Chest pain…everyone gets it…sometimes when a patient says they have chest pain I get chest pain. What’s the solution to this chest pain epidemic? Troponins! Well not so fast because they aren’t fast…especially when the lab tells you, “no troponins here…”
In particular High Sensitivity Troponin T (hs-cTnT) is the new kid on the block that may help speed up our chest pain diagnostic algorithm.
Reichlin et al 2015 in the APACE study evaluated the use of Troponin T in 1320 patients to rule out/rule in MI compared against the “gold standard” 2 independent cardiologists incorporating all of the data (ECGs,Cath reports…); [renal failure patients requiring dialysis and STEMI patients excluded]. They looked at troponins at time zero and 1hr later in 3 groups: (1) Rule-In MI, (2) Rule-Out MI, (3) Observational Grp.
What They Found:
(1) Rule-In MI [hs-cTnT >52 ng/L or Δ of >5 ng/L within 1st hr] 16% patients–>Rule-in group Specificity 95.7%/PPV 78.2%
(2) Rule-Out MI [hs-cTnT<12ng/L and Δ within 1st hr of < 3 ng/L] 60% of patients–>Rule-out group Sensitivity 99.6%/NPV 99.9% ; 1 patient had an MI-elderly lady whose hs-cTnT rose after the 1hr timeframe
(3) Observation grp (fit neither criteria) 24% patients–>18.6% within this group had MIs (59 patients hmmm…)
Limitations: (1) Low PPV–>a lot of false positives (but they had fairly significant pathology such as Takotsubo’s) (2) Observational grp–> what do we do with these patients? (3) change in TnT may be a property of the assay and not the patient therefore changes may not be clinically relevant (4) A 3rd cardiologist was needed for confirmation of MI diagnosis in approx 12% of patients
Mueller et al 2016 looked at use of TnT for 1hr Diagnosis of Chest Pain in the TRAPID-AMI Study: They evaluated 1282 patients who presented to the ER with suspicion for MI [STEMI patients not excluded] and use of 0hr/1hr hs-cTnT for diagnosis of MI. Their “gold standard” was evaluation by 2 independent cardiologist who looked at all the data. Their hs-cTnT cutoffs for the Rule-In/Rule-Out/Obs groups were the similar to the Reichlin et al 2015 study.
What They Found:
(1) Rule-In MI 14% patients; Specificity 96.1%/PPV 77.2%
(2) Rule-Out MI 63% patients; Sensitivity 96.7%/NPV 99.1% ; 7 patients had an MI *Troponin I was elevated in 5/7 patients at time 0 or within 1hr; revascularization in 1/7 patients
(3) Obs Grp 22% patients; 22.5% within this group had MIs (62 patients w/ MI)
- 0hr/1hr TnT is sensitive but has some limited specificity (a good number of false positives although these false positive do have relevant pathology such as Takotsubo’s)
- The rare times TnT at 0hr/1hr misses MI perhaps Troponin I should come to the rescue!
- Sinai uses Troponin I but a lot of places use TnT
- Further stratify management for groups: like low risk chest pain group can maybe get 1 TnT instead of serial testing
- What to do with the Observation Group?! (Not sure what they did)
SGEM#160: Oh Baby, You’re Too Sensitive – High Sensitivity Troponin. http://thesgem.com/2016/09/sgem160-oh-baby-youre-too-sensitive-high-sensitivity-troponin/
SGEM#128: One Hour AMI Rule Out/Rule In (Harder, Better, Faster?) http://thesgem.com/2015/09/sgem128-one-hour-ami-rule-out-harder-better-faster/
- Reichlin, T., Twerenbold, R., Wildi, K., Gimenez, M. R., Bergsma, N., Haaf, P., … & Stelzig, C. (2015). Prospective validation of a 1-hour algorithm to rule-out and rule-in acute myocardial infarction using a high-sensitivity cardiac troponin T assay. Canadian Medical Association Journal, 187(8), E243-E252.
- Mueller, C., Giannitsis, E., Christ, M., Ordóñez-Llanos, J., McCord, J., Body, R., … & French, J. (2016). Multicenter evaluation of a 0-hour/1-hour algorithm in the diagnosis of myocardial infarction with high-sensitivity cardiac troponin T. Annals of emergency medicine.
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