Table 2.
Comparison of stability between instruments of three methods: A. internal self mean ratio; B. ratios based on an external assay; and C raw instrument data. Internal self mean (A) is the most reliable. Using external ratios, (2C) is a close second, and raw readings, (2C) show the greatest deviation between instruments.
| Ratios N = 32 for all. | Mean z score | Median z score | Max z | Min z | |
| A | Ratios on internal self mean | ||||
| Rh. Sera 1:50 | 1.07 | 0.84 | 2.08 | 0.52 | |
| Rh. Sera 1:100 | 0.96 | 0.92 | 1.21 | 0.76 | |
| Rh. Sera 1:200 | 1.86 | 2.31 | 3.50 | 0.14 | |
| B | Ratios on real external mean (SRV/SFV mean and SFV/SRV mean) | ||||
| Rh. Sera 1:50 | 1.70 | 1.82 | 2.50 | 0.50 | |
| Rh. Sera 1:100 | 1.44 | 1.44 | 3.83 | 0.27 | |
| Rh. Sera 1:200 | 16.38 | 11.97 | 49.47 | 4.59 | |
| C | Raw inter instrument comparisons | ||||
| Rh. Sera 1:50 | 1.19 | 1.09 | 1.75 | 0.61 | |
| Rh. Sera 1:100 | 8.14 | 7.91 | 9.69 | 6.98 | |
| Rh. Sera 1:200 | 46.04 | 43.89 | 65.40 | 26.52 | |