Proper specimen collection presumes correct technique and accurate timing when necessary. Although blood tests are common procedures for many patients, fear of needles or sight of blood may cause fear or anxiety. Always assess the patient for these factors and provide patient education, reassurance, and support. Most hematology tests use liquid ethylenediaminetetraacetic acid (EDTA) as an anticoagulant. Tubes with anticoagulants should be gently but completely inverted end over end 7–10 times after collection. This action ensures complete mixing of anticoagulants with blood to prevent clot formation. Even slightly clotted blood invalidates the test, and the sample must be redrawn.
For plasma coagulation studies, such as prothrombin time (PT) and partial thromboplastin time (PTT), the tube must be allowed to fill to its capacity or an improper blood-to-anticoagulant ratio will invalidate coagulator results. Invert the tube end over end 7–10 times to prevent clotting.
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