Sensitivity of chimerism is dependent on the method applied, ranging from only 10−2–10−3 in the conventional method using fragment analysis of short tandem repeats (STR) or in XY-FISH analysis method in sex-mismatched donor/recipient, to a high sensitivity of 10−4–10−5 if variant-allele-specific quantitative PCR that can detect small DNA insertions or deletion or evaluation of CD34+ cell subset in AML were used (48–50). The gene discussed is CD34; the disease is acute myeloid leukemia.