Difference between revisions of "High-sensitivity Troponin-T"

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The U.S. FDA approved the first high-sensitivity troponin assay, the Roche Diagnostics ''Elecsys Troponin T (TnT) Gen 5 Stat'' test, in March 2017.
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As of November 12, 2019, the cardiac troponin assay utilized by the Yukon-Kuskokwim Delta Regional Hospital (YKDHR) is the Roche Diagnostics [https://diagnostics.roche.com/us/en/products/params/elecsys-troponin-t-high-sensitive-tnt-hs.html ''Elecsys® Troponin T Gen 5 STAT''].  This is a high-sensitivity fifth-generation cardiac troponin assay.
  
Yukon-Kuskokwim Delta Regional Hospital (YKDHR) adopted this high-sensitivity cardiac troponin-T (Hs-cTnT) assay on November 12, 2019.
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Cardiac troponin assays measure the concentration of either troponin-T or troponin-I.  Both high-sensitivity and contemporary troponin assays measure the exact same molecule, but high-sensitivity assays measure ''much'' more precisely and at ''much'' lower concentrations. The high-sensitivity and contemporary assays can be distinguished by the units in which they are reported:  high-sensitivity assays are reported in ng/'''L''' whereas the contemporary assays are reported in ng/'''mL'''.
 
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:::Conversion between the results can be done by moving the decimal point three places:  a contemporary concentration of 0.4 ng/mL is equivalent to a high-sensitivity concentration of 400 mg/mL, and a high-sensitivity concentration of 14 ng/L is equivalent to a contemporary concentration of 0.014 ng/L.  This latter conversion illustrates that the high-sensitivity assays accurately measure concentrations which are ''two orders of magnitude'' lower than the assay we were previously using.
The high-sensitivity and contemporary troponin-T assays can be distinguished by the units in which they are reported:  Hs-cTnT is reported in ng/'''L''' whereas the contemporary assay (cTnT) is reported in ng/'''mL'''.
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Though high-sensitivity troponin assays have been used in Europe and Canada since approximately 2009, the first U.S. FDA approval occurred in 2017. 
  
 
''NOTE:  The information below is not a guideline, but rather excerpts and links intended to augment and/or help develop clinical judgement.''
 
''NOTE:  The information below is not a guideline, but rather excerpts and links intended to augment and/or help develop clinical judgement.''
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__TOC__
 
__TOC__
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== Definition ==
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To qualify as ''high-sensitivity'' (or ''highly-sensitive''), a cardiac troponin assay must be able to detect a level of cardiac troponin in >50% of normal individuals.<ref>High-Sensitivity Cardiac Troponin in the Evaluation of Possible AMI. American College of Cardiology. https://www.acc.org/latest-in-cardiology/articles/2018/07/16/09/17/high-sensitivity-cardiac-troponin-in-the-evaluation-of-possible-ami. Accessed December 3, 2019.</ref>  This means that the majority of patients ''without'' cardiac ischemia ''will have'' a detectable level of cardiac troponin.  This has substantial implications for how clinician conceptualize and interpret cardiac troponin levels.
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== Level versus Delta (Δ) ==
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With contemporary troponin assays, a troponin level was not detectable in most patients who lack cardiac ischemia. Therefore the ''level'' of the troponin was the focus while the subsequent ''delta (Δ)'' (i.e. a change) was a secondary consideration.
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Due to the high-sensitivity assays' ability to detect a troponin level in most patients who lack cardiac ischemia, many experts recommend a reversal in diagnostic thinking:  for most patients the delta (Δ) should be the focus while the level is a secondary consideration.<ref>Helman, A. McRae, A. Lang, E. Low Risk Chest Pain and High Sensitivity Troponin – A Paradigm Shift. Emergency Medicine Cases. July, 2019. https://emergencymedicinecases.com/low-risk-chest-pain-high-sensitivity-troponin. Accessed December 2, 2019.</ref>
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However, there are initial levels below and above which a delta is not required:
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::::* If >= 3 hours since onset of symptoms and a normal EKG, then an initial troponin level < 6 ng/L can rule-out ACS.
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::::* In the context of new symptoms consistent with ACS, an initial troponin level >100 ng/L rules-in ACS.
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<br>
 +
<br>
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== Relative versus Absolute Delta (Δ) ==
 +
With contemporary troponin assays, a delta of 20% was often used to rule-in ACS.
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 +
However, common situations arise with high-sensitivity troponin assays where relative deltas can lead to both over- and underdiagnosis.  For example, if the initial troponin level is 5 ng/L, then a delta of 1 ng/L is a 20% rise, despite the change being within the expected margin of error of the assay.  Alternately, the 20% relative change can miss ACS in patients with chronically elevated troponin levels.
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Therefore many experts recommend using an absolute delta to rule-out or rule-in ACS.
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<br>
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<br>
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== Δh Terminology ==
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::::* 0h: Troponin drawn at ED arrival
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::::* Δ1h: Troponin drawn 1 hour after ED arrival
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::::* Δ2h: Troponin drawn 2 hours after ED arrival
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::::* Δ3h: Troponin drawn 3 hours after ED arrival
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A 0h-1h delta (i.e. a change over one hour, either increase or decrease) >= '''3''' ng/L is considered positive for acute myocardial injury (AMI).<br>
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A Δ1h (i.e. the change in Hs-cTnT from ED arrival to 1 hour later) >= '''3''' ng/L is considered positive for acute myocardial injury (AMI).<br>
 
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Per the ACC white paper (see below):<br>
 
Per the ACC white paper (see below):<br>
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== Diagnostic Algorithm ==
 
== Diagnostic Algorithm ==
Currently there are no experimentally validated diagnostic algorithms using Hs-cTnT.  However, the internet contains several somewhat similar algorithms on reputable medical sites.  In particular, the ACEP Webinar (see below, page 16) displays the following diagnostic algorithm:
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The internet contains several somewhat similar algorithms on reputable medical sites.  In particular, the ACEP Webinar (see below, page 16) displays the following diagnostic algorithm:
 
<br><br>
 
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[[File:UTSW-Parkland hs-cTnT pathway.PNG|1000px]]
 
[[File:UTSW-Parkland hs-cTnT pathway.PNG|1000px]]
 
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Note that this algorithm does not include risk stratification, such as with the HEART score.  Other algorithms separate out Hs-cTnT and call the risk stratification a HEAR score (or modified-HEART score) and guide diagnosis/management based upon different combinations of Hs-cTnT and HEAR values.
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Note that this algorithm does not include risk stratification, such as with the HEART score.  Yet the same Webinar contains other algorithms which separate out Hs-cTnT and call the risk stratification a HEAR score (or "modified-HEART" score) and guide diagnosis/management based upon different combinations of Hs-cTnT and HEAR values.  Yet other algorithms in the same Webinar recommend skipping risk stratification in those who have low- or high-risk EKG/Hs-cTnT results and only risk stratifying those with intermediate-risk EKG/Hs-cTnT results.
 
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'''ACEP'''
 
'''ACEP'''
 
:[https://www.acep.org/globalassets/sites/acep/media/equal-documents/webinar_chestpainw3_hsctn2.pdf ''Webinar: Incorporating High-Sensitivity Troponin into Your ED'']
 
:[https://www.acep.org/globalassets/sites/acep/media/equal-documents/webinar_chestpainw3_hsctn2.pdf ''Webinar: Incorporating High-Sensitivity Troponin into Your ED'']
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:[https://www.acep.org/patient-care/clinical-policies/nonst-elevation-acute-coronary-syndromes/ ''Critical Issues in the Evaluation and Management of Emergency Department Patients with Suspected Non–ST-Elevation Acute Coronary Syndromes'' (Jun 2018)]
 
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'''MD Calc'''
 
'''MD Calc'''
 
:[https://www.mdcalc.com/heart-score-major-cardiac-events HEART Score for Major Cardiac Events]
 
:[https://www.mdcalc.com/heart-score-major-cardiac-events HEART Score for Major Cardiac Events]
 
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== References ==

Revision as of 08:56, 3 December 2019

As of November 12, 2019, the cardiac troponin assay utilized by the Yukon-Kuskokwim Delta Regional Hospital (YKDHR) is the Roche Diagnostics Elecsys® Troponin T Gen 5 STAT. This is a high-sensitivity fifth-generation cardiac troponin assay.

Cardiac troponin assays measure the concentration of either troponin-T or troponin-I. Both high-sensitivity and contemporary troponin assays measure the exact same molecule, but high-sensitivity assays measure much more precisely and at much lower concentrations. The high-sensitivity and contemporary assays can be distinguished by the units in which they are reported: high-sensitivity assays are reported in ng/L whereas the contemporary assays are reported in ng/mL.

Conversion between the results can be done by moving the decimal point three places: a contemporary concentration of 0.4 ng/mL is equivalent to a high-sensitivity concentration of 400 mg/mL, and a high-sensitivity concentration of 14 ng/L is equivalent to a contemporary concentration of 0.014 ng/L. This latter conversion illustrates that the high-sensitivity assays accurately measure concentrations which are two orders of magnitude lower than the assay we were previously using.

Though high-sensitivity troponin assays have been used in Europe and Canada since approximately 2009, the first U.S. FDA approval occurred in 2017.

NOTE: The information below is not a guideline, but rather excerpts and links intended to augment and/or help develop clinical judgement.




Definition

To qualify as high-sensitivity (or highly-sensitive), a cardiac troponin assay must be able to detect a level of cardiac troponin in >50% of normal individuals.[1] This means that the majority of patients without cardiac ischemia will have a detectable level of cardiac troponin. This has substantial implications for how clinician conceptualize and interpret cardiac troponin levels.

Level versus Delta (Δ)

With contemporary troponin assays, a troponin level was not detectable in most patients who lack cardiac ischemia. Therefore the level of the troponin was the focus while the subsequent delta (Δ) (i.e. a change) was a secondary consideration.

Due to the high-sensitivity assays' ability to detect a troponin level in most patients who lack cardiac ischemia, many experts recommend a reversal in diagnostic thinking: for most patients the delta (Δ) should be the focus while the level is a secondary consideration.[2]

However, there are initial levels below and above which a delta is not required:

  • If >= 3 hours since onset of symptoms and a normal EKG, then an initial troponin level < 6 ng/L can rule-out ACS.
  • In the context of new symptoms consistent with ACS, an initial troponin level >100 ng/L rules-in ACS.



Relative versus Absolute Delta (Δ)

With contemporary troponin assays, a delta of 20% was often used to rule-in ACS.

However, common situations arise with high-sensitivity troponin assays where relative deltas can lead to both over- and underdiagnosis. For example, if the initial troponin level is 5 ng/L, then a delta of 1 ng/L is a 20% rise, despite the change being within the expected margin of error of the assay. Alternately, the 20% relative change can miss ACS in patients with chronically elevated troponin levels.

Therefore many experts recommend using an absolute delta to rule-out or rule-in ACS.

Δh Terminology

  • 0h: Troponin drawn at ED arrival
  • Δ1h: Troponin drawn 1 hour after ED arrival
  • Δ2h: Troponin drawn 2 hours after ED arrival
  • Δ3h: Troponin drawn 3 hours after ED arrival



Cutoffs

Hs-cTnT is considered "positive" when above the gender-specific 99th percentile URL (upper reference range). Per eMail from Scott Cox (YKDHR Director of Diagnostic Services) on 11/10/2019, the following cutoff are recommended for our assay:

Positive Values
Women >= 14 ng/L
Men >= 22 ng/L


A Δ1h (i.e. the change in Hs-cTnT from ED arrival to 1 hour later) >= 3 ng/L is considered positive for acute myocardial injury (AMI).

Per the ACC white paper (see below):

  • A single Hs-cTnT >= 100 ng/L is diagnostic of AMI (in the appropriate clinical context).
  • When chest pain has been present for >= 2 hours, a single Hs-cTnT < 6 ng/L has been reported to rule out AMI with essentially 100% negative predictive value.


Diagnostic Algorithm

The internet contains several somewhat similar algorithms on reputable medical sites. In particular, the ACEP Webinar (see below, page 16) displays the following diagnostic algorithm:

UTSW-Parkland hs-cTnT pathway.PNG

Note that this algorithm does not include risk stratification, such as with the HEART score. Yet the same Webinar contains other algorithms which separate out Hs-cTnT and call the risk stratification a HEAR score (or "modified-HEART" score) and guide diagnosis/management based upon different combinations of Hs-cTnT and HEAR values. Yet other algorithms in the same Webinar recommend skipping risk stratification in those who have low- or high-risk EKG/Hs-cTnT results and only risk stratifying those with intermediate-risk EKG/Hs-cTnT results.

Helpful Links

ACC (American College of Cardiology)

High-Sensitivity Cardiac Troponin in the Evaluation of Possible AMI (July 16, 2018)
SUMMARY: Fourth Universal Definition of Myocardial Infarction (Aug 25, 2018)


ACEP

Webinar: Incorporating High-Sensitivity Troponin into Your ED
Critical Issues in the Evaluation and Management of Emergency Department Patients with Suspected Non–ST-Elevation Acute Coronary Syndromes (Jun 2018)


MD Calc

HEART Score for Major Cardiac Events


References

  1. High-Sensitivity Cardiac Troponin in the Evaluation of Possible AMI. American College of Cardiology. https://www.acc.org/latest-in-cardiology/articles/2018/07/16/09/17/high-sensitivity-cardiac-troponin-in-the-evaluation-of-possible-ami. Accessed December 3, 2019.
  2. Helman, A. McRae, A. Lang, E. Low Risk Chest Pain and High Sensitivity Troponin – A Paradigm Shift. Emergency Medicine Cases. July, 2019. https://emergencymedicinecases.com/low-risk-chest-pain-high-sensitivity-troponin. Accessed December 2, 2019.