Order of draw trainer

The sequence comes from the Clinical and Laboratory Standards Institute's own published statement of the order in GP41, not from a manufacturer wall chart. CLSI is the body the NHA CPT test plan names at knowledge statement k25 and again at task 2O. GP41 itself is not free to read, so nothing beyond CLSI's published article is restated here. Additive names, their mode of action and the tests each tube serves are taken from the WHO phlebotomy guidelines; note that WHO's own Table 2.3 sequence is based on the 2003 NCCLS consensus and is superseded, so this trainer follows CLSI for the order and WHO only for the additive detail. The capillary variant follows WHO section 7.1.3, which places the haematology specimen first, then chemistry, then blood bank. Colour codes vary between manufacturers, which is why each tube is labelled by its additive as well as its closure.

Drawing a coagulation panel, a CBC and a glucose means light blue, then lavender, then gray. Drawing EDTA before citrate is the classic error: both additives work by binding calcium, so EDTA carried into the citrate tube adds an uncontrolled anticoagulant to a test that depends on a precise citrate-to-blood ratio. CLSI's exception is the other half of the rule — only blood culture tubes, glass nonadditive serum tubes, or plastic serum tubes without a clot activator may be collected before the coagulation tube.