Table 1.
Main CSF parameters after lowering serum IgG level by plasma exchange (PLEX)
| [IgGserum] | True ITS (IgGLoc) (mg/L) | [IgGCSF] (mg/L) | IgG index | Q IgG (×10−3) | IgGLoc (Lim) (mg/L) | True IFIgG (%) | Estimated IFIgG (%) |
|---|---|---|---|---|---|---|---|
| Before PLEX | 0 | 23 | 0.5 | 2.3 | 0 | 0 | 0 |
| 1 | 24 | 0.5 | 2.4 | 0 | 4.2 | 0 | |
| 5 | 28 | 0.6 | 2.8 | 0 | 17.9 | 0 | |
| 25 | 48 | 1.0 | 4.8 | 13.2 | 52.1 | 27.5 | |
| 50 | 73 | 1.5 | 7.3 | 38.2 | 68.5 | 52.4 | |
| −20% | 0 | 18.4 | 0.5 | 2.3 | 0 | 0 | 0 |
| 1 | 19.4 | 0.5 | 2.4 | 0 | 5.2 | 0 | |
| 5 | 23.4 | 0.6 | 2.9 | 0 | 21.4 | 0 | |
| 25 | 43.4 | 1.1 | 5.4 | 15.5 | 57.6 | 35.9 | |
| 50 | 68.4 | 1.7 | 8.6 | 40.5 | 73.1 | 59.3 | |
| −50% | 0 | 11.5 | 0.5 | 2.3 | 0 | 0 | 0 |
| 1 | 12.5 | 0.5 | 2.5 | 0 | 8.0 | 0 | |
| 5 | 16.5 | 0.7 | 3.3 | 0 | 30.3 | 0 | |
| 25 | 36.5 | 1.5 | 7.3 | 19.1 | 68.5 | 52.4 | |
| 50 | 61.5 | 2.5 | 12.3 | 44.1 | 81.3 | 71.7 | |
| −90% | 0 | 2.3 | 0.5 | 2.3 | 0 | 0 | 0 |
| 1 | 3.3 | 0.7 | 3.3 | 0 | 30.3 | 0 | |
| 5 | 7.3 | 1.5 | 7.3 | 3.8 | 68.5 | 52.4 | |
| 25 | 27.3 | 5.5 | 27.3 | 23.8 | 91.6 | 87.3 | |
| 50 | 52.3 | 10.5 | 52.3 | 48.8 | 95.6 | 93.3 |
Simulation with various levels of true ITS (from null to 50 mg/L). Q IgG_basal = Q mean is used for the sake of clarity. Starting parameters: Q Alb = 5 × 10−3; Q IgG_basal = 2.3 × 10−3; Q Lim(3SD) = 3.47 × 10−3; [IgGserum] = 10 g/L. Results initially abnormal or becoming abnormal after PLEX are in bold. In the event of null ITS, IgG index remains normal throughout PLEX procedures, whereas if ITS is raised to 5 mg/L (see Fig. 7), IgG index becomes abnormal when basal [IgGserum] is reduced by 50%. Estimated IFIgG increases from 0% to 52% for a 90% decrease in basal [IgGserum].