Personalized chimerism test: selection of short tandem repeat or quantitative PCR depending on patient’s chimerism status

Publication date: Available online 20 February 2019Source: The Journal of Molecular DiagnosticsAuthor(s): Jennifer Tyler, Lorie Kumer, Carolyn Fisher, Heather Casey, Hiroko ShikeAbstractChimerism testing is used to monitor engraftment and risk of relapse after allogeneic hematopoietic stem cell transplant for hematological malignancy. Although short tandem repeat (STR) method is widely used among clinical laboratories, quantitative PCR (qPCR) provides better sensitivity (0.1%) than STR (1% to 5%), but is less accurate than STR for patients in mixed chimerism. qPCR chimerism test allows evaluation of residual recipient cells as a surrogate of measurable residual disease. To achieve higher sensitivity and accuracy, we applied qPCR or STR, based on patient chimerism status (recipient alleles <5% or ≥5%, respectively). Of the 230 patients tested by STR chimerism in a one year period, excluding 10 deceased patients, 30 qPCR markers were genotyped and 167 patients converted to qPCR chimerism (76%), including eight patients with multiple donor transplant. STR was continued on 53 patients (24%) for the following reasons: mixed chimerism, lack of donor/pre-transplant DNA, and insufficient qPCR informative markers. Insufficient qPCR markers were seen in patients with related donors only (8/60 patients, 13.3%). qPCR detected residual recipient chimerism in 85.5% of patients assigned “complete chimerism” by STR (<5% recipient). Selecting STR or qPCR based on each patient’...
Source: The Journal of Molecular Diagnostics - Category: Pathology Source Type: research