Prehospital point-of-care testing for troponin: are the results reliable?

Swift assessment of patients presenting with chest pain results in faster treatment and improved outcomes. Allowing ambulance crews to use point-of-care (POC) devices to measure cardiac troponin I levels during transport of patients to the emergency department (ED) may result in earlier diagnosis of acute myocardial infarction, particularly in those patients without ST-segment elevation. The ability of POC devices to measure cardiac troponin I levels reliably in a moving ambulance has not previously been tested. Objective. This study was conducted to determine whether POC devices operated in a moving ambulance reliably duplicate the measurement of cardiac troponin I levels obtained by POC devices in the ED.

Blood samples were obtained in the ED and the hospital from patients reporting chest pain or other cardiac complaints. Troponin I assays were then performed in a moving ambulance using two POC devices. The POC devices were placed on flat surfaces in the rear of the ambulance. The ambulance driver was instructed to keep the ambulance moving in traffic while each assay was completed. A variety of routes were taken. Each set of two assays was completed entirely during a single simulated run. The results of the two assays performed in the moving ambulance were then compared with the results of the control assay, which was performed simultaneously in the ED on the same sample.

Forty-two whole-blood samples underwent troponin I assays in a moving ambulance. Thirteen (30.9%) assays were positive. One (2.4%) was excluded because of cartridge error. Two (4.8%) were excluded because of interfering substance. No significant difference in whole-blood troponin results was found between the assays performed in the moving ambulance and those performed in the ED (intraclass correlation coefficient 0.997; 95% confidence interval 0.994 to 0.998; p < 0.005).

When used in a moving ambulance, the POC device provided results of cardiac troponin I assays that were highly correlated to the results when the device was used in the ED. The feasibility, practicality, and clinical utility of prehospital use of POC devices must still be assessed. Key words: point-of-care systems; prehospital emergency care; troponin; reliability of results; ambulances; myocardial infarction; chest pain.