Characteristics of a chimerism NGS assay with unmatched sensitivity

Improving chimerism measurement in post-transplant patient monitoring 
Relapse of the underlying malignant disease is a major complication after hematopoietic stem cell transplantation (HSCT). Clinicians need reliable and sensitive methods to detect relapse as early as possible and trust the results of the test used. Different methods to determine chimerism have been developed and are currently used in laboratories worldwide. Here we present the characteristics and performance of Devyser Chimerism, an NGS-based chimerism method with unmatched sensitivity. 

Population-independent highly informative genetic markers 
The Devyser Chimerism NGS kit for the detection of mixed chimerism employs highly informative genetic markers distributed through the human genome. The markers have been selected to be population-independent (figure 1). The kit enables screening of donors and recipients prior to HSCT, as well as quantitative determination of mixed chimerism in the recipient following HSCT. 

Informative markers 
When testing screened patients, Devyser Chimerism exhibited at least three (average eight) and at least two (average five) informative genetic markers (indels), suitable for monitoring mixed chimerism of patients with their corresponding matched unrelated or related donor samples (Fig. 2) 

Figure 2 Number of informative markers in related HLA matched pairs and unrelated HLA matched pairs (MUD)  

A sensitive and precise assay  
When comparing Devyser Chimerism to other methods, real-time PCR although very sensitive, has poor precision above 20% chimerism.  In comparison, fragment analysis exhibits good precision, but with limited sensitivity (>   2,5%). In contrast, Devyser Chimerism demonstrates very good sensitivity, with a limit of detection (LOD) of 0.1% chimerism, and precision throughout the whole spectrum of patient/donor mixed chimerism (figure 3). 

Figure 3. Devyser Chimerism compared to STR and Real-time PCR analysis (low level). STR analysis failed at 1 and 0,5% 

Conclusion 
The results of our studies showed that the Devyser Chimerism assay is suitable for monitoring patient/donor chimerism after allogeneic hematopoietic stem cell transplantation (HSCT), with high sensitivity (LOD 0,1 %) and a broad dynamic range (detection range 0,1-100%)  with good precision and accuracy throughout the whole spectrum of chimerism  (% patient/donor)  

Devyser Chimerism employs non-population dependent, highly informative genetic markers which provide stable resolution power. By utilizing the CE-IVD Devyser Chimerism kit, early rejection detection with trusted results is made possible. 

Sources 

1.  Chimerism analysis for clinicians: a review of the literature and worldwide practices (Chimerism analysis for clinicians: a review of the literature and worldwide practices - PubMed (nih.gov))  
2. A practical guide to chimerism analysis: Review of the literature and testing practices worldwide - PubMed (nih.gov)  
3. Development and performance of a next generation sequencing (NGS) assay for monitoring of mixed chimerism - PubMed (nih.gov)  
4.  Early relapse prediction after allogeneic hematopoietic stem cell transplantation for acute lymphoblastic leukemia (ALL) using lineage-specific chimerism analysis - PubMed (nih.gov)  
5.  Evaluation of Next-Generation Sequencing and Crystal Digital PCR for Chimerism Monitoring of Post-Allogeneic Hematopoietic Stem Cell Transplantation - PubMed (nih.gov)