Plasma or Serum: Which Is Preferable for Mutation Detection in Liquid Biopsy?

Area of Science:

• Oncology
• Molecular Biology
• Genetics

Background:

• Blood-based analysis of circulating tumor DNA (ctDNA) is crucial for cancer management.
• Plasma is the standard source for ctDNA, but large serum sample collections exist.
• Comparative studies of serum vs. plasma for ctDNA analysis are essential.

Purpose of the Study:

• To compare the utility of serum and plasma for detecting cell-free DNA (cfDNA) and ctDNA.
• To evaluate mutation detection efficiency and reproducibility in matched serum and plasma samples.
• To assess the suitability of serum and plasma for different liquid biopsy applications.

Main Methods:

• Analysis of cfDNA from matched EDTA-plasma and serum samples from healthy donors and cancer patients.
• Targeted next-generation sequencing using distinct gene panels.
• Comparison of mutation detection in serum, plasma, and matched tissue biopsies.

Main Results:

• Serum samples showed significantly higher total cfDNA and longer DNA fragments than plasma.
• Allele frequencies of spiked mutated nucleotides were approximately 50% lower in serum.
• Up to 44.8% of low allele frequency mutations were missed in serum, with lower concordance to tissue biopsies compared to plasma.

Conclusions:

• Serum cfDNA analysis is limited by dilution of ctDNA and reduced detection of low allele frequency mutations.
• Plasma is the preferred source for ctDNA in prospective liquid biopsy studies.
• Serum may have limitations for retrospective ctDNA analysis due to detection challenges.