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False negative factor V Leiden assay following allogeneic stem cell transplant
K P Crookston1, R Henderson, W L Chandler
1Department of Laboratory Medicine, University of Washington, Seattle 98195, USA.
British Journal of Haematology
|March 21, 1998
Summary
A phenotypic test for activated protein C resistance correctly identified a patient's clotting disorder, while a genetic test yielded false negatives. This discrepancy was due to the patient receiving a stem cell transplant, altering blood cell DNA.
Area of Science:
- Hematology
- Clinical Genetics
- Molecular Diagnostics
Background:
- Activated protein C resistance (APC-R) is a common inherited thrombophilia.
- Genetic testing for Factor V (FV) Leiden mutation is standard for APC-R diagnosis.
- Stem cell transplantation can alter peripheral blood cell genetics.
Observation:
- A patient with suspected APC-R showed normal results on a DNA-based genetic test for the FV mutation.
- The patient's phenotypic assay (activity assay) correctly indicated the presence of an APC-R abnormality.
- Peripheral blood leukocytes were used for the genetic DNA analysis.
Findings:
- The genetic test produced a false-negative result due to the patient's recent stem cell transplant.
- The patient's leukocytes were donor-derived and lacked the specific FV gene defect.
- The phenotypic assay accurately reflected the patient's inherited APC-R, independent of donor cell chimerism.
Implications:
- Phenotypic assays remain crucial for diagnosing coagulation disorders, especially post-transplant.
- Genetic testing interpretation requires careful consideration of patient history, including transplantation.
- This case highlights the limitations of DNA-based testing in chimeric individuals.