Test ID: CHIMS    
Chimerism Transplant Sorted Cells, Varies

Genomic DNA is extracted from blood or bone marrow aspirate samples using an automated extraction machine (EZ1 BioRobot, Qiagen) and used in a commercial kit GlobalFiler PCR Amplification KIT (Applied Biosystems, Foster City, CA) following the manufacturer's instructions. Briefly, 20 different short tandem repeat (STR) marker regions are amplified in single multiplex PCR using primers labeled with fluorescent tags. The products are analyzed for size and amount using capillary electrophoresis on an ABI3500xl genetic analyzer. For the initial sample on any patient, the test is performed on 3 separate DNA samples: donor germline DNA, recipient germline DNA, and recipient post-transplant sample for chimerism determination. The STR profile of the germline samples is used to identify markers that can distinguish between the donor and recipient. Based on these profiles, the percentage of donor and recipient DNA is then determined in the post-transplant sample using the assumptions and calculations outlined in Thiede et al. Subsequent samples for chimerism evaluation do not need to be accompanied by samples for donor and recipient germline evaluation, as the profiles from the initial testing are kept on file for comparison.(Instruction manual: EZ1BioRobot System. July 2005. Qiagen. www.qiagen.com; package insert: GlobalFiler PCR Amplification Kit. User Guide. Applied Biosystems, Foster City, CA, www.appliedbiosystems.com; Thiede C, Florek M, Bornhauser M, et al: Rapid quantification of mixed chimerism using multiplex amplification of short tandem repeat markers and fluorescence detection. Bone Marrow Transplant 1999;23:1055-1060)

The sensitivity of this analysis is approximately 5% in a posttransplant specimen (donor and recipient DNA mixed chimerism).

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