Add 0.45 mL of whole blood. Gently swirl to mix. Stain or fix immediately. Fixation Fixation of the blood with paraformaldehyde prior to staining inhibits spontaneous platelet activation. For clinical testing, fixing platelets can make the assay more manageable.
Fixation has an effect on activation-dependent platelet antibodies.
If fixation is not desired or possible, proceed to the next section, Direct Immunofluorescence Staining, and use fresh whole blood. 100 L of whole blood yields enough fixed blood for 20 tests. If additional fixed blood is required, prepare the appropriate number of tubes. Do not increase the volume of the blood or paraformaldehyde in the tube as this will increase the possibility of platelet aggregation. Fix platelets at 2 to 8 for a minimum of 2 hours.