Platelet flowcytometry: limitations and
possibilities
YASH PALAGRAWAL
Division of Laboratory Medicine, Massachusetts General Hospital, USA and Department of Clinical
Chemistry, University of Kuopio, Finland.
Introduction
Flow cytometry (FCM) hasmatured as an art and
discipline.The research applications ofFCM con–
tinue to develop at abrisk pace. The application of
FCM to newer clinical applications is decidedly
slower. This is inpart due either to reimbursement
issues whereby "experimental " tests cannot be
billed for or due to the lack of robustness/docu–
mented benefit of the assayproeecture required for
clinical decision making.
I
thus like to divide cli–
nical FCM tests into
3
levels where the first tier
comprises universally practiced clinical applica–
tions such as leukemia-lymphoma immunopheno–
typing. A considerable amount of published re–
views are available on these applications and the–
se applications are not further discussed. The se–
cond tier comprises potentially reimbursable app–
lications that are clinically useful if the possible
caveatsand limitations are understood.The infor–
mation regarding the clinical utility of this group
of tests is less weil defined in the literature and
some of the key issues involved in platelet analy–
sis are reviewed.The third tier comprises the gro–
upof interesting new clinical research applications
that are by definition of an experimental nature
with no established clinical utility (Tarnok et al,
1999;Drouvalakis et al, 1999).
For FCM laboratories the challenge then is to
continually survey the literature in search for ne–
wer diagnostic tests to better serve their patients
as weil as to push forward the FCM diagnostic ar–
mentarium. In this brief review I discuss some of
the key issues concerning analysis of reticulated
platelets and platelet antibodies.
1.1 Platelet flow cytometry:
In general, one has
to
be extreme!y careful when
using platelet FCM protocols for clinical applica–
tions (Michelson, 1996). One of the major diffi–
culties in the analysis of platelets for clinical use
is the problem of artifactual activation of plate–
lets. It is important to be aware of this especially
when using washed platelets or platelet rich plas–
ma as opposed to FCM of platelets from whole
blood. In this respect attempts have been made to
reach consensus on the issues concerning the col–
lection ofblood, choiceofanticoagulants, fixation
of specimens and data analysis by the European
WorkingGrouponClinical CellAnalysis (Schmitz
et al , 1998).
1.2Clinical indications formeasurement of
re–
ticulatedplatelets:
Thrombocytopenias arise from
three pathophysiologic mechanisms (Kienast and
Schmitz, 1990). Deficient production, accelerated
destruction or abnorma! pooling of platelets. Ab–
normal pooling could be due to hypersplenism in
the presence of splenomegaly. The usual clinical
problem in the evaluation of thrombocytopenias
is however the distinction between deficient pro–
ductian versus accelerated destruction ofplatelets.
This is best studied by an evaluation of the bone
marrowwhere the presence of an increased num–
bers of megakaryocytes would imply increased
peripheral blooddestruction ofplatelets and a pau–
city signify that the thrombocytopenia is due to a
decreased productian of megakaryocytes. Bone
marrows aspirates are however a painful proeectu–
re and thus there is a need for a non-invasive test
to identify the mechanism of thrombocytopenia.
Correspondence: Docent Yash PalAgrawal, Massachusetts General Hospital, Division of LaboratoryMedicine, Gray-Jackson
249, Fruit Street, Boston,MA 02114, USATel: 1-781-648-4645 E-mail :
92
Klinisk Kemi
i
Norden 4. 1999
