Chimerim analysis using STR (short tandem repeat)multiplex polymerase chain reaction. Genomic DNA, extracted from mononuclear, polynuclear, or PBSC CD34⁺ cells, was used as a template for amplification of 16 polymorphic STR markers (AmpFlSTR Profiler Plus Kit; Applied Biosystems). Full donor chimerism was detected in all informative STR markers (9 of 16) at time of relapse (January 2010), after salvage chemothery in both PBSC CD34⁺ collections (July and August 2010) and 1 month after PBSC infusion (October 2010). Three representative STR markers (D2S1338, FGA, and D21S11) were depicted.