(Clin
lab Haematol, 1990) showed that
EDTA amongst trisodium citrate, citrate
phosphate dextrose adenine and acid
citrate dextrose is the best anticoagulant for use in blood and blood
components is required (Thompson
et al, 1983) also has studied
and came out with a conclusion
that Na2EDTA appears to provide the best conditions of anticoagulation for both routine clinical and research laboratory measurement of the mean platelet volume (MPV).
They also
stated that this anticoagulant (Na2EDTA) inhibited platelet activation
but left the platelets in the normal discoid shape. Okada; 1999 stated that the
dipotassium salt of EDTA is the
preferred anticoagulant for platelet volume analysis in Europe and Japan, whereas in US and United Kingdom the tripotassium
salt of EDTA is more commonly used.
He
also stated that if blood is collected into EDTA, platelets quickly change shape from discs with a
2 -4µm diameter and a thickness of 0.45µm to spheres covered by long
thin filopodia. Threatte et al 1984 and Bath 1993 also
added that the sphering of
platelets in EDTA is initially so volumetric but almost immediately, their apparent size changes over 1-2
until a state of semi equilibrium is
reached (Okada; 1999). This led to the suggestion that EDTA is not a
suitable anticoagulant for platelet volume analysis (Rowani, 1986) . Okada, 1999 further stated
that if blood from certain individuals is anticoagulated with EDTA, the platelets aggregate, causing an apparent
thrombocytopenia to be recorded, Jackson and Carter 1993 also added that in
some but not all, cases may result from the
presence of agglutinating antiplatelet antibodies.
Nevertheless (Macey et al, 1999) cited
that EDTA has been used more
recently in several studies of platelet status,
the national committee for clinical laboratory methods also
recommends EDTA for full blood counts
and white blood cell differential
analysis ( National Committee for
clinical laboratory standards,
1996) . The international council
for standardization in
Haematology currently recommends
the dipotassium salt of EDTA as the
anticoagulant for full blood
counts and platelet analysis(International council for standardization
in haematology; 1993, and Lewis; 1999)
Note: Hedge
et al, 1991 stated that recent report suggested that storage of blood
in EDTA gave falsely elevated results
and they equally found out in their study that little difference occurred in the
values in blood anticoagulated in EDTA at
72 hours of storage