For blood ctDNA tumor mutation detection, are there any kits with high extraction recovery rates that you would recommend?

Prioritize magnetic bead-based or silica column-based kits specifically designed for circulating cell-free DNA; do not make do with conventional genomic DNA extraction reagents. Check whether the instructions explicitly state recovery of cfDNA small fragments around 150-200 bp, and whether they have been validated with low-volume plasma. To assess recovery rate, do not rely solely on the concentration after extraction; it is recommended to purchase or borrow a cfDNA standard with a known fragment size, or run the extracted DNA on an AATI/Bioanalyzer to examine the fragment distribution. For 2-4 mL plasma, keep the elution volume as small as possible, for example 20-40 μL, to increase the final concentration. If a single column pass has low efficiency, the sample can be bound to the same column in two batches to avoid exceeding the column capacity.

Low concentration is not necessarily just an extraction kit issue—plasma separation is critical. For EDTA-anticoagulated blood, two-step centrifugation within 2-4 hours is optimal: first low-speed centrifugation to remove cells, then high-speed centrifugation to remove platelets and debris, avoiding hemolysis that releases genomic DNA; otherwise, the ctDNA proportion after extraction will be diluted, and qPCR Ct values will be falsely elevated. A plasma volume of 2-4 mL is already limited, so repeated freeze-thaw cycles are not recommended. If the volume is insufficient before extraction, low-volume preservation tubes can be used to reduce loss. Many domestic dedicated cfDNA extraction kits can achieve costs within 80 yuan, but after changing batches, parallel comparison with the original batch should be performed to assess Ct value shifts and the stability of weak-positive sample detection.

In terms of stock availability and budget, the per-test cost of imported classic cfDNA extraction kits usually exceeds your budget, and lead times may be 2–4 weeks; domestic professional magnetic bead-based or column-based kits are mostly in stock, with many shipping within 1 week, but you need to confirm whether they have medical device filing or are for research use only. It is recommended to first ask 2–3 suppliers to provide small samples or trial packs, aliquot the same batch of mixed plasma, perform parallel extraction, then run EGFR T790M qPCR, and compare Ct values, internal control uniformity, and total yield after extraction. If the budget is within 80 yuan, you can negotiate bulk packaging or research collaboration pricing; do not look only at the catalog price. At the same time, ask clearly about storage conditions, lysis binding time, and whether carrier RNA is included, as these affect recovery from low-concentration samples.