The use of a point of care high sensitivity troponin in the investigation of patients presenting to the Emergency Department with undifferentiated chest pain
Authors: Aldous S , Pickering J , Hamill L , Joyce L , Than M 
Published: October 2024

Abstract

Background
In 2012 in a hospital, New Zealand, a chest pain pathway was instituted for the use in patients presenting to the Emergency Department (ED) with undifferentiated chest pain. This reduced hospital admissions and ED length of stay (LOS) without adversely affecting outcomes. The pathway consists of risk stratification combined with ECG and troponin testing. The pathway suggests, but does not enforce, that low risk patients can be discharged after a single troponin, intermediate risk patients are for serial troponins (which can be done in ED or the next day in the community), with further testing if appropriate, and high risk patients are reviewed by Cardiology or General medicine. In August 2023, Siemens point of care high sensitivity troponin I (POC-hsTnI) was introduced for the use in ED, although Beckman laboratory troponin I (Lab–hsTnI) is still available. A POC test reduces result turnaround times but until recently there has been a lack of POC assays fulfilling criteria for "high sensitivity".

Purpose
To ascertain whether the availability of a POC-hsTnI in the ED is a viable option for use in the chest pain pathway

Methods
A 1 month "snap shot" of all consecutive patients presenting to the ED with chest pain was undertaken and the patients followed for adverse events using electronic notes review. October 2023 was selected for the post POC-hsTnI period and compared with April 2022.

Results
There were 688 patients presenting to ED with undifferentiated chest pain during October 2023 with a type 1 acute myocardial infarction (AMI) rate of 80 (11.6%), median age 58 (41-72), female 335 (48.7%). POC-hsTnI was used in isolation in 377 (54.8%), in conjunction with Lab-hsTnI in 218 (31.7%) and Lab-hsTnI was used alone in 93 (13.5%). The median turnaround time for POC-hsTnI was 11 minutes (10-11) compared with Lab-hsTnI 87 minutes (61-129). The POC-hsTnI was less sensitive for AMI than the Lab-hsTnI on presentation using the upper reference limit, 72.1% (60.6-81.6) versus 91.5% (83.0-96.4). However, when used with risk stratification, there were no excess adverse events (cardiac death or AMI) at 4 months in patients discharged with a diagnosis of non-cardiac chest pain – 7 (1.4%) (n=495) versus 5 (1.2%), (n=424) in 2022. Median LOS in the ED was 4.4 hours (2.9-6.2) versus 4.0h (3.0-5.9) in 2022. However, a higher proportion of patients had a second cTn: 414 (60.2%) versus 309 (48.4%) and a lower proportion had their second troponin the next day in the community, 28 (6.7%) versus 56 (18.1%).

Conclusion
The use of a POC-hsTnI is a practical solution to reduce turnaround times for troponin results and has the potential to reduce LOS or allow serial troponins to be measured in a timely manner during their ED visit, obviating the need for a next day community troponin. Whilst POC-hsTnI has a lower early sensitivity for AMI, the use of POC-hsTnI as part of a pathway does not adversely affect outcomes.