Diagnostic score for heparin-induced thrombocytopenia
after cardiopulmonary bypass
A. LILLO-LE LOUE¨T,* P. BOUTOUYRIE,* M. ALHENC-GELAS,? C. LE BELLER,* I. GAUTIER,*
M. AIACH? and D. LASNE?1
*Centre Re ´gional de Pharmacovigilance and Clinical Pharmacology Unit, Ho ˆpital Europeen Georges Pompidou, Assistance Publique-Hopitaux de
Paris; and ?Laboratoire d’he ´matologie A, Ho ˆpital Europeen Georges Pompidou, Assistance Publique-Hopitaux de Paris and INSERM U428, Faculte ´
de Pharmacie, Paris, France
To cite this article: Lillo-Le Loue ¨t A, Boutouyrie P, Alhenc-Gelas M, Le Beller C, Gautier I, Aiach M, Lasne D. Diagnostic score for heparin-induced
thrombocytopenia after cardiopulmonary bypass. J Thromb Haemost 2004; 2: 1882–8.
Seealso MatthaiJrWH,CinesDB.Towardsa diagnosisofheparin-induced thrombocytopeniaaftercardiopulmonary bypass.Thisissue,pp 1879–81.
in nearly 3% of patients treated with heparin after cardiopul-
monary bypass (CPB). HIT carries a risk of severe thrombotic
complications, and must be diagnosed rapidly. To identify
simple criteria for estimating the probability of HIT after CPB,
we retrospectively analyzed the files of 84 patients with
suspected HIT after CPB and we analyzed the usefulness of
several variables collected at the time of HIT suspicion to
estimate HIT probability. HIT was confirmed in 35 cases and
ruled out in 49 cases, on the basis of a platelet increment after
and absence of other clear cause of thrombocytopenia. A
biphasic platelet count from CPB to the first day of suspected
HIT, an interval of ‡5 days from CPB to the first day of
suspected HIT, and a CPB duration of £118 min were
independent risk factors for HIT. These variables were
combined to create a post-CPB HIT probability score. The
score correctly identified 34/35 HIT patients and 28/49-non-
suspected after CPB, has very good negative predictive value
(97%). Prospective studies are required to confirm these
Keywords: cardiopulmonary bypass, clinical score, early
diagnosis, platelet count, ROC curve.
Patients who receive heparin after cardiopulmonary bypass
(CPB) are at risk of heparin-induced thrombocytopenia (HIT),
a severe complication of heparin treatment . Many patients
undergoing open heart surgery develop antibodies to platelet
factor 4 (PF4) complexed to heparin (H-PF4) (30 to >50%,
depending on the study) [2–4], owing to marked platelet
activation with massive PF4 release and to the use of high
heparin doses during CPB. These antibodies are commonly
considered responsible for HIT . However, less than 3% of
patients develop HIT during heparin treatment following CPB
[1,2,6,7]. Owing to the potential severity of HIT-related
thrombotic complications, early diagnosis is essential so that
heparin must be replaced rapidly with an alternative antico-
agulant (sodium danaparoid, hirudin or argatroban), even in
the absence of symptomatic thrombotic events [8,9].
HIT is suspected when the platelet count starts to fall
between 5 and 14 days after heparin introduction . Post-
with thrombocytopenia, secondary to hemodilution and plate-
let consumption . Also, many other potential causes of
thrombocytopenia may be present in critically ill patients
[11,12]. Current clinical scores for estimating the likelihood of
HIT do not take into account the particular situation repre-
sented by CPB [13–15]; in addition, most include platelet count
normalization after heparin discontinuation, and can therefore
be used only retrospectively [13,14]. Furthermore, biological
confirmation of HIT by immunologic and functional assays
 is often not available in time to guide clinical decisions.
HIT after CPB, we performed a retrospective analysis of the
files of 84 heparin-treated patients who developed thrombo-
cytopenia not attributable to CPB in our institution between
1997 and 2001. We evaluated the predictive value of several
variables that are readily available at the time when the
clinician suspects HIT, and analyzed their utility for estimating
Pharmacovigilance, Ho ˆ pital Europeen Georges Pompidou, 20–40 rue
Leblanc 75908 Paris cedex 15 France.
Tel.: +33 1 56093988;fax: +33 1 56093992;
A.Lillo-LeLoue ¨ t, Centre Re ´ gional de
1Present address: Laboratoire d’he ´matologie, Ho ˆ pital Necker, Paris
Received 16 January 2004, accepted 28 June 2004
Journal of Thrombosis and Haemostasis, 2: 1882–1888
? 2004 International Society on Thrombosis and Haemostasis
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? 2004 International Society on Thrombosis and Haemostasis