, though subtle, is important for accurate interpretation and patient safety.<br /><br />Additionally, hs-cTn 99th percentile upper reference limits differ overall and by sex, with women having lower thresholds that may permit earlier detection of cardiac injury. Recognizing sex-specific cutoffs improves diagnostic accuracy.<br /><br />Limitations include potential false positives from heterophile antibodies, chronic muscle diseases, or assay interferences, and rare false negatives due to anti-troponin antibodies or hemolysis. Timing of sample collection is crucial, as very early or late presentations may yield misleading results.<br /><br />In conclusion, clinicians should understand the technical aspects of hs-cTn testing, including units, thresholds, sex-specific values, and assay limitations, and integrate these with clinical and imaging findings for precise diagnosis and management of acute chest pain.

Keywords

high-sensitivity cardiac troponin

hs-cTn assays

acute myocardial infarction

AMI evaluation

limit of detection

limit of quantitation

99th percentile upper reference limit

sex-specific cutoffs

acute coronary syndrome

troponin assay limitations