A new more sensitive Troponin I test is available

By Dr David Deam
Published April 2019

Australian Clinical Labs is pleased to advise that a new more sensitive Troponin I assay is replacing our existing laboratory based troponin assay.

The assay uses two new monoclonal antibodies and reagents to deliver a 10 fold increase in test functional sensitivity.

What Will Change?

Troponin units will change from ug/L to ng/L due to the improved sensitivity.
Reference Ranges: New reference ranges will reflect the performance of the new assays. We will also introducing gender specific ranges which are more significant due to the improved sensitivity of the assay.
The reference ranges differ slightly depending on the type of instrument used (see table below).
There will be a higher number of results where the Troponin I level is measurable.

Instrument	Males	Females
	Serum 99% ng/L	Serum 99% ng/L
Siemens Centaur	58	40
Siemens Atellica	54	39
Siemens Dimension	72	48

What Will Remain The Same?

Turnaround times for troponin results
Quantitative comparisons cannot be made between Troponin I and T, or between point of care (POC) devices and laboratory-based immunoassays.
Troponin elevation is not specific for acute myocardial infarction.

Advantages of a High-Sensitivity Troponin I Assay

Increasing sensitivity of troponin assays enables detection of smaller areas of necrosis
Optimise negative predictive value: high-sensitivity troponin allows for a more rapid triage of patients suspected of AMI based on improved discrimination of low-level troponin I concentrations at presentation as well as over time.
For early presenters: low-end precision allows early detection of significant change in troponin I concentrations, which may not have yet exceeded the 99th percentile limit.
A Serial sampling strategy is still recommended (preferably using the same instrument). Time between tests may be shortened with hsTNI assays based on published guidelines. Chest pain protocols can be reviewed and modified if necessary to reflect the new assay.

What classifies a Troponin assay as having high sensitivity

This requires a test coefficient of variation of < 10% at a 99th percentile level of a normal population, and
Measureable concentrations below the 99th percentile should be attainable with a concentration above the assay’s limit of detection for at least 50% of healthy individuals

Note that the the high-sensitivity refers to the assay’s performance characteristics, not a difference in form of cardiac troponin being tested.

For further information, please contact your local Australian Clinical Labs Pathologists.

About the Author

Dr David Deam

MBBS MAACB FRCPA

Location: Clayton (VIC)

Speciality: Chemical Pathology

Areas of Interest:

endocrine function testing
laboratory automation
protein abnormalities

About

Dr Deam graduated with Honours in Medicine from Monash University in 1978 and obtained his FRCPA in 1985 following postgraduate training in Biochemistry at the Royal Melbourne Hospital. After several posts in Chemical Pathology at the Royal Melbourne Hospital and the Royal Women’s Hospital, he was appointed Head of Chemical Pathology at the Royal Melbourne in 1996. He joined Gribbles Pathology (now Australian Clinical Labs) in 1998.

Dr Deam has played an active role in teaching scientific, nursing and medical staff at both undergraduate and postgraduate levels and has been an examiner for the Australasian Association of Clinical Biochemists as well as the Royal College of Pathologists of Australasia.

Dr Deam’s research interests and publications include work on thyroid function testing, various aspects of diagnostic protein measurement and the rational use of biochemical tests. His special interests include testing of endocrine function; protein abnormalities; as well as laboratory automation and application of computing to pathology services.

Troponin I