Serum or plasma should be prepared from a whole blood speclmen obtained by approved aseptic technique. If testing cannot be done within an hour after sample collection, refrigerate the specimen (maximum 2 day at 2-8°C) and let it retire to room temperature before testing. If prolong storage is required, samples should be stored at -20°C Avoid freeze-thaw of specimen during storage. Sample suspected to microbial contamination should not be used.