General discussion and future perspectives 181 8 specificity of methylation analysis in self- as compared to clinician-collected screening samples. To optimise methylation-based triage using self-collected samples, there are several steps within the workflow that may be subject to improvement (Figure 8.3). 1. The choice of the self-sampling device is crucial in optimising the collection process. Various self-collection devices are on the market, and each may differ in its collection properties and DNA yield 97, which may impact clinical performance of subsequent assays; 2. Preservation of self-collected samples prior to laboratory testing. Instead of dry storage and transport, a storage medium will aid in stabilising nucleic acids, providing protection against potential degradation; 3. An alternative sample resuspension medium designed to facilitate downstream sample processing for molecular analysis with enhanced DNA recovery and better DNA quality for methylation analysis; 4. A larger fraction of the self-collected sample may be used in DNA extraction and subsequent analysis. Target enrichment can be achieved by reducing the concentration of non-target DNA and/or increasing the concentration of target DNA. Rodems et al. 98 described an semi-automated method for enrichment of methylated DNA from low-input samples, called SEEMLIS; 5. Alternatives to bisulphite conversion of isolated DNA, such as direct cell conversion (Chapter 5), enzyme-based conversion or methyl-specific restriction enzymes, can be employed; 6. Technical advancements in DNA methylation analysis can be achieved by, for example, Oxford Nanopore sequencing or redesigning the qPCR. Potential strategies to consider for the latter are exploring other amplification enzymes, redesigning the current primer/probe sets 99, increasing the input of bisulphite-converted DNA, or boosting the amplification signal by detecting multiple PCR targets in the same detection channel. Altogether, advancements in each step may contribute to the development of more sensitive and specific detection of methylated DNA in low-input samples, such as selfcollected (cervico-) vaginal specimens and urine. 8.2.3 OTHER SELF-COLLECTION METHODS TO INCREASE SCREENING COVERAGE Despite the introduction of cervicovaginal self-sampling in cervical cancer screening programs, still a significant number of women do not participate, amongst others women
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