International Normalized Ratio (INR), coagulation factor activities and calibrated automated thrombin generation - influence of 24 h storage at ambient temperature
ABSTRACT International Normalized Ratio (INR) measurements are used to monitor oral anticoagulation therapy with coumarins. Single coagulation factor activities and calibrated automated thrombin (CAT) generation are considered as more advanced methods for evaluating overall haemostatic capacity. The aims were to assess the variability of INR, coagulation factor activities, and CAT, during 24 h of storage of blood samples at ambient temperature. A total of 24 patients on stable coumarin treatment were followed prospectively for 6 weeks. INR was analyzed at 0, 6 and 24 h after blood sampling and 1-stage clotting activity of coagulation factors II, VII, IX, and X as well as CAT generation was recorded after 0 and 24 h respectively. Statistical analyses included Bland-Altman plot, 95% limits of agreement, and a variability test using a mixed effect model. The level of INR remained statistically unchanged from 0 to 6 and 24 h of storage. Coagulation factor activities and CAT revealed no significant difference induced by 24 h of storage, although the limits of agreement were wide. Patients' individual INR, coagulation factor activities, and CAT generation were not significantly influenced by 24 h storage of blood samples, but for the CAT generation analyses a trend toward time dependency was detected.
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ABSTRACT: We designed this study to assess the effect of storage time and temperature on the international normalized ratio (INR) levels and plasma activities of vitamin K-dependent, clotting factors. A total of 100 subjects, comprising 34 healthy controls, 33 patients with liver cirrhosis and 33 patients on long-term coumarin therapy were enrolled. After centrifugation of collected specimens, aliquots of plasma were stored at room temperature (20 -22 degrees C), refrigerated at 2-6 degrees C and frozen at -40 degrees C. Determinations of INR and plasma activities of clotting factors II, VII, IX and X were performed immediately after sampling (0 time) and after 6, 12 and 24 h. We found no significant change of either INR levels or plasma activity of any of the studied clotting factors up-to 24 h at different studied temperatures (p >0.05). Our data demonstrates that clinical specimens for determination of INR levels and plasma activities of factors II, VII, IX and X are acceptable for testing for up-to 24 h whatever may be the temperature of storage.Hematology 10/2004; 9(5-6):333-7. DOI:10.1080/10245330400010646 · 1.19 Impact Factor
Article: Phenotyping the clotting systemThrombosis and Haemostasis 12/2000; 84(5):747-51. · 5.76 Impact Factor
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ABSTRACT: The quality of oral anticoagulant therapy management with coumarin derivatives requires reliable results for the prothrombin time/International Normalized Ratio (PT/INR). We assessed the effect on PT/INR of preanalytical variables, including ones related to off-site blood collection and transportation to a laboratory. Four laboratories with different combinations of blood collection systems, thromboplastin reagents, and coagulation meters participated. The simulated preanalytical variables included time between blood collection and PT/INR determinations on samples stored at room temperature, at 4-6 degrees C, and at 37 degrees C; mechanical agitation at room temperature, at 4-6 degrees C, and at 37 degrees C; time between centrifugation and PT/INR determination; and times and temperatures of centrifugation. For variables that affected results, the effect of the variable was classified as moderate when <25% of samples showed a change >10% or as large if >25% of samples showed such a change. During the first 6 h after blood collection, INR changed by >10% in <25% of samples (moderate effect) when blood samples were stored at room temperature, 4-6 degrees C, or 37 degrees C with or without mechanical agitation and independent of the time of centrifugation after blood collection. With one combination of materials and preanalytical conditions, a 24-h delay at room temperature or 4-6 degrees C had a large effect, i.e., changes >10% in >25% of samples. In all laboratories, a 24-h delay at 37 degrees C or with mechanical agitation had a large effect. We observed no clinically or statistically relevant INR differences among studied centrifugation conditions (centrifugation temperature, 20 degrees C or no temperature control; centrifugation time, 5 or 10 min). We recommend a maximum of 6 h between blood collection and PT/INR determination. The impact of a 24-h delay should be investigated for each combination of materials and conditions.Clinical Chemistry 03/2005; 51(3):561-8. DOI:10.1373/clinchem.2004.043174 · 7.77 Impact Factor