BACKGROUND: Sequential monitoring of chimerism after hematopoietic stem cell transplantation is useful to document engraftment and predict graft failure or relapse. The introduction of highly sensitive methods such as in situ hybridization or PCR techniques allows the detection of mixed chimerism more frequently than do previous analyses using cytogenetics and Southern blotting. We studied the feasibility of a new commercial PCR assay with multiplex amplification of 16 short tandem repeat (STR) loci and fluorescent quantitation. METHODS: Serial post-transplant peripheral blood samples were collected from 22 patients follow-ing allogeneic bone marrow transplantations including eight AML, seven CML, two MDS transformed to AML, two NHL, and one case each of ALL, CLL, and SAA. DNA was amplified using a PowerPlex 16 kit and PCR products were quantified by an automated fluorescent DNA analyzer. RESULTS: There were 5-12 (average, 9.5) informative loci in the 16 patients who had received trans-plants from matched related donors compared to 11-14 (average, 12.2) informative loci in the six patients who had received unrelated donor transplants. Most patients achieved a complete donor chimerism (CC) rapidly around the day 30, which was sustained during follow-up. One patient each of AML, CML, MDS, and ALL who had CC at the first chimerism analysis showed an increase in recipient cells thereafter mostly preceding a morphological relapse. The CLL and one of the NHL patients never achieved CC and the most recent STR analysis showed persistent recipient cells. CONCLUSIONS: This method can provide a rapid, semi-quantitative assessment of chimerism in post-transplant patients. In cases lacking disease-specific markers, serial blood chimerism analysis offers an alternative for the potential early recognition of disease relapse when low levels of circulating neo-plastic cells are present.
Blotting, Southern ; Bone Marrow ; Chimerism* ; Cytogenetics ; DNA ; Follow-Up Studies ; Hematologic Neoplasms ; Hematopoietic Stem Cell Transplantation* ; Humans ; In Situ Hybridization ; Microsatellite Repeats* ; Multiplex Polymerase Chain Reaction* ; Polymerase Chain Reaction ; Recurrence ; Tissue Donors ; Transplants ; Unrelated Donors