Development and performance of a next generation sequencing (NGS) assay for monitoring of mixed chimerism

The aim of this study was to evaluate the performance of a novel NGS-based assay to monitor mixed chimerism (MC) and compare its technical capacity to established techniques for chimerism analysis. Artificial and clinical samples with increasing amounts of patient DNA were compared using real-time PCR detection of indels and SNP, fragment analysis of short-tandem repeats (STR) and NGS analysis of indels. Real-time PCR displayed excellent sensitivity (>0,01%) but poor accuracy (>20 CV% at MC > 20%), while fragment analysis exhibited good accuracy (<5 CV% at MC > 20%) with limited sensitivity (>2,5%). In contrast, NGS chimerism demonstrated a sensitivity (>0,1%) equal to real-time PCR and an accuracy equal or better than STR analysis throughout an extensive range of mixed chimerism (0,1 - 100%). To evaluate performance of the separate techniques for chimerism determination, 75 retrospective patient monitoring samples (3-7 weeks post-HSCT) with low (<5%), intermediate (5-20%) or high mixed chimerism (>20%) were analyzed. The between run precision for the NGS assay varied from 0,72% (>20% MC) to 7,38% (MC < 5%). In conclusion, NGS displayed a combination of high sensitivity with good accuracy in both artificial and clinical chimerism samples.