exlimey

An excellent question. In theory, there is no such thing as "too cold" for a freezer, so the low temp. alarm setting seems to be pointless. However, if such a unit does activate a low temp. alarm, it may indicate that the unit is malfunctioning in some way. It might just give you time to intervene before the unit goes "bang". I hope I've sufficiently emphasized the low probabilities of the above happening. Our facility still checks the low alarm points for our walk-in freezers (-20 C). Luckily, we have access to liquid nitrogen (LN2) which is very convenient and quick. In the past, we've very awkwardly used a sludge of alcohol and dry-ice to get a very low temperature (-60 C), but this doesn't help with ultra-colds (-80 C). For physical science reasons, we are unable to activate the low alarm on our liquid nitrogen tank !!!! We actually had an inspector challenge us on this issue a number of years ago.

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The Rh typing reagents are designed to react that way. These days, the reagents are monoclonal, IgM in nature and give direct agglutination in a very short amount of time (similar to anti-A and other ABO reagents). Centrifugation is also usually part of the process. Antibodies to Rh antigens in patients (or donors) are typically IgG and require incubation and an antiglobulin phase. Most manual tube testing systems these days also use a potentiator to enhance reactivity and/or reduce incubation times. In the "bad-old-days", Rh typing reagents were human-source, IgG in nature and usually required incubation and an antiglobulin phase.

I like that ! None of this wishy-washy, barely reactive stuff.

I agree with Malcolm. In theory, there may be examples of anti-K that only react with K+k- cells, but in practice it's a very rare event. One of my former colleagues/mentors once said that one shouldn't worry about missing a weak antibody. If the patient were unfortunate to be transfused antigen-positive blood, the former weak antibody would be super-strong next time around !!! Problem solved.

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It sounds as if the "real", actionable result is the 24-hour reading - this should be recorded in the medical files. The "quick-and-dirty" initial test, while not very sensitive, may still be useful in some cases of extreme contamination. It may give the physicians a leg up on treatment. Perhaps a two-field record could be designed? Test #1 = Immediate; Test #2: 24-hr. The interpretation algorithm would include both results.

It's probably all tangled-up in training, competency and proficiency. Maybe an administrative nightmare?

Yeah, I know. I was just being silly, pointing out that sometimes what sounds like a reasonable idea is often impractical and mostly useless. Proposed new policy: Type them once every week for the duration.

Very good point. One could argue that ALL pregnant women should be phenotyped specifically to look for mixed fields.

Concur.

I'm assuming....yes, that gets me into trouble all the time......that you're worried about antigen suppression in pregnant women? Antisera licensed in the USA should have been tested extensively with samples from such patients. If they were unable to correctly phenotype samples from pregnant women, it's unlikely that they would have been approved. As Malcolm points out, the only real troublemakers are the Lewis antigens.

Eek ! I don't like the sound of that. Ethylene oxide (ETO) is a gas used to sterilize materials that can't tolerate other processes (heat/radiation).

I'm certainly not a regulatory expert, but if it is indeed a requirement, I would think that a general "other antigen typing" proficiency would cover you. I can't imagine why one would need proficiency testing for one, or each, typing antiserum.

That was the formaldehyde solution that was used to sterilize reusable dialysis machines in situ. The patients would often make an anti-N-like antibody ("N") that could cause trouble in the AbScr and XM. In the old days, dialysis patients used a LOT of blood. Now, with EPO, they hardly use any. Technically, they didn't have an allergy to the plastics/materials, but rather, as you pointed out, the sterilizing agent. However, it would not surprise me if some patients do develop allergies to today's materials. It seems that everyone is allergic to everything, these days.

Just wondering......several contributors have used the term "direct observation". What would be involved in "indirect observation" ?? Mirrors ? Peripheral vision ? CCTV ?

Fair enough. I thought you meant actual duplicate testing.

Is that a paperwork/clerical check or do you actually test the samples twice?

And remember when the "blood warmer" was a few minutes on the radiator/heating vent ? Good times.

I believe we're all a little guilty of that misdemeanor. It's always good to keep thinking and this forum is an excellent place to throw ideas around. Unfortunately, it is easy to get lost in the matrix when "we" start to second-guess and try to predict the next thing the Regulators are going to pursue. Often, it's a case of trying to fix a problem that doesn't exist (yet).

Think over the premise again. What is the purpose of the CAP program (or any other proficiency) ? Are you testing your facility's ability to get the correct answer (proficiency) or are you qualifying the instruments ? I would argue that it more important to "test" the operators rather than the instruments and therefore the actual instrument used is irrelevant. As a sideline.....what would happen if you got different answers with different instruments? That would be a real pickle.

Please explain how a negative result with (diluted) anti-Fya determines "cell viability". "We test before the old lot expires" - this means you qualify the new panel before putting it into use ?

A fair point, Malcolm. So, I once again pose the rhetorical question: In an acute situation, do you do a "Type & Screen" or a "Type & Panel" ????