Comparison of new point-of-care troponin assay with high sensitivity troponin in diagnosing myocardial infarction

- Point of care (POC) troponin assays have previously had inferior analytical sensitivity compared with laboratory assays.
- This study compares a new generation POC assay with an older generation POC assay and a high sensitivity assay.
- The sensitivity of the new generation POC assay for the diagnosis of myocardial infarction or for the prediction of MACE when used in an accelerated diagnostic protocol (0h/2h post presentation troponin, ECG and TIMI score), is superior to an old generation POC assay, and comparable to a high sensitivity troponin. Specificity is reduced.
- Improved sensitivity of POC assays makes uptake into clinical practice more acceptable and use of such tests may speed up discharge times, improve hospital overcrowding and be useful in remote practices with poor access to laboratory assays.

ObjectivesThe aim of this study is to compare a new improved point of care cardiac troponin assay (new POC-cTnI) with 1. its predecessor (old POC-cTnI) and 2. a high sensitivity assay (hs-cTnI) for the diagnosis of acute myocardial infarction (AMI) and for major adverse cardiac events (MACE) by 30 days.MethodsThis is a single centre observational study, set in Christchurch Hospital, New Zealand. Patients presenting to the emergency department with non-traumatic chest pain underwent blood sampling at 0 h and 2 h post presentation for analysis with the 3 cTnI assays for the outcome of AMI and for analysis using an accelerated diagnostic protocol (ADP-normal 2 h troponins, normal electrocardiograms and Thrombolysis In Myocardial Infarction (TIMI) score of 0 or ≤ 1) for 30 day MACE.ResultsOf 962 patients, 220 (22.9%) had AMI. Old POC-cTnI was least sensitive at 70.0% (65.4-73.9%) by 2 h (p < 0.001). New POC-cTnI, sensitivity 93.6% (89.9-96.2%) had similar sensitivity to hs-cTnI, sensitivity 95.0% (91.5-97.3%) (p = 0.508). There were 231 (24.0%) patients with 30 day MACE. When used as part of the ADP, all assays had 100% (98.0-100%) sensitivity using TIMI = 0. Sensitivities of new POC-cTnI ADP, 98.3% (95.4-99.4%), old POC-cTnI, 96.5% (93.2-98.4%) and hs-cTnI, 98.7% (96.0-99.7%) were similar (p = 0.063-0.375) using TIMI ≤ 1.ConclusionsA new POC-cTnI has improved sensitivity for AMI and MACE compared with its predecessor and comparable sensitivity to a high sensitivity assay. Now that sensitivities of the POC assay are improved, the new assay may be a useful alternative to central laboratory assays when rapid turn-around times are not possible.