# When are patients' blood samples stored long-term?

**URL:** <https://boards.straightdope.com/t/when-are-patients-blood-samples-stored-long-term/931277>\
**Category:** Factual Questions\
**Created:** [January 23, 2021, 11:24am UTC](https://boards.straightdope.com/t/when-are-patients-blood-samples-stored-long-term/931277 "2021-01-23T11:24:12Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![Chad\_Sudan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chad_sudan/32/4509_2.png) [@Chad\_Sudan](https://boards.straightdope.com/u/Chad_Sudan)\
**Post date:** [January 23, 2021, 11:24am UTC](https://boards.straightdope.com/t/when-are-patients-blood-samples-stored-long-term/931277/1 "2021-01-23T11:24:13Z")

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Sometimes a patient’s illness is misdiagnosed or goes undiagnosed.

This is especially the case when the illness is a new one, as in the early days of AIDS or COVID-19.

Once a new illness emerges, tracing a Patient Zero becomes a high priority – but in the meantime, the earliest patients have often died, and no blood samples remain.

Under what circumstances would a patient’s blood sample be retained long-term so that it could be tested later? And how long would such samples be stored? I imagine it’s not practical to retain such samples without a compelling reason.

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**Author:** ![puzzlegal](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/puzzlegal/32/3827_2.png) [@puzzlegal](https://boards.straightdope.com/u/puzzlegal)\
**Post date:** [January 23, 2021, 11:32am UTC](https://boards.straightdope.com/t/when-are-patients-blood-samples-stored-long-term/931277/2 "2021-01-23T11:32:49Z")

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I don’t know what the rules are now, but i worked as a lab assistant in the 80s and we had a -70 chest freezer full of old plasma samples from people who had had blood tests. As part of some research project i had to fish out a couple dozen of them (they were identified by number) defrost, remove enough to test for something, and return the rest of the sample to the freezer.

I may not have understood what was going on there, but i believed that everyone who’d had blood tests done by that department had the leftover stored in that freezer.

It was in the endocrinology department of a research hospital.

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**Author:** ![gdave](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/gdave/32/3683_2.png) [@gdave](https://boards.straightdope.com/u/gdave)\
**Post date:** [January 23, 2021, 1:52pm UTC](https://boards.straightdope.com/t/when-are-patients-blood-samples-stored-long-term/931277/3 "2021-01-23T13:52:42Z")

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I work for a major private diagnostic lab, but in logistics, _not_ in actual laboratory operations, so I’m not 100% sure on this, but I think my company keeps blood specimens 3-7 days after testing, depending on the type of specimen and the type of tests. It’s just not practical to keep them indefinitely. It takes a _lot_ of room and energy and costs significant money when you’re talking about processing thousands of specimens a day.

Also, important to note, most blood tests have to be performed within a 24-72 hour window. Many have to be performed within a few hours (“STAT” tests). Preserving blood samples beyond those windows doesn’t actually serve any purpose.

On the other hand, many _tissue_ specimens are _much_ more stable. Our pathology lab stores tissue blocks preserved in paraffin for _years_ after the initial testing, and I’ve transported tissue blocks between our lab and other medical facilities that were a year or more old. I’ve seen online references that properly prepared and stored paraffin blocks are stable for _decades_. I don’t think they’d be particularly useful for retroactive diagnosis of an infectious disease, though.