PF771 CHIMERISM MONITORING BY QPCR, A ROBUST PERFORMANCE FROM 0.05% TO 100%

Abstract

Background:Investigating the chimeric status after stem cell transplantation is required for the detection of adverse transplant events. In comparison to STR analysis, qPCR allows for a quick and easy measurement with better sensitivity that can be as low as 0.05% for the recipient chimeric status. In comparison to STR analysis this is a substantial improvement.Aims:The presumption is that qPCR is most accurate in its detection of percentages below 20–30% and less accurate for higher percentages. Here however, we provide evidence that qPCR data can be trusted regardless the level of measured percentage.Methods:We have collected the data of 19 studies, spanning 6 years, from the UK NEQAS ‘Post‐Stem Cell Transplant Chimerism Monitoring’ trial. Each study consisted of four samples; one from the recipient, one from the donor and two samples with a chimeric status representing two time points after transplantation. The recipient and donor samples were genotyped applying the KMRtype workflow (GenDx) and the chimeric mixtures were then examined with all found informative assays applying the KMRtrack workflow (GenDx). Tests were performed on either a Viia7 or QuantStudio 6 qPCR system (Thermo Fisher).Collected data was compared with the results reported by UK NEQAS, which are based on the results from all participating labs. From this comparison the standard deviation and relative error of the qPCR assay were calculated and plotted in an overview.Results:The chimerism percentages obtained covered a full range of chimeric status from 0 to 100%. When comparing the qPCR data with the data provided by UK NEQAS it indeed shows a higher absolute deviation with higher percentages in the qPCR data. However, in the qPCR data the relative error is the same throughout the whole range of chimeric status.Summary/Conclusion:From these results we can conclude that the qPCR technique is able to accurately detect genetic material in a chimeric mixture, not only in the lower levels but confidently from 0.05% to 100%.