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Centrifuge calibration


Tympanista

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     I am revising a 30 year old procedure for centrifuge calibration based on the procedure in the Technical Manual.  When you check the tubes to see if "the cell button is clearly delineated and the periphery is sharply defined, not fuzzy" is this for the positive tubes only?  I have tried the immediate spin procedure taking the centrifuge time all the way up to 2 minutes and the cell button is still not clearly delineated for the negative tubes.  I reviewed the calibration records from the past few years and they have been choosing a centrifuge time of 20 seconds based on the fact that the cell button was not clearly delineated in the negative tubes at 10 and 15 seconds, but it supposedly was at 20 seconds.  I really don't believe it has ever been clearly delineated at 20 seconds.  That was just the suggested time from the manufacturer, so I think they have been "making it work" each time a calibration was done.  Should the cell button be clearly delineated for the negative tubes or should we only be looking for a defined cell button in the positive tubes?  My centrifuges meet all of the other criteria in the Technical Manual (clear supernatant, cell button easily re-suspended, etc.) using only a 10 second spin, so I was just curious about how other facilities interpret the procedure.

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From our experience, both negative and positive reactions should give a reasonable clearly delineated button after 15 seconds or so.  (If you spin patients for 2 minutes, I would think that you would end up with a lot of "snotty" false positives!)

Is your centrifuge running at the correct centrifugal force?  Is it vibrating too much?  You may want to try the process with another centrifuge just to see if there is something wrong with what you are working with in the Blood Bank.

Scott

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SMILLER:  Thanks for your response.  I only spun the tubes for 2 minutes to see if the cell button in the negative tubes would be more clearly delineated than it was at 20 and 25 seconds.  Our spin times are set at 20 and 25 seconds, depending on which centrifuge we're using.  We have 2 cellwashers and a regular centrifuge that we use in our Blood Bank, and none of them are giving us a good cell button with the negative tubes.  I'll have to follow up with our Clinical Engineering staff to find out how often they check the RPMs.

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