Chimerocyte panel detects low target copies in high background levels (highly sensitive), does not amplify background (highly specific), and correlates with measurements from a gold standard method. (A) Two, 2, and 6 replicates, respectively, of 16, 4, and 1 target gEq were run with 3 different nontarget (background) levels amplifying at an acceptable cycle at a threshold ranging from 31.4 to 44.6. The amplifications were comparable per the background level and self-consistent per the individual assay. The 1 gEq dilution sometimes yielded no amplification (threshold, NR); this is statistically expected when pipetting such low target copy numbers. When targets were absent (nontemplate controls) the background was never amplified. (B) Comparison of recipient chimerism quantification using ultrasensitive chimerism (Chimerocyte) technique vs standard-of-care STR technique conducted using the gDNA from BMAs and PB-derived cells of patients with leukemia. Below a proportion of 0.01, chimerism was not detected (Not-Det) using STR. Error bars are 95% CIs of the measurements. Agreement between the methods was high and extreme outliers (ie, >0.1 in 1 assay vs Not-Det in the other) remained sparse and often with reduced accuracy (ie, large 95% CIs). Not-Det, not detected; NR, not reached; NA, missing or not available.