Ig isotype and IgG subclass distribution, titer, and affinity of anti-FVIII antibodies in 81 patients with AHA
| Isotype or subclass . | Positive screening, n (%) . | Titer in positive patients, median (IQR) . | Apparent affinity (main cluster) . | Apparent affinity (second cluster, if detected) . | ||
|---|---|---|---|---|---|---|
| n . | KA [M−1] − median (IQR) . | n . | KA [M−1] − median (IQR) . | |||
| IgG1 | 71 (88) | 1:640 (1:320-1:2560) | 70 | 1.4 × 1010 (0.8 × 1010-4.2 × 1010) | 15 | 7.5×107 (4.5×107-9.4×107) |
| IgG2 | 62 (77) | 1:80 (1:40-1:320) | 40 | 1.9 × 109 (1.0 × 109-3.2 × 109) | 2 | 5.7×107 (4.8×107-6.6×107) |
| IgG3 | 33 (41) | 1:80 (1:40-1:320) | 19 | 1.3 × 1010 (0.5 × 1010-1.8 × 1010) | 5 | 9.7×107 (6.8×107-9.9×107) |
| IgG4 | 79 (98) | 1:5120 (1:1280-1:20 480) | 77 | 5.8 × 1010 (2.4 × 1010-1.3 × 1011) | 6 | 3.8×109 (2.9×109-5.2×109) |
| IgA | 37 (46) | 1:80 (1:40-1:160) | 18 | 1.7 × 109 (0.9 × 109-4.6 × 109) | 8 | 5.4×107 (4.6×107-5.5×107) |
| IgM | 7 (9) | 1:80 (1:40-1:80) | 0 | n/d | 0 | n/d |
| Isotype or subclass . | Positive screening, n (%) . | Titer in positive patients, median (IQR) . | Apparent affinity (main cluster) . | Apparent affinity (second cluster, if detected) . | ||
|---|---|---|---|---|---|---|
| n . | KA [M−1] − median (IQR) . | n . | KA [M−1] − median (IQR) . | |||
| IgG1 | 71 (88) | 1:640 (1:320-1:2560) | 70 | 1.4 × 1010 (0.8 × 1010-4.2 × 1010) | 15 | 7.5×107 (4.5×107-9.4×107) |
| IgG2 | 62 (77) | 1:80 (1:40-1:320) | 40 | 1.9 × 109 (1.0 × 109-3.2 × 109) | 2 | 5.7×107 (4.8×107-6.6×107) |
| IgG3 | 33 (41) | 1:80 (1:40-1:320) | 19 | 1.3 × 1010 (0.5 × 1010-1.8 × 1010) | 5 | 9.7×107 (6.8×107-9.9×107) |
| IgG4 | 79 (98) | 1:5120 (1:1280-1:20 480) | 77 | 5.8 × 1010 (2.4 × 1010-1.3 × 1011) | 6 | 3.8×109 (2.9×109-5.2×109) |
| IgA | 37 (46) | 1:80 (1:40-1:160) | 18 | 1.7 × 109 (0.9 × 109-4.6 × 109) | 8 | 5.4×107 (4.6×107-5.5×107) |
| IgM | 7 (9) | 1:80 (1:40-1:80) | 0 | n/d | 0 | n/d |
Screening was done twice at a dilution of 1:20 and considered positive (positive screening) if at least one test yielded a differential optical density ≥ cutoff. Samples with positive screening were subjected to titer titration, starting at a dilution of 1:20 and continuing in 1:2 dilution steps (titer in positive patients). Only samples with titers ≥1:80 were subject to assessment of apparent affinity. If samples exhibited a bimodal affinity distribution, the lower KA was assigned to a second antibody cluster
IQR, interquartile range; KA, affinity constant; n/d, not determined.