MLAB 1227Coagulation Keri BrophyMartinez

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MLAB 1227-CoagulationKeri Brophy-Martinez

• Preanalytical Issues in Coagulation Testing

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Objectives

• Describe special precautions regarding specimen
  collection and processing for coagulation testing
  and determine the appropriateness of specimens.

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Sample Collection

• Anticoagulant of choice
• 3.8 or 3.2 Sodium Citrate
• Anticoagulant/blood ratio is critical (19)
• Exact amount of blood must be drawn. No short
  draws are acceptable, this will falsely increase
  results due to presence of too much anticoagulant
• Purpose of the anticoagulant is to bind or
  chelate calcium to prevent clotting of specimen

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Sample Collection

• Sidenote Samples with High hematocrits
• NCCLS recommends adjusting anticoagulant ratio
  for patients with hematocrits exceeding 55
• High hematocrits may cause falsely increased test
  results due to an over- anticoagulated sample
• Formula correction achieves a 40 hematocrit

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Formula High Hematocrits

• 60_________ x 2.7 ml draw size tube
• 100- Patients hematocrit
• Whole Blood Volume to Add to 6 ml red top tube

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Site Selection

• Untraumatic venipuncture is required
• Fingersticks/Heelsticks are not allowed
• Indwelling IV line draws are discouraged
• Contain heparin
• Falsely increased results

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Order of Draw

• Evacuated tube system
• Blue top is 1st or 2nd tube.
• If 2nd tube drawn, 1st top must be anticoagulant
  free (i.e. red top)
• Butterfly system
• Discard tube must be utilized
• Why?
• To avoid clotting
• To rid specimen of air in the tubing which can
  cause an inaccurate blood-anticoagulant ratio

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Storage Requirements

• Prothrombin Time PT
• Uncentrifuged or centrifuged with plasma
  remaining on top of cells in unopened tube kept
  at 2-4 oC or 18-24 oC must be tested within 24
  hours of collection
• Activated Partial Thrombin Time APTT
• Uncentrifuged or centrifuged with plasma
  remaining on top of cells in unopened tube kept
  at 2-4 oC or 18-24 oC must be tested within 4
  hours of collection

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Storage Requirements

• Other Assays
• Fibrinogen, Thrombin Time, Factor Assays
• Centrifuged with plasma remaining on top of cells
  in unopened tube kept at 2-4 oC or 18-24 oC must
  be tested within 4 hours of collection

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Storage Requirements

• Other general notes
• Perform coagulation tests ASAP
• Specimen may deteriorate rapidly (especially
  factors V and VIII)
• If the testing is not completed within specified
  times, plasma should be removed from the cells
  and placed in a frost free freezer
• - 20 oC for two weeks
• -70 oC for six months

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Transportation of Specimen

• Send specimen on ice OR deliver to lab ASAP
• Separate cells from plasma immediately via
  centrifugation

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Common Collection Problems
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Terms

• Platelet Poor plasma
• lt10 x 10 9 /L
• Specimen has been centrifuged for 15 minutes _at_
  2500 x g
• Platelet-Rich plasma
• Used in platelet aggregation studies
• 200-300 x 10 9 /L
• Specimen has been centrifuged for 10 minutes _at_
  200 x g