Indel analysis by droplet digital PCR: a sensitive method for DNA mixture detection and chimerism analysis

Area of Science:

• Molecular Biology
• Genetics
• Forensic Science

Background:

• Chimerism analysis is crucial for monitoring outcomes after allogeneic hematopoietic stem cell transplantation (HSCT).
• Existing methods for detecting mixed chimerism may lack the sensitivity required for early or low-level detection.
• Droplet digital PCR (ddPCR) offers potential for high-sensitivity nucleic acid quantification.

Purpose of the Study:

• To evaluate the effectiveness of ddPCR for mixed chimerism detection in HSCT patients.
• To compare the performance of ddPCR with established Indel and Short Tandem Repeat (STR) analysis methods.
• To assess the sensitivity of ddPCR in detecting low-level DNA contributors in mixed samples.

Main Methods:

• Analysis of 25 DNA samples from HSCT patients using ddPCR, Indel analysis, and STR analysis.
• Creation of eight artificial DNA mixture samples to test ddPCR sensitivity.
• Statistical comparison of chimerism percentages obtained from different methods.

Main Results:

• ddPCR analysis of a single Indel showed high correlation with 15 STRs (r² = 0.970) and 38 Indels (r² = 0.975).
• ddPCR detected a minor DNA contributor down to 0.5% in artificial mixture samples.
• Results indicate ddPCR's high sensitivity and accuracy in mixed chimerism assessment.

Conclusions:

• ddPCR is a powerful and sensitive tool for clinical chimerism analysis post-HSCT.
• ddPCR surpasses traditional methods in detecting low-level mixed chimerism.
• This technique is valuable for forensic mixture analysis and clinical applications requiring high sensitivity.