High Inter-Assay CV from Inconsistent Sample Storage (ELISA (Inconsistent Results / High CV))

Question

Accepted Answer

High inter-assay coefficient of variation (>15%) when the same samples are tested across different runs. Sample readings decrease over time or vary unpredictably between runs. Common causes: 1) Samples stored at inconsistent temperatures between runs 2) Unequal number of freeze-thaw cycles across different samples 3) Sample preparation methods vary between runs (dilution, mixing, timing) 4) Samples not stored according to manufacturer recommendations (temperature, additives) 5) Degradation of analyte in samples due to improper storage conditions Solutions: 1) Ensure all samples are stored and prepared consistently according to kit recommendations 2) Keep the number of freeze-thaw cycles equal across all samples; aliquot samples to avoid repeated thawing 3) Document and follow standardized sample preparation protocols for all runs 4) Store samples at recommended temperature (typically -20°C or -80°C for long-term storage) 5) Add protease inhibitors or stabilizers if recommended by the protocol