ISI Calibration results: TAS PT-NC and rTF/95
| Whole blood | Artificially depleted plasma | Individual coumarin plasma | Pooled coumarin plasma | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Centre | N | ISI | CV(b) | N | ISI | CV(b) | N | ISI | CV(b) | N | ISI | CV(b) | |
| The values shown are the ISI derived from the calibration slope b, the CV (%) of the calibration slope, and the number of samples used in the calibration (N). The “Overall” row gives the mean CV(b) and ISI at the 10 centres. The ISI CV% row gives the between centre CV (%) of the ISI. Mean ISI difference (whole blood ISI – lyophilised plasma ISI), corresponding confidence interval (CI) and p value are provided. | |||||||||||||
| *Significant displacement at the 1% level using Tomenson’s test.13 The absolute % INR deviations from the theoretical INR of 2.0 and 4.5, respectively, are given in parentheses. See World Health Organisation guidelines11 for further details; †ISI detected as outlying. | |||||||||||||
| CV, coefficient of variation; ISI, international sensitivity index; rTF/95, human recombinant international reference preparation. | |||||||||||||
| 1 | 74 | 1.07 | 4.4 | 78 | 0.92 | 3.5 *(10,12) | 79 | 0.86 | 4.3 *†(19,14) | 13 | 0.76 | 16.0† | |
| 2 | 75 | 1.29 | 2.6 | 79 | 1.03 | 2.2 | 77 | 0.99 | 4.1 | 13 | 0.97 | 9.2 | |
| 3 | 78 | 1.07 | 3.4 | 77 | 0.98 | 2.9 *(8,8) | 77 | 0.96 | 2.8 | 13 | 1.00 | 5.7 | |
| 4 | 77 | 1.16 | 3.2 | 79 | 1.00 | 1.7 | 79 | 0.99 | 2.0 | 13 | 0.97 | 4.9 | |
| 5 | 75 | 1.26 | 2.7 | 79 | 0.98 | 1.7 *(4,4) | 77 | 0.96 | 2.0 | 13 | 0.97 | 4.3 | |
| 6 | 79 | 1.17 | 3.6 *(10,11) | 79 | 0.90 | 2.3 | 79 | 0.96 | 2.4 | 13 | 1.02 | 4.0 | |
| 7 | 74 | 1.05 | 3.1 | 80 | 0.97 | 2.1 | 78 | 0.93 | 1.8 | 13 | 1.05 | 3.4 | |
| 8 | 74 | 1.06 | 3.8 | 79 | 1.04 | 2.0 | 78 | 1.00 | 1.9 *(5,3) | 13 | 0.98 | 3.7 | |
| 9 | 76 | 1.11 | 3.8 | 79 | 0.97 | 1.6 | 78 | 0.99 | 2.1 | 13 | 1.01 | 2.6 | |
| 10 | 75 | 1.08 | 4.7 | 80 | 0.99 | 2.0 *(5,6) | 78 | 0.95 | 1.7 *(6,4) | 13 | 0.96 | 6.1 | |
| Overall | 1.13 | 3.5 | 0.98 | 2.2 | 0.96 | 2.5 | 0.97 | 6.0 | |||||
| Mean ISI difference | 0.15 | 0.17 | 0.16 | ||||||||||
| CI | (0.09 to 0.21) | (0.11 to 0.23) | (0.08 to 0.24) | ||||||||||
| p Value | 0.0004 | 0.0001 | 0.001 | ||||||||||
| ISI CV (%) | 7.6 | 4.3 | 4.2 | 8.0 | |||||||||