What is a key consideration when interpreting PCR results in engraftment tests?

In the context of PCR results for engraftment tests, the key consideration is that only donor DNA should be present after a successful engraftment. The primary purpose of these tests is to determine whether the transplanted cells (the donor cells) have established themselves and are proliferating in the recipient.

The presence of only donor DNA indicates effective engraftment; it suggests that the donor cells have taken over in the hematopoietic (blood-forming) system of the recipient. If recipient DNA is detected in significant amounts, it may imply that the donor cells have not sufficiently engrafted or that there has been a failure of the transplant, as it shows that the native population of the recipient's cells is still predominant.

While the presence of unknown alleles could be seen in various contexts, in a successful engraftment scenario, the goal is to detect the specific alleles of the donor rather than any non-contributory or unknown alleles. The focus is on ensuring that the transplant has effectively established itself, which is demonstrated through the exclusive presence of donor DNA.