Table 1.
Platelet treatment–response types in relation to ADAMTS-13 activity and plasma von Willebrand factor (VWF) multimer distribution (expressed as VWF:CB/VWF:Ag ratio) in 26 disease episodes of idiopathic TTP
| Platelet response type | Number of episodesa | Days to platelets >140 × 109/l (from start PE, median, range) | Disease outcome | ADAMTS13 activity (%), mean (range) at | VWF ratio mean (range) at | Anti-ADAMTS13 IgG (μg/ml), mean (range) at | ||
|---|---|---|---|---|---|---|---|---|
| Diagnosis | Platelets >140 × 109/lb | Diagnosis | Diagnosis | Platelets >140 × 109/lb | ||||
| I | 4 | n.a. | All patients died of refractory disease on median day 9 from start PE | <10 (<3–9) | n.a. | 0.49 (0.26–0.54) | 196 (18–434) | 31 (14–62) |
| II | 13 | 7 (5–30) | Remissiond | <10 (<3–10) | 52 (25–113) | 0.89 (0.28–1.44) | 134 (11–800) | 16 (11–26) |
| III | 6 | 5 (3–6) | Remissiond preceded by a short-lasting normalisation of the platelet counte | <10 (<3–5) | 13 (4–29) | 0.48 (0.27–0.65) | 47 (31–61) | 21 (13–30) |
| IV | 3 | 5 (2–8) | Remissionf | <3 | <10 | 0.75 (0.48–0.89) | 51 (42–59) | Presentgh |
n.a. not applicable, PE plasma exchange
aTwenty-one episodes are newly diagnosed and five are first relapses, all occurring after a relapse-free interval of ≥1 year
bData represent the mean of two or three measurements on the first three consecutive days of platelets >140 × 109/l
cAnti-ADAMTS13 IgG levels in last plasma sample before death
dContinuing during follow-up of ≥1 year
eShort-lasting normalisation of the platelet count: platelets >140 × 109/l for≤10 days
fIn two episodes lasting >1 year, in one episode relapse after 6 months
gPersisting during follow-up of ≥1 year
hMeasured as anti-ADAMTS13 inhibitory activity