How to evaluate the influence of blood collection systems on the international sensitivity index. Protocol applied to two new evacuated tubes and eight coagulometer/thromboplastin combinations.
Previous reports indicate that the international sensitivity index (ISI) of coagulometer/thromboplastin combinations (measuring systems) may be influenced by blood collection systems. We applied a new protocol to assess the extent with which two new blood collection systems (evaluation tubes) influence the ISI of eight widely used measuring systems. The evaluation tubes were made of plastic and had draw volumes of 1.8 and 2.7 ml; citrate concentration was 0.109 M. Well-established collection tubes (from the same manufacturer)-which were made of siliconized glass with draw volume and citrate concentration of 4.5 ml and 0.105 M, respectively-served as control. Plasmas from 20 healthy subjects and 60 patients on oral anticoagulants, collected with the evaluation and control tubes, were tested for prothrombin time (PT) with the eight measuring systems. Plasmas collected with the control tubes were also tested with an international standard for thromboplastin. Results were used to calculate the ISIs of the measuring systems. These were then used to calculate the differences of the crossover international normalized ratio (INR) (i.e., the INR obtained with PT ratios of plasmas collected into the evaluation tubes and the ISI determined with plasmas collected into the control tubes). Overall, the differences were small but measurable, especially for the 2.7-ml draw evaluation tubes and with some of the measuring systems (mean difference, </=5.50%; mean relative deviation (MRD), </=5.82%). Although statistically significant, these differences are not clinically relevant as they are unlikely to affect decision making in drug prescription. In conclusion, the study shows that the evaluation tubes compare well with the control tubes from the same manufacturer. The protocol described here should be adopted for the evaluation of other blood collection systems.
Tripodi
Armando
A
Angelo Bianchi Bonomi, Hemophilia and Thrombosis Center, Department of Internal Medicine, University and IRCCS Maggiore Hospital, Via Pace 9, Milan 20122, Italy. armando.tripodi@unimi.it
Chantarangkul
Veena
V
Bressi
Caterina
C
Mannucci
Pier Mannuccio
PM
D000284:Administration, Oral; D000925:Anticoagulants / Q000008:administration & dosage; D001800:Blood Specimen Collection / Q000295:instrumentation* / Q000592:standards / Q000706:statistics & numerical data; D002985:Clinical Protocols; D006801:Humans; D019934:International Normalized Ratio / Q000295:instrumentation* / Q000592:standards / Q000706:statistics & numerical data; D013925:Thromboplastin
D000925:Anticoagulants; D013925:Thromboplastin