digital timer in Blood bank

[larevalo]

Does anyone knows the acceptable range for critical timer? And acceptable temperature of the freezer? Thanks

[Lcsmrz]

Acceptable range for a timer is dictated by the event you are timing. If it's an manual enzyme reaction, it could be very compact, whereas if you're timing BB tube incubations at 37C, you have a little leeway. We use ~2% as an acceptable deviation from out NIST device (2 sec every min) for BB events, and we've switched to all digital devices to achieve that. My procedure manual specifies acceptable ranges (37 +1 C, 10-15 min, etc).

Freezer range is determined again by the application. If you're storing frozen plasma, -18C or less is what you're shooting for. However, if in the same freezer you're also storing some reagent that needs -20C or less, then that becomes your standard. And if you're trying to store frozen plasma and a reagent needing -10C to -20C, you only have a 2C range to operate within -- difficult to maintain!

Same with using a a BB Storage Refrigerator to store blood products (1-6C) and RhIg (2-8C). Your operating range is really 2-6C, and with alarm activation temps a half degree from the the edges, your cabinet must consistently hold 2.5-5.5C.

And it gets even trickier when using a backup refrig or freezer. It has to meet the same operating criteria as the original.

[NedB]

I think larevalo is asking for acceptable ranges for checking the timers and thermometers. There are no acceptable ranges posted for timers (that I have seen), so we use what is acceptable all over the lab, +/- 5%. We check all timers for this range, timers, centrifuges, plasma thawer. As for the thermometers, we use the AABB criteria, +/- 1 degree for all thermometers and +/- 2 degrees for charts. The simplest way to check timers, of course is to use the nist.gov site. All of our inspectors have accepted this.

[David Saikin]

I think that only analog timers need to be checked. Digital is usually exempt . . . because of the nature of digital.

[NedB]

Must respectfully disagree with David Saikin. True, newer timers seem to have a circuit that makes them stop timing when the battery runs low. This is probably not true of older timers. In addition, timers on plasma thawers and centrifuges are also digital, but you wouldn't not check these, would you? Here we check thawer and centrifuge timers quarterly against bench timers and check the bench timers themselves annually.

[David Saikin]

The standards require timer checks on analog timers, not digital. Digital, if battery operated, always runs until insufficient power - no decrease in timing. If plugged in, there should be no problems at all. Digital is based on osciallations of quartz at a certain frequency (I think) - it does not vary as long as powered. We never check digital timers, never been cited (AABB/CAP/FDA)- quote the standard. Further, I have had CAP inspectors who "thought" that I should be doing as intimated above . . . CAP Central agreed with me.

Edited July 30, 2008 by David Saikin
additional info

[Mabel Adams]

I want to resurrect this thread to ask a slightly new question. If you are a transfusion service that gets digital timers that come with a calibration certificate, do you check to make sure they keep the right time before putting them into use? Do you verify the temperature of thermometers that come with a certificate? If so, why? I am not CAP inspected, but JC, AABB & FDA so am most interested in those regulations or technical justification.

[butlermom]

I want to resurrect this thread to ask a slightly new question. If you are a transfusion service that gets digital timers that come with a calibration certificate, do you check to make sure they keep the right time before putting them into use? Do you verify the temperature of thermometers that come with a certificate? If so, why? I am not CAP inspected, but JC, AABB & FDA so am most interested in those regulations or technical justification.

No, if the timer or the thermometer is brand new (and comes with a certificate) I see no reason to verify prior to putting them into use. However, your question gives me pause to think about this some more. I guess an argument for verifying could be to ensure that nothing got "jolted" or "misaligned" during shipment. I'll be interested to read other replies. BTW, we are CAP and JC inspected only.

Kathryn

[Eagle Eye]

we check our thermometers annually and before put into use(regardless of indated certificate)

[lirpammt]

According to the AABB Technical Manual in Appendix 1-4; timers should be checked twice yearly. Our timers are calibrated and NIST calibrated but they state on their certificate that there is no exact way of determining how long the calibration will maintain.

It is also noted in the AABB manual that for each new piece of equipment...performance qualifications must be performed.

What standard(s) gets around this?

Thanks!

[SMW]

The AABB Tech Manual is a TEXTBOOK and does not necessarily represent the Standards, regulations, etc. and may simply be the opinions of the author of the particular chapter.  You need to ensure you are complying with the regulations and not necessarily the Tech Manual. 

[lirpammt]

I understand but the Standards just say to do it at prescribed intervals with no specifications. The manual suggests every 6 months. My problem is that it has been stated that digital timers do not have to be done...

[Sandy L]

We do not calibrate our digital timers on receipt.  Ours come with a calibration certificate good for 2 years.  When the calibration date is up we remove from service and replace.  Many years ago we re-calibrated after the expiration date but they are quite inexpensive so stopped doing it. 

[AMcCord]

I check new stuff just to make sure it survived shipping - the jostle, crash theory. Last year I got a new thermometer in, certificate and all, and it did not check - the temp was way off.

[R1R2]

I check new stuff just to make sure it survived shipping - the jostle, crash theory. Last year I got a new thermometer in, certificate and all, and it did not check - the temp was way off.

Me too, we sent it back to the manufacturer.