Practical informativeness of short tandem repeat loci for chimerism analysis in hematopoietic stem cell transplantation

Objective Short tandem repeat (STR) loci are most frequently used for chimerism analysis after hematopoietic stem cell transplantation (HSCT). The aim of this study was to evaluate the practical informativeness of STR chimerism by integrating theoretical and analytical points. Methods Theoretical and practical informativess of 16 STR loci were evaluated from 1249 pairs of recipients and donors who were prepared for HSCT. Results Theoretical informativeness was influenced by genetic diversity including allele frequency and heterozygosity, and was higher in the unrelated HSCT group (90.5 ± 5.3%) compared to the related HSCT group (66.2 ± 4.4%). Practical informativeness was lower than theoretical (6.1 ± 1.7%) because several STR loci were excluded due to stutter peaks and less reliable results, especially in type II-2 donor-recipient match pattern with no recipient-specific allele. We simulated an efficient STR combination for reliable chimerism analysis. Eight informative STR loci were required to analyze chimerism with at least one practically informative locus in the related HSCT group (D18S51, FGA, D2S1338, D13S317, D8S1179, D21S11, D16S539 and D7S820) while only three loci were needed in the unrelated group (D2S1338, FGA and D18S51). A minimum set of 2, 4 or 7 STR loci were required to provide at least 1, 3 or 5 practically informative loci in 95% of the unrelated HSCT group while 3, 8 or 12 loci were required in the related HSCT group. Conclusion We deducted the practical informativeness of STR chimerism, identified the major influencing factors on the practical informativeness of each STR locus, and successfully simulated the efficient STR combination for reliable chimerism analysis.