PCR for Antigen Receptor Rearrangements (PARR)

The PCR for Antigen Receptor Rearrangements (PARR) test is a molecular diagnostic technique that helps differentiate between reactive (non-neoplastic) and neoplastic lymphoid proliferations in veterinary patients. By analyzing the rearrangements in T-cell and B-cell antigen receptor genes, PARR can identify clonal populations indicative of lymphoma or leukemia. This test is particularly useful when cytology or histopathology results are inconclusive, providing a definitive assessment of lymphoid clonality and supporting a precise diagnosis.

Test name

PCR for Antigen Receptor Rearrangements (PARR)

Test Code

1013

Section

Cancer Diagnostics

Species

Canine

Specimen

Blood and Bone Marrow:

1. Submit at least 500 µL (0.5 ml) of blood or bone marrow in an EDTA tube. Additionally, you may send 4-5 highly cellular bone marrow slides, though peripheral blood slides are not needed.
2. If available, include a complete blood count (CBC) with pathology review or a cytology/histology report of the bone marrow.

Lymph Node and Organ Aspirates:

1. Provide 4-5 cellular slides (either smears or cytospins) or fluid in an EDTA tube. Do not add extra fluid, such as saline or serum, to the sample. Glued cover-slipped slides are not usable for PARR.
2. Slides may be stained to confirm sample quality, and they can still be used for PARR testing.
3. Please include any relevant cytology or fluid analysis reports with your submission.

Cavity Fluid:

1. Submit cavity fluid in an EDTA tube and/or on 4-5 cellular slides (smears or cytospins).
2. If desired, stain the slides to confirm sample adequacy before submission.
3. Attach a copy of any cytology or fluid analysis reports.

Cerebrospinal Fluid (CSF):

1. Cytospin preparations (either stained or unstained) are ideal for CSF samples, but fluid in an EDTA tube is also acceptable.
2. To obtain a diagnostic sample, an estimated 50,000 lymphoid cells are needed. For instance, if the CSF has a lymphocyte concentration of 100 cells/µL, submit at least 500 µL or concentrate cells from 500 µL onto slides.
3. Include any cytology or fluid analysis reports.

Formalin-Fixed Paraffin-Embedded (FFPE) Tissue:

1. Paraffin embedded tissue block where Histopathology Laboratory will prepare the curls.
2. Provide five curls (or scrolls) from the histology block, each 20 µm thick, with curls intact as much as possible.
3. Attach either a histology report for the tested site or a concurrent histology request.

Collection Container

Tissue: Samples must be submitted in sealed, leak-proof, wide-mouth plastic containers. Glass containers are not acceptable and will incur an additional processing fee

Slides: Samples should be submitted in designated slide containers.

Turnaround time

14-21 days

Packing Instructions

Label each sample with the animal’s name and a unique identifier, using a permanent marker or a secure adhesive label. Ensure the submittal form is completed with the animal’s information and relevant medical history.

References

• Avery, A.C., & Burnett, R.C. “The Utility of PARR in Diagnosing Lymphoid Neoplasia in Dogs and Cats.” Veterinary Clinics of North America: Small Animal Practice, 2021.

• Keller, S.M., & Vernau, W. “Molecular Diagnostics in Veterinary Oncology: Applications of PARR Testing in Lymphoid Neoplasia.” Journal of Veterinary Diagnostic Investigation, 2022.

• Moore, P.F., et al. “Advances in PARR for Detecting Lymphoid Malignancies in Veterinary Patients.” Veterinary Pathology, 2023.