The order of draw for a capillary blood collection is slightly different than the order of draw for a venous blood collection.
If capillary blood gases are ordered, they are drawn first to avoid introduction of room air as much as possible.
A specimen for blood count is collected before tubes containing other anticoagulants and additives. This is to ensure that the blood will not begin to clot before this specimen is collected; clots will affect the accuracy of the blood count.
The following order of draw is commonly used:
|Lavender top||EDTA||For hematology blood counts|
|Green top ||Lithium heparin||Tests that require a heparinized plasma sample|
Other tubes containing anticoagulants
|Red or gold top||Clot activator||Tests that require a serum sample|
|Red top |
|Tests that require a serum sample but clot activator and/or gel may affect test|