The Precursor Cell Marker test, commonly called the CD34 panel test, determines the level of CD34 marker in your blood. The test can be prescribed to check your viability as a bone marrow donor. The CD34 is an important antigen that features heavily during bone marrow transformations. Usually, the CD34 panel test is done in combination with other tests to confirm whether your Human Leukocyte Antigens (HLAs) markers are a good match with that of the recipient. The HLAs are proteins, or markers, found on most cells in the human body. Through these markers, the immune system can recognise which cells belong to your body and which do not. In the end, if the donor’s HLA is similar to the recipient’s, the latter’s immune system will not reject the bone marrow.