The use of amplified variable number of tandem repeats (VNTR) in the detection of chimerism following bone marrow transplantation - A comparison with restriction fragment length polymorphism (RFLP) by southern blotting

Chimerism analysis after allogeneic bone marrow transplantation (alloBMT) allows detection of early marrow engraftment, disease relapse, and graft rejection. Our objective was to do retrospective and prospective studies of chimerism analysis by restriction fragment length polymorphism (RFLP) by Southern blotting and variable number of tandem repeats (VNTR) by polymerase chain reaction (FCR) to compare and contrast the methods. The retrospective group comprised 46 samples from 26 patients previously analyzed by RFLP, while the prospective group contained 34 samples from 25 patients. Using four different VNTR primers (D1S80, D17S30, D1S111, and AFO-B), the recipient and donor samples amplified by the PCR were screened for unique banding patterns. The VNTR primer with the unique banding pattern was used to detect chimerism in each sample. A total of 635 VNTR analyses were performed. Interpretation was blinded for previous RFLP results. A comparison between the VNTR and RFLP results and a cost analysis of the two procedures were done. A unique VNTR banding pattern was present in 49 of 51 patients (identical twins in one case). The VNTR analysis showed complete chimerism in 68 samples, mixed chimerism in 9, and recurrences in 2. This agreed with the RFLP results in 64 (80%) of 80 samples. Failure to detect 1% to 10% of recipient DNA accounted for 15 (VNTR, 8; RFLP, 7) discordances. Follow-up revealed all donor DNA in five cases, decreasing quantities of recipient DNA in two cases (six samples), and no additional studies available in four cases. In one case, VNTR detected a complete chimerism when the DNA was insufficient for RFLP analysis. The cost analysis revealed an approximately 50% savings with the use of VNTR; VNTR is a viable alternative to RFLP in the detection of chimerism after bone marrow transplantation and offers substantial cost savings, faster turnaround time, easier preparation of the DNA, smaller DNA requirements, and the elimination of radioisotopes and cumbersome restriction enzymes.