The title says it all. My work is in a tizzy trying to figure this out (we keep getting conflicting answers). CLIA (I don’t know if that is the correct abbreviation. They are a body that certifies clinics and such) has told one of our customers that they are spinning urine too quickly. They state the speed should be 1500 to 2000 RPM, while our customer has been using 3000 to 3400 RPM. Has any damage been caused to the samples if this is indeed the wrong speed? And just what speed should be used?
I’m sure someone will come along with the right answer. Until then, can you enlighten me as to why you spin urine to start with?
According to my boss, urine has sediment in it (red blood cells, white blood cells, etc.) They spin it to seperate all of that. There is a longer, more drawn-out explanation, but it is over my head, I’m afraid.
Examination of urine sediment is a common procedure, and requires centrifuging. The speed will depend on the centrifuge; the constant here is the number of Gs. I have seen numbers from 450 to 1700 Gs; I would err on the low side, since damaging the sediment particles can make examination worthless, but you can always spin it more.
Nametag’s nailed the problem here. What’s important is making sure that the G force (aka RCF) is correct for the sample being prepared. The RPM required to achieve this RCF will differ depending upon the radius of the centrifuge rotor being used.
Check out this handy calculator for figuring RCFs and RPMs:
According to this site:
a 5 minute spin at a RCF of 400 is ideal for urine sample centrifugation.
Punching various numbers into the calculator, it’s clear that spinning the samples at 3000+ RPM is probably excessive for most clinical centrifuge rotors. I’ve never spun down urine before, but I’ve done plenty of blood and bone marrow and I can tell you that cell damage is a definite possibilty at too high a RCF. If they’re looking for cells in the sample, then this could be a problem. The lower RPMs you stated are probably about right.
So, liirogue, it appears urine luck! Stochastic is the whiz with the answers.
In my lab we spin urines at 1800 rpm for five minutes. I don’t think you’d see much cell damage at 3000 rpm but I’d think you’d certainly get fragmenting of casts to some degree.