Diagnostic Use
This assay uses short tandem repeat (STR)-based DNA profiling to determine the relative contributions of donor and recipient DNA in peripheral blood, bone marrow, or other suitable specimens following allogeneic haematopoietic stem cell transplantation (HSCT). Chimerism analysis is used to assess donor engraftment, monitor haematopoietic reconstitution, and assist in the detection of graft failure, mixed chimerism, or disease recurrence.
DNA profiling is performed using a validated panel of highly polymorphic STR markers. Informative loci that distinguish donor from recipient genotypes are identified, and the proportion of donor and recipient DNA is calculated for each informative marker. The overall percentage of donor and recipient chimerism is derived from the combined analysis of these markers.
Chimerism testing may be performed on unfractionated peripheral blood or bone marrow samples and, where clinically indicated, on cell lineage-enriched populations (for example, CD3+ T lymphocytes), which may provide greater sensitivity for detecting emerging mixed chimerism or relapse.
For patients undergoing a sex-matched allogeneic HSCT, DNA-based chimerism analysis is generally the preferred method for monitoring donor engraftment. Where serial chimerism monitoring is anticipated, a pre-transplant donor reference specimen should be retained for comparative analysis.
For sex-mismatched transplants, alternative methods such as sex chromosome fluorescence in situ hybridisation (FISH) may be considered.
Test Method
DNA profile analysis is performed using the Identifiler Plus Kit (supplied by Life Technologies NZ LTD / Thermofisher Scientific). Fragment analysis of PCR reactions from 16 loci by capillary electrophoresis on an Applied Biosystems Genetic Analyser is then performed by ChimerMarker software from SoftGenetics. This software compares each allele from all 16 loci and from the peak height of informative loci an average contribution of Donor or Recipient is calculated.
T cell selection is performed using the EasySepHLA Chim WB CD3 Positive Selection
Kit (supplied by STEMCELL Technologies).