Bethesda assay results in patient with AHA
| Sample dilution . | Residual FVIII (%) . | Inhibitor titer in this dilution . | Inhibitor titer (BU/mL) . |
|---|---|---|---|
| Neat | 27.6 | >2.00 | >2.0 |
| 2 | 38.5 | 1.38 | [1.38 × 2 = ] 2.8 |
| 4 | 45.4 | 1.14 | [1.14 × 4 = ] 4.6 |
| 8 | 50.3 | 0.99 | [0.99 × 8 = ] 7.9 |
| 16 | 57.7 | 0.79 | [0.79 × 16 = ] 12.6 |
| 32 | 71.6 | <0.50 | <16.0 |
| Sample dilution . | Residual FVIII (%) . | Inhibitor titer in this dilution . | Inhibitor titer (BU/mL) . |
|---|---|---|---|
| Neat | 27.6 | >2.00 | >2.0 |
| 2 | 38.5 | 1.38 | [1.38 × 2 = ] 2.8 |
| 4 | 45.4 | 1.14 | [1.14 × 4 = ] 4.6 |
| 8 | 50.3 | 0.99 | [0.99 × 8 = ] 7.9 |
| 16 | 57.7 | 0.79 | [0.79 × 16 = ] 12.6 |
| 32 | 71.6 | <0.50 | <16.0 |
The type 2 kinetics of the autoantibody gives the appearance that the inhibitor gets stronger the more it is diluted. For consistency, the dilution that gives closest to 50% residual FVIII (in italics) is used to determine the inhibitor titer that is reported to clinicians—in this case, 7.9 BU/mL.