What does "immediately" mean?

My thoughts on this one to define immediately within the room temperature stability time. If the analyte stability statements include 'must be refrigerated (or frozen) within 15 minutes', then your immediately is within 15 minutes.

This would be very dependent on the test and the test system:

I have a test system that stipulates to test "immediately" after draw and I can tell you that translates to within 1 minute, preferably less.  A whole blood sample drawn without additives for a POC coagulation test ran 15 minutes after draw wouldn't provide valid results.  

Just to clarify - you are having whole blood samples collected without anticoagulant/preservative in your ED, but delivering to lab for lab staff to perform on POC-type devices?  Or did I misunderstand.

No, the nursing staff is collecting vacutainers, so this would be green top lithium heparin tubes, mostly for lactate and blood gas for ChemSTAT and i-STAT. Also, the Clinitek urine pregnancy states "test immediately".

I see.  Yes, that's certainly something you won't get much help from vendors on, since the intention is to perform it bedside.  Without a study to validate the time window for which you'll consider the sample to be acceptable after collection, I don't know another way of locally validating what "immediately" is.  I could see some regulatory folks interpeting this as off-label use even with a study.  Definitely a question for your accreditor.

Interesting question considering an issue I've seen recently in my EDs.  Historically, they have always collected iSTAT troponin in a green top.  Well, they hate the dispensers we use (I do too) and I've recently found out that they have moved away from the green top to pulling from an IV start into a plain syringe, straight into the cartridge.  The IFU for Trop and the iSTAT manual state that if pulled into plain syringe, it should be tested immediately (under 1 min is stated in the manual).  The move from green top to syringe has also seen an increase in false positive Trops that I now believe to be a result of micro clots (also stated as a possibility in the manual).  So that tells me that "immediately" is not working and they must not be testing in under 1 min.  I am now on the search for
a POC blood dispenser that works and doesn't break us financially, haha. Mary

Interesting, Mary.  I thought that Abbott had banned use of non-anticoagulated samples for everything but coagulation tests, but as you said, they allow it as long as done "immediately."  They only insist on heparinized samples for the blue CG4+ cartridges.  Because that, of course, makes sense (insert sarcasm here)...