From Wendy Sutula, Hi, George. We are validating a new vendor's ACA
kit. When we perfom patient ACA
tests, the serum samples are frozen at
–20 for 2–7 days before tesing. When
establishing or validating the reference range for the new vendor's kit, is it acceptable to use serums which have been collected and frozen within two hours of collection at –70 instead of –20, and for periods of time longer than 1 week, or must we adhere to the same storage requirements prior to testing as for the patient samples? I couldn't find a specific reference to address this in the CLSI documents. Thanks so much.
Hello, Wendy, and thank you for your question. As you confirm, except for shelf life, there is no CLSI guideline or standard that specifically addresses variant frozen storage temperatures, although in we are required in general to match calibrator, control, proficiency testing, and patient specimen management. In the absence of a specific guideline, I feel comfortable offering an opinion based on experience. ACA assays offer only mediocre precision, and are semiquantitative. Consequently, modest specimen management differences seem tolerable. Further, on the day of an ACA run, most facilites are likely to run freshly centrifuged patient specimens collected that day alongside thawed specimens. This seems like an acceptable practice with no negative consequences.
Meanwhile, just out of curiosity, are you not in a position to store your patient specimens at –70?