Recommendations for human serum TNF-α ELISA kits: How to choose when the sample volume is small?

TNF-α levels in sepsis serum vary greatly between individuals, so it is not recommended to measure undiluted samples directly, as they can easily exceed the upper limit or be affected by matrix interference. First take 2-3 representative samples and test at 1:2, 1:5, and 1:10 dilutions to see which dilution falls in the middle range of the standard curve, then run the batch. After dilution, a 60 μL sample takes up less volume and puts less pressure on duplicate wells. The standard curve usually occupies 16 wells (blank + standard curve). The remaining 80 wells can test 40 samples in duplicate or 80 samples in singlicate. Since your sample size is small, it is recommended to include 2 high-value quality controls alongside the standard curve, screen samples in singlicate first, and retest abnormal samples, which is more reliable than forcing all samples to be run in duplicate.

Dealers with local warehouses in Shanghai generally have more reliable lead times. It is advisable to inquire simultaneously with Dakowei Shanghai, UNIV Shanghai, Lianke East China agent, and Xinbosheng Shanghai office, etc., and request confirmation of stock availability, shipping time, and invoicing. Domestic kits are generally faster than imported ones in terms of stock availability and are easier to match within budget; imported R&D and Thermo small-specification products have limited stock and may exceed budget. Regardless of whether domestic or imported, before placing an order, ask the sales representative to send the instruction manual or electronic version, and focus on verifying sample volume, applicable sample type (serum), incubation time, and whether low sample volume is supported. Your samples are precious, so don't just prioritize speed—run a dilution pilot experiment first.

If you truly cannot find a kit with a sample volume below 25 μL, there is no need to force duplicate wells, as this can easily cause falsely low values due to pipette tip dead volume. You may consider diluting the serum 1:2 and loading 50 μL/well, but the kit sensitivity must be sufficient to compensate; alternatively, switch to a chemiluminescence/electrochemiluminescence platform with a sample volume of 10-25 μL, though the budget will be higher. A more practical approach: first use existing samples to screen a kit, perform dilution linearity and lower limit of quantification testing on 2-3 septic serum samples, and if the concentration after dilution remains above the lower limit of quantification, adopt diluted single-well testing plus duplicate-well verification for some samples, rather than blindly pursuing duplicate wells for all.

With a sample volume of only 60 μL and the need for duplicate wells, it is recommended to prioritize kits with a sample volume of ≤25 μL per well; otherwise, the combined dead volume of the two duplicate wells plus the pipette tip will be insufficient. When selecting a kit, focus on the sample volume and sensitivity (LOD) in the instructions. For sepsis samples, it is advisable to choose models with an LOD around 1-5 pg/mL and an upper detection limit above 1000 pg/mL. Within a budget of 3,000, domestic options offer more choices, such as the TNF-α series from Lianke, Xinbosheng, and Dakewe. For delivery to Shanghai within two days, you can first inquire with Shanghai Xitang, Uninvire, or Dakewe's Shanghai office, confirm the in-stock lot number before placing an order, and request a COA to verify dilution linearity.