For ELISA detection of serum soluble PD-1 and PD-L1, which company's kit has stable sensitivity?

Channel and lead time: Within budget, domestic brands such as Huamei, Lianke, and Xinbosheng generally have stock or can deliver in 3-5 days; for imported R&D DuoSet, contact agents such as Dakewe and Uninv, and clarify the lead time and lot number. Testing 60 samples in duplicate wells requires at least two 96T kits, and it is recommended to order the same lot number at one time. Before ordering, ask the supplier to provide the COA, inter-batch CV, and applicable sample types, and preferably apply for 1-2 wells for trial use. Do not compare only prices, and avoid mixing different batches.

Large inter-batch variation largely depends on operation and sample handling. First, aliquot 60 serum samples into single-use portions to avoid repeated freeze-thaw cycles. Try to use kits from the same lot number and complete the measurement in one run; if batching is unavoidable, place 2-3 identical quality control samples across batches to check for deviations. Run standard curves in duplicate wells on each plate, and include low, medium, and high quality controls; if the QC CV exceeds 15-20%, retesting is recommended. Bring reagents to room temperature before reading, use a multichannel pipette for sample addition whenever possible, and ensure consistent plate washing. These measures are more effective at reducing inter-batch variation than simply switching brands.

In terms of brands, for stability prioritize R&D Systems' Quantikine or DuoSet. Quantikine kits offer low inter-batch variability when used as a complete set, but may approach or slightly exceed your budget; DuoSet antibody pairs are flexible and more suitable for large sample numbers, requiring self-coating, but with controllable inter-batch variability. Within budget, domestic options include Wuhan Huamei, Lianke Bio, and Xinbosheng. My experience is to buy one batch for trial testing first, don't stock up on two boxes right away. sPD-1 and sPD-L1 concentrations vary greatly between individuals; when selecting kits, ask for parallelism and recovery data in serum matrix.

For sensitivity, don't just rely on the range stated in the manual—redo the standard curve and lower limit of quantification yourself. For serum samples, it is recommended to test 2-3 dilutions for parallelism; if the concentration is not linear after dilution, it indicates matrix interference or nonspecific antibody binding. With R&D DuoSet, you can optimize the coating antibody concentration and blocking conditions to reduce background and improve low-value stability. For serum sPD-1 and sPD-L1, many patient samples are at low pg/mL levels, and low-value drift is a common source of inter-batch variation. It is recommended to add additional standard points near the lower limit of quantification.