What is Sinai’s troponin assay? Answer: ARCHITECT STAT Troponin-I
A Global Task Force with involvement from the American Heart Association (AHA), American College of Cardiology Foundation (ACCF), European Society of Cardiology (ESC), and World Heart Federation (WHF) agreed on a universal definition of myocardial infarction that supports use of cTnI as a preferred biomarker for myocardial injury.
Elevated levels of cardiac TnI are detectable in serum within 4-6 hours after the onset of chest pain with peak in approximately 8-28 hours. It may remain elevated for 3- 10 days after an MI.
The ARCHITECT STAT Troponin-I assay analytical sensitivity is ≤ 0.01 ng/mL (≤ 0.01 μg/L) at the 95% level of confidence. The ARCHITECT STAT Troponin-I assay analytical specificity is ≤ 0.1% crossreactivity with skeletal troponin-I and ≤ 1% with cardiac troponin-C and cardiac troponin-T.
A study was performed that had compared 13 commonly troponin assays. Of note, the assay at Sinai is not a high sensitivity troponin-I (hsTnI) assay. While the limit of detection for the regular stat TnI is 0.01, that for the hsTnI is 0.001. Abbott iSTAT (different from the STAT Sinai has) and Ortho cTnI assays were two of the assays that more frequently had negative reads when all others were grossly positive aka be glad we don’t have these. Another study compared the ARCHITECT STAT TnI vs hsTnI. It showed the advantage of using the hsTnI to be in populations that appear with chest pain 1-3 hours after onset. Serial sampling using hsTnI can be reduced from 6-9 hours after the initial to 3 hours because it’s level of detection (LoD) was >50% of normals. Being able to more confidently do a repeat troponin 3 hours from the first as opposed to what would be 6 hours from with the regular STAT TnI would improve flow through an Emergency Department. Also, while the regular TnI assays take about 6 hours to diagnose an acute NSTEMI in terms of laboratory findings, the hsTnI assays cut that time more confidently to 3 hours and possibly as low as 1 hour in about 70% of patients with chest pain. The positive predictive value of the hsTnI goes from 75.1% to 95.8% after 3 hours. The first approved high sensitivity assay was approved in 2017 by the FDA despite being available in other parts of the world for years.
Shout-out to Sam Khan for requesting this topic as a TR pearl.