Specimen Collection Manual and Test Catalog

1 mL

• If the patient’s hematocrit (HCT) is >55%, the volume of anticoagulant in the tube must be adjusted. Contact a performing location for sodium citrate adjusted tubes or instruction for how to adjust the sodium citrate.
• When possible, use fresh venipuncture.
• Avoid prolong tourniquet time (< 1 minute) and hemolysis during collection as this will alter results.
• If indwelling catheter or butterfly collection device must be used, draw sample from a non-heparinized lumen or flush the line with 5 mL of saline and discard the first 10 mL of blood.
• Tubes should be >90% filled.
• Immediately mix gently after collection by inverting the tube end over end 5 to 6 times. Avoid vigorous mixing or additional inversion. Observe for the presence of clots or hemolysis and recollect if observed.

Centrifuge specimen immediately at designated time and speed to obtain platelet-poor plasma (<10,000/µL). Using a plastic pipette, carefully remove plasma from cells, avoiding platelet/buffy layer by leaving a thin layer of plasma on top the cells. The centrifuged plasma should be aliquoted (1 mL per aliquot) into clearly labeled polypropylene tubes. The number of tests ordered will determine the aliquots needed. Check the residual specimen for clot and if present discard sample and redraw specimen. If plasma is icteric, lipemic or hemolyzed a lab comment should be generated to notify staff. Freeze upright in non-thaw freezer.

Plasma (on or off cells): Room temperature 
Plasma off cells: Frozen on dry ice

Room temperature: 4 hours (no heparin therapy), 1 hour (heparin therapy) 
Frozen (plasma) -20°C: 2 weeks 
Frozen (plasma) -70°C: 6 months 
 

Clotted, hemolyzed, improperly filled tubes, improper anticoagulant ratio (HCT >55% and citrate not adjusted), refrigerated specimens, or stability exceeded.

Note: Specimen suspected of thawing in transport, indicated by slant in aliquot or specimen in lid of tube, will have testing performed, and the comment “interpret results with caution as thawing suspected” added to results.

21-38 seconds

Anticoagulation Impact on Coagulation Tests

APTT

PTT, Activated Partial Thromboplastin Time

Screening test used to assess the intrinsic and common clotting pathways. Prolongation of the APTT may be associated with bleeding and could indicate one or more deficiencies of plasma factors XII, XI, IX, X, V, II, or fibrinogen (only if less than 100 mg/dL), and/or a possible inhibitor (factor dependent or lupus anticoagulant) as well as a vitamin K deficiency (from dietary or intestinal reabsorption disorders). Diseases often associated with prolonged APTT include liver failure, lupus anticoagulant, and disseminated intravascular coagulopathy (DIC).

Medications may also prolong the APTT including heparin, direct Xa inhibitors, and direct thrombin inhibitors. A heparin nomogram using the APTT is available from the Geisinger pharmacy, but it is not recommended for heparin monitoring in patients unless there is interference with the unfractionated or low molecular weight heparin level.