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Coagulation Disorders Platelet Disorders
Table 1: Computation of a Theoretical Estimate of the Expected
Two strategies can be adopted in these cases: the selection of HLA-
Platelet Count Increment One Hour After The Transfusion of a
compatible donors from large registries of HLA-typed blood and bone
Given Number of Platelets Into a 75kg Male Patient
marrow donors
19,20
or the selection of compatible platelets by a cross-
matching procedure. In our hospital the latter strategy is able to
Variable 1 Platelet transfusion dose, e.g. 408 x 10
9
provide effective platelet support (post-transfusion increments greater
Variable 2 Patient’s blood volume (0.075 x kg bodyweight in males),
than 10,000 per microlitre) in three-quarters of cases.
21
Several reports
e.g. 0.075 x 75kg = 5.625l in the literature indicate that similar effectiveness can be obtained with
Correction factor Spleen ‘early’ sequestration of about one-third of
the HLA-typing approach. The choice between the two strategies
transfused platelets
depends on local organisation. The main discriminatory factor is the
Computation 408 x 10
9
platelets: 5.625l x 2/3 = 48,355 platelets
availability of a large panel of HLA-typed blood donors.
per microlitre
satisfactory increment, non-immune factors being considered Conclusions
responsible for the ineffectiveness in 88% of cases.
9
Another In spite of significant strides towards its resolution, platelet
investigation performed in 252 onco-haematology recipients detected refractoriness is still a transfusion complication that cannot be
the presence of platelet-reactive antibodies (mostly against human prevented or corrected in a relatively small, but not a negligible,
leukocyte antigens [HLAs]) in the serum of 113 patients (44.8%).
10
The proportion of recipients.
15
Therefore, it is necessary to perform
frequency of alloimmunisation is even higher in patients suffering from additional studies to ensure the prevention of primary and secondary
severe aplastic anaemia, as indicated by a study on 150 patients, 62% alloimmunisation to platelets and to improve the management and
of whom developed platelet alloimmunisation.
11
As expected, the resolution of clinical factors capable of reducing the effectiveness of
type of blood component represents an important factor related to the platelet support, not only for the clinical negative impact of
frequency of platelet alloimmunisation and alloimmune refractoriness. refractoriness, but also for its high cost. In the study reported by
Meehan et al.,
22
refractory and non-refractory patients had median
Supporting the evidence from the TRAP study,
5
an investigation from hospital stays of 35 days compared with 14.4 days and inpatient
Canada showed that the routine adoption of filtration leukoreduction hospital costs of US$103,956 compared with US$37,818, respectively.
was associated with a significant reduction in both platelet In our study,
20
in which 40 refractory patients received a mean of 14
alloimmunisation and alloimmune platelet refractoriness. Values cross-matched platelet transfusions over a period of 33 months, we
decreased from 19 to 7% and from 14 to 4%, respectively.
12
determined that each refractory patient generated an average expense
of €4,325 just for the solid-phase, disposable kit required for the
What Can We Do to Support Refractory Patients? selection of compatible platelets.
13
Labour costs should be added to
The resolution of non-immune causes of refractoriness belongs to the this sum.
general domain of global supportive therapy.
2,3,13–17
It can be difficult
to resolve a septic episode, correct coagulopathy secondary to Finally, despite the importance of all of the numbers and numerical
disseminated intravascular coagulation, reduce the size of an enlarged factors that have been discussed in this article (platelet dose, platelet
spleen or avoid using some drugs that have a negative impact on count increments, CCIs, etc.), the fundamental element in ensuring
platelet survival.
18
In these cases, the natural course of the disease can the best possible outcome of platelet support is the close co-operation
prevail over the therapeutic tools available to the clinician. Conversely, between a skilled transfusion medicine specialist and an experienced
a synergistic strategy between clinician and transfusion specialist can clinician able to identify clinical conditions associated with a high risk
re-establish the efficacy of platelet support in refractory patients of bleeding, patients with significant co-morbidity and those with early
whose refractoriness depends on platelet alloimmunisation. signs of haemorrhage.
23
■
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22 EUROPEAN HAEMATOLOGY 2007
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