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BACKGROUND: Clinical decision making after allogeneic stem cell transplantation (HSCT) is partially based on hematopoietic chimerism analysis. Polymerase chain reaction amplification of polymorphic short tandem repeats (STR-PCR) is currently considered the gold standard for chimerism surveillance after transplantation. Nevertheless, this method has shown several limitations. Emerging technologies such as digital PCR (dPCR) has been applied to detect hematopoietic chimerism. Despite previous reports, the clinical usefulness of dPCR is unclear because the studies were performed in limited patient populations with short follow-ups. METHODS: In order to compare hematopoietic chimerism detection time and rate, we analyzed 591 samples from 155 patients undergoing gender-mismatched HSCT using STR-PCR and dPCR. We also established the correlation between both methods in artificial DNA mixtures prepared in known proportions and in clinical samples. RESULTS: Depending on the artificial DNA mixture analyzed the correlation coefficient between both methods was 0.9946 and 0.9732. The limit of detection for dPCR was 0.01%. Of 157 samples with donor and recipient DNA, mixed chimerism (MC) was detected solely by dPCR in 66 samples. Within the group of patients relapsing after HSCT (n=32) MC was detected earlier in 15 of these patients with dPCR in comparison with STR-PCR. The mean time from MC detection to relapse was 155 days (range: 13-385 days) and 65 days (range: 0-203 days) for dPCR and STR-PCR, respectively. CONCLUSIONS: dPCR is a sensitive and accurate method for the quantification of hematopoietic chimerism allowing earlier MC detection compared to STR-PCR.
Waterhouse et al. (Wed,) studied this question.