1. Scenario F/ 86 Autoimmune hypothyroidism since 2001
Spontaneous bruising for 2 wks: neck, upper limbs, thigh, flank
Increasing neck swelling with respiratory arrest on day 1, intubated and transferred to ICU

2. Scenario APTT level – 77 second PT, platelet level – normal
Hb 6.6 (prev Hb 12.4)
Mixing test
APTT s
APTT (1:1) mix s
APTT (1:1) mix 37C 1 hr s

3. Cause of bleeding tendency?
Ddx:
Specimen contaminated by heparin
Lupus anticoagulant
Acquired inhibitors of the intrinsic factor pathway (VIII, IX, XI, XII)
Acquired von Willebrand disease

4. Scenario Factor VIII inhibitor level: 40 Bethesda Unit
Factor VIII level: 5 U/dL (Normal: )
Dx: Acquired hemophilia A due to inhibitor to factor VIII

5. Scenario
Given recombinant factor VIIa (Novo-seven) 4800mcg (90mcg/kg) iv bolus for total 8 dose during first 1 week of admission

6. Prednisolone 40mg/d + MMF 1g bd since 12/6/07
Factor VIII inhibitor level
40 BU
14 BU

7. Diagnostic tests – Mixing test
Identify whether inhibitor is present, but not inhibitor’s specificity
Step 1: Establish whether a circulating anticoagulant / inhibitor is present
Mix equal amounts of the patient’s plasma (containing and normal plasma
Measure APTT
Immediately
After incubation at 37 degrees for 1 to 2 hrs

8. Diagnostic tests – Mixing test
Immediate result
Correction of the prolonged APTT  factor or vWF deficiency
Persistent prolongation of APTT  inhibitor is present
Post-incubation result
Some inhibitor has delayed reactivity: APTT corrected immediately after mixing, but prolong again after incubation

9. Diagnostic tests – Mixing test
Step 2: Differentiate whether the circulating anticoagulant is an autoAb directed against a clotting factor / against cell membrane phospholipids
Add a source of phospholipid to the mixed plasma
Correction of APTT  autoAb against phospholipid
Persistent prolongation of APTT  autoAb against a clotting factor  perform the Bethesda assay

10. Diagnostic tests – Bethesda assay
Use: Quantifies the antibody titre
Method:
Incubate serial dilutions of patient’s plasma with normal plasma at 37 degrees for 2 hrs
Measure the residual FVIII activity
Definition: Number of dilution of patient’s plasma that result in 50% decrease in factor VIII activity
Higher BU  more inhibitor

11. Acquired Haemophilia

12. Acquired vs Congenital
No genetic inheritance pattern
M = F
Median age of presentation: 60 – 70 yrs
Bleeding pattern
Congenital – haemathroses
Acquired – soft tissue bleeding, muscle bleeding, haematuria, GI bleed
May present with persistent bleeding after a surgical procedure
Increased mortality

13. Acquired hemophilia Most common is against factor VIII
Others: factor v, vii, ix, x, xi, xiii

14. Factor VIIIa as a cofactor to IXa
Forms a complex with factor X, IXa, phospholipid surface
Increase the catalytic efficiency of factor IXa toward factor X (X  Xa)
Blood Reviews 2004; 18:1-15

15. Anti FVIII Ab prevents F VIII from interaction with its 4 partners – phospholipid surface (PLs), vWF, factors IX, X
Thromb Haemost 2005; 94:760-9

16. 172 patients identified in 2 yrs
Incidence: 1.48 per million per yr
Median age 78 yrs
Male 43% Female 57 %

17. Presenting characteristics – Age
% with underlying diagnosis
< 40 yrs – 100%
40-59 yrs – 55%
60-79 yrs – 42%
> 80 yrs – 23%

18. Disease associations
No (%)

19. Presenting characteristics – Levels of FVIII

20. Presenting characteristics – Bleeding
34% patients do not require haemostatic treatment
2 patients were asymptomatic

21. Fatal bleeding
Bleeding is the cause of death in 9.1% at a median of 19 days
Fatal bleeding can occur up to 5 mths after presentation if the inhibitor is not eradicated.
Factor VIII and inhibitor titre at presentation were not useful for predicting the severity of bleeding events.
Median inhibitor level was similar for those with fatal bleed and those who require no haemostatic therapy

22. Management options

23. Goal of Treatment Control bleeding Eradication of the inhibitor
Agents that increase F VIII levels
DDAVP
Factor VIII concentrates
F VIII bypassing agents
Activated prothrombin complex concentrates
Recombinant factor VIIa
Eradication of the inhibitor
Immunosuppression
Biological therapy

24. Increase F VIII levels DDAVP Factor VIII concentrates
Release endogenous FVIII protein
Transient rise in factor VIII
For patients with very low inhibitor titres <3 BU
Factor VIII concentrates
Transient - High Ab titres rapidly inactivate FVIII concentrates
For patients with low inhibitor titres <5 BU
FFP and cryoprecipitate do not contain sufficient FVIII to overcome the inhibitor  rarely effective

25. F VIII bypassing agents - aPCC
For patients with severe bleeding or inhibitor titre > 5 BU
Each vial contains
Factor IX, X, II
F IXa generate additional F VIIa
Antithrombin III
Inactivates F Xa and thrombin
Heparin
Minimal amount, to forestall risks of thrombosis and DIC
Low levels of factors V and VII
aPCC 75 units/kg every 8-12 hrs
Max dose of 200 units/kg within a 24 hr period
Risk of thromboembolism, MI, DIC

26. Recombinant factor VIIa
Brand-name: Novo-Seven
Mechanism
Form a complex with tissue factor  local thrombin generation
Activate F X (independent of tissue factor) on the surface of activated platelets
Dose
90 – 120 microgram/kg every 3 hrs
Short t ½ 2.7 hrs
Bolus dose, given over 2-5 min

27. Recombinant factor VIIa
At high dose, rFVIIa binds activated platelet independent of TF
Localization activity -> relative lack of thrombotic complication

28. rFVIIa 74 bleeding episodes in 38 patients with acquired haemophilia
Median dose 90 microgram/kg every 2-6 hrs
Median no of doses: 28 per episode
Median duration of treatment 3.9 days
Response
As initial therapy: 100% response rate
Salvage therapy:
75% good response rate
17% partial response
8% poor control of bleeding
Those patients who did not respond within 24 hrs were unlikely to respond if rVIIa was continued.
Thromb Haemost 1997; 78:1468-7
Define response

29. aPCC vs rVIIa No direct comparison studies APCC rVIIa
Adv of dosing every 8-12 hrs
Cost $0.8/units. i.e. 70 units/kg q8hr = $ 2,800 q8hr
Thrombosis risk
rVIIa
Recombinent protein, less likely to be contaminated with infectious agents
Infused every 2-3 hrs
More costly
$ 4, per vial (1.2 mg) -- $20,000 for each injection

30. Inhibitor elimination
Prednisolone 1 mg/kg/day
Inhibitor abolition in approx 30% of patients
+ Cyclophosphamide 1 to 2 mg/kg
Increase response rate to 60-70%
Slow response in 3-6 wks, some may have a prolonged response time of mths
Relapse is not uncommon
Cyclosporin
Use alone or with prednisolone
Esp effective in patients with underlying SLE

31. Outcome – UK study Outcome between different treatment gps
144/151 (95%) were treated with immunosuppression
Steroid alone – 40 patients (26%)
Concomitant steroids and cytotoxics – 48 patients (31%)
The patient gp treated with steroids alone had a lower median inhibitor titre (p <0.01) and factor VIII level (not sig)
But neither the inhibitor titre and factor VIII level were associated with outcome

32. Outcome – Inhibitor eradication
Complete remission – defined as
Normal factor VIII level, undetectable inhibitor level
Immunosuppression stopped or reduced to doses used before acquired haemophilia develop
Without relapse

33. Outcome – Inhibitor eradication
102/144 patients (71%) achieve CR
Mean time to remission
All patients – 57 days
Steroids alone – 49 days
Steroids + cytotoxics – 39 days (P = 0.51)
No difference between steroid gp and steroid + cytotoxic gp (irrespective of treatment order)

34. Outcome – Inhibitor relapse
18 / 90 patients (20%) had a relapse
Median time to relapse
7.5 mths after stopping immunosuppression (range 1 to 14 mths)
Out of the 18 patients
10 patients (56%) achieve a second CR
4 patients (22%) has inhibitor eradicated and factor VIII normalized, but immunosuppression could not be stopped without a relapse
4 patients (22%) could not achieve a second remission

35. Outcome – Survival
No difference between steroid gp and steroid + cytotoxic gp (irrespective of treatment order)
Median survival time between presentation and death
Steroid alone – 767 days
Steroids + cytotoxics – 975 days

36. Outcome -ve predictors of outcome Not predictors Age
Underlying diagnosis (except for postpartum)
Factor VIII level, inhibitor titre at diagnosis

37. Conclusions Acquired Hemophilia A
May not have bleeding, but fatal bleeding remains a risk if inhibitor not eradicated.
No clinical or laboratory features identify the high-risk patients
All patients advised immuno-suppressed once diagnosed
Tx with steroid or steroid + cytotoxics

38. Thanks