Advanced Concepts

Occasionally, specimens may be received in the laboratory after engraftment without pre-engraftment information. In this case, the blood or bone marrow of the recipient is not acceptable for determination of recipient-specific alleles because the alleles present are likely to represent both donor and recipient. The specimen can be processed using the amelogenin locus or Y-STR markers if the donor and recipient are of different sexes, preferably female donor and male recipient. Another option is to use an alternate source of recipient DNA such as buccal cells, skin biopsy sample, or stored specimens or DNA from previous testing. Because of the nature of lymphocyte migration, however, skin and buccal cells may also have donor alleles due to the presence of donor lymphocytes in these tissues. The best approach is to ensure informative analysis of the donor and recipient as part of the pretransplant schedule.

reduced-intensity pretransplant protocols, testing is recommended at 1, 3, 6, and 12 months. Because early patterns of engraftment may predict GVHD or graft failure after nonmyeloblative treatments, even more frequent blood testing may be necessary, such as 1, 2, and 3 months after transplant. Bone marrow specimens can most conveniently be taken at the time of bone marrow biopsy following the transplant, with blood specimens taken in intervening periods. Usually, 3-5 mL of bone marrow or 5 mL of blood is more than sufficient for analysis; however, specimens collected soon after the transplant may be hypocellular so that larger volumes (5-7 mL bone marrow, 10 mL blood) may be required.

Quantification of percent recipient and donor post-transplant is performed using the informative locus or loci selected during the pretransplant informative analysis. The raw data for these calculations are the areas under the peaks generated by the PCR products after amplification. The emission from the fluorescent dyes attached to the primers and thus to the ends of the PCR products is collected as each product migrates past the detector. The fluorescent signal is converted into fluorescence units by the

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