Heparin is added into the blood collection vessel. Heparin directly has the effect of antithrombin, which can prolong the coagulation time of the specimen. Excessive heparin will cause leukocyte aggregation and cannot be used for leukocyte counting. Because it can make the background of blood slice dyed light blue, the lab use test tube is not suitable for leukocyte classification.
Green cap test tubes is mainly used for whole blood, plasma the green sodium haparin blood collection tubes is used for erythrocyte fragility test, blood gas analysis, hematocrit test, ESR and universal biochemical determination.