MLAB 1227-Coagulation Keri Brophy-Martinez

1. MLAB 1227-CoagulationKeri Brophy-Martinez Preanalytical Issues in Coagulation Testing

2. Objectives Describe special precautions regarding specimen collection and processing for coagulation testing and determine the appropriateness of specimens. State the type of anticoagulant tube used for coagulation testing. Discuss the function of the sodium citrate anticoagulant in coagulation testing. Recognize the appropriate order of draw in terms of coagulation testing. Cite storage requirements for the prothrombin and activated prothrombin time assays. Define platelet poor plasma. Define platelet rich plasma. State the purpose of the blood to anticoagulant ratio in the sodium citrate tube.

3. Sample Collection Anticoagulant of choice 3.8% or 3.2% Sodium Citrate 3.2 % Preferred as the standard measure due to stability and closeness to the plasma osmolality Anticoagulant/blood ratio is critical (1:9) Exact amount of blood must be drawn. No short draws are acceptable, this will falsely increase results due to presence of too much anticoagulant CLSI guideline is +/- 10 % of fill line Purpose of the anticoagulant is to bind or chelate calcium to prevent clotting of specimen

4. Sample Collection Sidenote: Samples with High hematocrits NCCLS recommends adjusting anticoagulant ratio for patients with hematocrits exceeding 55% High hematocrits may cause falsely prolonged test results due to an over- anticoagulated sample Formula correction achieves a 40% hematocrit

5. Correction Formula: High Hematocrits (1.85 x 10 -3)* (100-Hct)*V= C Where: C= volume of sodium citrate V=volume of whole blood drawn Hct= patient’s hematocrit Example: Patients Hct= 63% V= 5 mL (1.85 x 10 -3)* (100-63)*5= C (1.85 x 10 -3)* (37)*5= 0.34 mL

6. Site Selection Untraumatic venipuncture is required Traumatic venipunctures release tissue factor and initiate coagulation Fingersticks/Heelsticks are not allowed Indwelling IV line draws are discouraged Contain heparin Falsely increased results

7. 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

8. 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

9. 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

10. 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

11. Transportation of Specimen Send specimen on ice OR deliver to lab ASAP Separate cells from plasma immediately via centrifugation

12. Common Collection Problems

13. Common Collection Problems (con’t)

14. Terms Platelet –Poor plasma (PPP) <10 x 10 9 /L Specimen has been centrifuged for 15 minutes @ 2500 x g Why is PPP essential? Contains platelet factor 4(heparin neutralizer) Contains phospholipid (affects lupus anticoagulant and factor assay testing) Contains proteases (affect testing for vWF)

15. Terms Platelet-Rich plasma(PRP) Used in platelet function studies 200-300 x 10 9 /L Specimen has been centrifuged for 10 minutes @ 200 x g