Once ELISA kits are expired their performance can no longer be guaranteed. However, ELISA kits do not typically stop working entirely on their exact date of expiration and may continue to work for some time past the expiration. Again, although performance past the expiration date cannot be guaranteed, end users might still be able to obtain utilizable results. We recommend to validate the kit’s performance by running a stadard curve and a full set of recommended controls prior to potentially wasting precious samples. If the kit still shows good color development and all standard and control values are within reasonable paramenters, the kit may well be used past its expiration date.