Laboratory Name Department ofPathology

AddressAutomated Hematology

Anti Factor Xa Heparin Therapeutic Range Comparison

Author(s), Name & Title / Heidi Hanes / Document Number / Effective Date
International QA/QC Coordinator / Pro62-05-SOP / 4-Aug-08
Review by / Heidi Hanes / Review date / 7 Feb 2012
Approved By / Name, Title / Signature / Date
SOP Annual Review / Name, Title / Signature / Date
Revision History / Version # [0.0] / Revision Date [dd/mm/yy] / Description (notes)
Distributed Copies to / Name (or location) / # of copies / Name (or location) / # of copies

SOP Number

Version

PURPOSENew lots of APtt reagent require studies before patient testing can begin. The current lot must be correlated with the new reagents to determine appropriate Therapeutic Heparin range. This procedure outlines all the steps it is necessary to follow when coagulation reagent lots are changed.

METHOD

/PrincipleThe heparin-responsiveness of APtt reagents is evaluated in vitrousing Anti-Factor Xa Chromogenics. Specifically, heparin concentrations of 50-150 plasma samples, derived from individuals receiving UFH (unfractionated heparin) therapy, are determined using a chromogenic anti-Factor Xa assay. Each result is then plotted against its corresponding APtt value, allowing construction of a heparin response curve. Therapeutic UFH levels are reported to be 0.3-0.7 IU/ml when the anti-Factor Xa assay is used and 0.2-0.4 IU/ml ifprotamine neutralization method is used. Correlation of measured heparin levels with the known APtt results allows determination of the therapeutic APtt range in context of the specific heparin-responsiveness to the APtt reagents and coagulation analyzer being used to monitor patients.

SPECIMENA 3.2% Sodium Citrate tube (blue top tube)is the recommended sample type for all of the assays to be performed. Tubes must be properly collected to insure the one to nine ratio for anticoagulant to blood. All blood samples are to be collected observing standard/universal precautions for venipunctures. Patients must be on known Heparin Therapy. Samples are processes following steps below. Patients should not be on Coumadin therapy and have no significant liver disease. When phlebotomizing the patient it is important to release the tourniquet as soon as possible. Allow the tubes to fill until there is no vacuum remaining. Unacceptable specimens include clotted, hemolyzed or quantity not sufficient (QNS). See below for processing and storage if needed.

Step / Action
1 / Centrifuge citrated sample at 1500g for 15 minutes.Preferably a refrigerated centrifuge if available.
2 /
  • Pipette off the plasma into another properly labeled plastic tube with a lid.
  • Make sure not to include any of the buffycoat or RBC layer

3 / Centrifuge again for 5 minutes at 1500g.
4 / Carefully pipette off plasma leaving any cells behind into another properly labeled plastic tube with a top.
5 /
  • If testing is delayed freeze plasma.
  • If stored at -20o C good for up to 14 days.
  • If stored at – 80o C good for up to 90days.
  • Thaw completelyand mixbefore running test.

MATERIALSAnti Factor Xa Reagent

Activated Partial Thromboplastin Time reagent.

All level of controls.

PROCEDURE

Step / Action
1 / If samples are frozen thaw completely before testing and mix.
2 / Perform APtt test on all samples. Perform all required QC
3 / Perform Anti Factor Xa test on all samples. Perform all required QC.
4 / Plot APtt results on the Y line and Heparin concentration on the X line on semi log paper.
5 / Correlate the heparin concentration (0.3-0.7 IU/ml) to the APtt results.

Results

Therapeutic Heparin range correlates to 0.3-0.7IU/ml using Anti- Factor Xa

method. Correlate the therapeuticrange to the APtt results. The APtt results

corresponding to the heparin levels 0.3-0.7IU/ml is the therapeutic heparin range.

Compare these results to previous lotnumber range. Notify appropriate

departments of any changes.

REFERENCE

  • Brill-Edwards P, Ginsberg J.S., Johnson M., Hirsh J. Establishing a therapeutic range for heparin therapy. Ann Intern Med 1993;199:104-109.

RELATED

DOCUMENTS

  • Coagulation Lot Change SOP
  • Heparin Sensitivity Curve SOP

APPENDIX

Appendix A: Heparin Response Curve

AUTHOR

Approval Signature:______Date: ______

Coagulation Lot ChangeSMILEPage 1 of 4

SOP number and version