Sodium citrate is the anticoagulant of
choice for studies of platelet function and morphology. The standard
concentration is 1 part 3.8% solutions to parts of blood, (Schalms; 2006) . For
coagulation studies a volume of blood is added to 1 volume of 109mmo1/l sodium
citrate solution (Ingram and Hills 1976). For erythrocyte sedimentation rate
(ESR), 4 volumes of blood are added to
1 volume of the sodium citrate solution (109mmol/L) and immediately mixed with
it (international committee for standardization in haematology: 1977). These are some
of the uses of sodium citrate.
Disadvantages of
Sodium Citrate;
1.
It
interferes with many chemical tests
2.
It
has a tendency to shrink cells
3.
Because
of a 10% dilution of blood,
sodium citrate is generally not used for complete blood count (CBC)
(Schalms; 2006)
For many years, citrate was the anticoagulant
preferred by most investigators undertaking platelet studies (Zelmanovic
et al, 1998), this is mainly
because sodium citrate causes less spontaneous activation of platelets in
vitro but EDTA does (Golanski et al; 1996). a high
concentration of sodium citrate in
blood samples decreases plasma
concentration of ionized calcium resulting in reduced platelet aggregation and fibrinogen binding. (Am Jvet Res; 2001).
When blood is collected into citrate,
there is initially little or no change in platelet shape and volume, however in citrate, platelets adopt a spherical shape and volume, however in citrate, platelets
adopt a spherical shape (Macey et al,
1999) and as in EDTA,
swell progressively over a period
of 1 -
2 hours (3-10% increase in volume
by impedance procedures, depending on
the concentration of sodium citrate used
(Threatte
el al; 1984; Bath; 1993 and Jackson and Carter,
1993) . citrate-base
anticoagulants have been used for their determination of platelet
indices in the ADVIA 120 (Macey
et al 1999 and Zelmanovic et al 1998)
they suggested that platelet sphering
may not be essential for the analysis. As cited from (Clin
Lab, 1990 ) analysis of the mean platelet volume (MPV)
showed significant lower values in the
citrated samples as compared to the same
examples in EDTA.