A rapid clotting serum tube containing a thrombin-based clot activator, the BD Vacutainer ® Rapid Serum Tube (RST TM ; BD, Franklin Lakes, NJ, USA), gives a faster clotting time of around 5 min, compared to 30 min for standard serum tubes (BD). The faster clotting time offers potential improvement to turnaround times for serum samples. RST tubes have therefore, previously been evaluated using various cardiac troponin (cTn) assays (including contemporary cTnI assays [1, 2] and cTnT assays [3][4][5], showing generally good agreement with serum [4, 5] and plasma specimens [1][2][3]. We wanted to compare cTnI results in RST and plasma (a common specimen for stat testing) using a new high-sensitivity cTnI assay.We collected three blood tubes, including an RST, BD Vacutainer PST TM II (PST; heparin plasma, gel separator) and a BD Vacutainer Heparin Tube (non-gel, heparin plasma), from patients presenting to an emergency department (ED) and requiring a blood test, over an 8-day period. cTnI was promptly assayed on all three tubes using the STAT High Sensitive Troponin-I assay (Abbott Diagnostics, Abbott Park, IL, USA) with laboratory decision levels of ≤ 16 ng/L in females and ≤ 34 ng/L in males.In-house quality control (QC) data gave overall %CV (for our two Abbott Architect analysers) of 12.9% (9.2 ng/L), 7.0% (51.0 ng/L), 5.8% (1213.9 ng/L) and 9.6% (6375.5 ng/L)