12th Congress of the European Hematology ... - Haematologica

12 th Congress of the European Hematology Association
0756
HEPARIN-INDUCED THROMBOCYTOPENIA: INCIDENCE, THROMBOTIC COMPLICATIONS
AND TREATMENT
E. Beggiato, F. Valeri, A. Borchiellini, C. Aguzzi, M. Bisone, F. Paciello,
P.C. Schinco, M. Boccadoro
Molinette Hospital, TORINO, Italy
Background. Heparin-induced thrombocytopenia (HIT) occurs in 0,5-
5% of heparin-treated patients, is due to anti heparin/PF4 antibodies
(HIT Ab) and significantly increases the risk of thrombotic events. HIT
related thromboses are reported in 17.5-45% of patients treated with
unfractionated heparin (UFH) and 0.6-5.9% of those treated with low
molecolar weight heparins (LMWH). Hallmark of HIT is the rapid
decline in platelet number (5-7 days) down to less than 50% of basal value.
It has recently been published that the presence of HIT even in the
absence of thrombocytopenia, raises the risk of thrombotic events;
therefore, it has been suggested in these patients to withdraw heparin
and start an alternative anticoagulant (AC) strategy even with no evidence
of thrombosis. Aims. Evaluation of: the incidence of thrombosis
in HIT patients, the response to alternative therapy and the role of a
additional pro thrombotic risk factors. Methods. 53 patients (mean age
67.2±13.9 yrs) with HIT Ab were evaluated, of whom 8 (15%) had
received UFH and 45 (85%) LMWH. In the UFH group, 5 (62,5%)
received prophylactic doses; in the LMWH group, 28 (62,2%) were on
prophylaxis. Heparin was stopped in all patients when HIT Ab were
detected. Additional risk factors were: polytrauma (3 patients), diabetes
(6), coronary artery disease (15), atrial fibrillation (4), cerebral vasculopathy
(4), cardiac valvular prosthesis (5), congenital thrombophilia (5), neoplasia
(8). Antiphospholipid antibodies (APA) were assayed in 66% of
patients. After heparin withdrawal, 11 patients (23%) were started on:
dermatan-sulphate (DS) (Mistral, Mediolanum, Italy), 7 (15%) DS + warfarin,
6 (13%) warfarin alone, 5 (11%) antiplatelet therapy, 1 (2%) defibrotide
+ warfarin; 15 subjects (32%) received no further anticoagulant
treatement. 2 patients died (4%); death was related to thrombosis in 1
case. Results. 6 patients (11%) in the LMWH group/prophylaxis developed
HIT-associated thrombosis (4 venous and 2 arterial) and 1 of them
consequently died, 2 of them had polytrauma, 1 diabetes. No patient
with cancer developed thrombosis. 4/35 subjects were positive for APA;
none developed thrombosis. In patients with thrombosis, mean platelet
fall was 60.2% of basal value; subjects asymptomatic for thrombosis had
a mean platelet fall of 53%. Conclusions. Thrombotic incidence was 11%
in our group. No correlation was found between thrombosis and APA,
neoplasia or other risk factors. No patient was treated with direct thrombin
inhibitors. Alternative AC therapy, expecially DS, showed efficacy
and safety. 32% of patiens received no further AC, without complications.
In the light of these results, the need for AC therapy with lepirudin,
a direct thrombin inhibitor that is approved worldwide for the
treatment of patients with HIT, seems questionable, expecially in those
without thrombosis. Risk factors leading to thrombosis in patients with
HIT remain to be elucidated.
0757
DETECTION OF SPECIFIC IGG ANTIBODIES IN HEPARIN-INDUCED THROMBOCYTOPENIA
TYPE II
K. Schallmoser, 1 C. Drexler, 1 E. Rohde, 1 A. Groselj-Strele, 1 S. Panzer, 2
G. Lanzer1 1 2 Medical University of Graz, GRAZ; Medical University of Vienna, VIENNA,
Austria
Background. Heparin-induced thrombocytopenia type II (HIT II) is
caused by antibodies (ab) against Heparin/platelet factor 4 (HPF4) complex.
Commercially available ELISAs detect ab of IgG-, IgA- and IgMclass
without differentiation whereas it is assumed that only IgG ab are
responsible for typical clinical sequels. Aims. This study was performed
to compare detection of IgG ab with two different serological assays in
patients with surgical and medical diagnoses suspected for HIT II. Materials
and Methods. Serum samples of 165 patients (64 surgical, 30 male;
mean age 65.5 years, range 1.4-90.3; 101 medical. 41 male; mean age 66.3
years, range 2.6-96.6) with clinically suspected HIT II were tested by a
gel particle test (ID-PaGIA H/PF4, DiaMed, Cressier, s/Morat, Switzerland)
and by ELISA (GTI PF4 HAT45, GTI, Waukesha, WI, USA) using
combined anti-IgG/A/M and an anti-IgG conjugate (GTI) only. Results.
The gel particle test revealed positive reactions in 39/165 patients, 35/39
had positive IgG/A/M ELISA reactions, and IgG ab were detected in
25/35 cases. In the group of patients with negative gel test results (n=126)
we found 42 patients positive in the IgG/A/M ELISA and 12/42 had IgG
282 | haematologica/the hematology journal | 2007; 92(s1)
ab. A positive correlation between the gel particle test and detection of
IgG ab was found (phi =0.556; p