New dynamics in monitoring diagnostics in leukemia
Dresden, 14. March 2017. Diagnosis leukemia and stem cell transplantation
The diagnosis "leukemia" for patients means to undergo several stressful therapeutic interventions. If chemotherapy is not effective, stem cell transplantation mostly is the last chance for healing. However, a sudden graft rejection or disease relapse can always occur despite the successful transfer of the hematopoietic stem cells from donor to recipient. Therefore, the regular quantitative assessment of the donor and recipient cell-portion in the blood or bone marrow of the patient - the chimerism analysis - plays a pivotal role in routine diagnostics.
Digital droplet PCR (ddPCR)
A variety of sensitive PCR techniques are commonly used to determine genetic chimerism within routine diagnostics. With the new "digital" droplet PCR generation (ddPCR), a forward-looking technology has now been added. It makes the absolute quantification of the "target DNA" faster and more sensitive. The principle of ddPCR is based on the distribution of the reaction mix with the included target DNA into thousands of small droplets. Fractions of droplets may thus contain the template or not. Each single droplet represents a closed reaction chamber for the DNA amplification. Due to the labeling of the target DNA with fluorescent dyes, droplets can be counted by containing the target-DNA or lacking the target DNA and can be divided into so-called droplet clusters. By these special features very small amounts of DNA can be specifically and quantitatively detected.
Chimerism analysis performed in “digital“ droplets
Biotype Diagnostic GmbH is the first company that incorporates this innovative technology into its chimerism portfolio. In addition to the already available diagnostic methods Mentype® Chimera and Mentype® DIPscreen / DIPquant, the new assays Mentype® DigitalScreen and Mentype® DigitalQuant allow the determination of the chimerism status by using the digital droplet PCR. Donor and recipient DNA are first examined for 29 DNA markers (insertions / deletions) in order to identify distinctive features, so-called informative DNA loci. These informative loci can then specifically be addressed with the multiplex test systems Digital Quant´s to monitor post stem cell transplantation samples. In contrast to other quantitative PCR methods, ddPCR allows an absolute quantification of target DNA. Hence, the absolute quantification of the chimerism status can be carried out with less effort and, therefore, is more cost-effectively. In addition, this new assays enable a highly sensitive and statistically robust data analysis over a broad measurement range. Especially in chimerism samples that prove difficult to be analyzed with conventional quantitative PCR methods, the new ddPCR assays show their advantages. This means for the treating physician to recognize an imminent disease relapse more securely and earlier than before.
