EDTA – A STUDY BY MCSCHINE, RL. SIBINGA, S. BROZOVIC B

(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