Dear Center for Phlebotomy Education:

Mixing tubes properly is a big problem in our facility. With different numbers of inversions for different tubes, it's hard to teach and hard for our staff to retain, much less implement. We need an easier way to get the point across that will actually be incorporated into our staff's practices. If I could just simplify our procedure manuals to say that all tubes should be mixed 10 times, that would solve the problem. But some publications say 3-5 times, some 5-6, and some 8-10. I don't want to cause problems with sample quality, but we need some kind of standardization that works.  What should we do?

Our response:

We can understand your interest in simplifying the mixing sequence to get better compliance. But it's really not as complicated as you think.

Your reference that some say 3-5 inversions is likely pertaining to citrate tubes. It's typical for manufacturers to limit inversions for coags because excessive agitation can activate platelets, which would then release factors that could alter coag results. Also, sodium citrate is a liquid additive, which mixes much more readily, and doesn't require the same number of inversions to prevent coagulation as tubes with dry anticoagulants that adhere to the walls of the tube.

But there are good reasons some tubes should not be subjected to that many. So you really wouldn't want to apply a 10-inversion rule across the board. Nor would you want to adopt a 5-inversion rule to tubes that have dry anticoagulants for the opposite reason. The lower number might lead to rejected samples because of clotting if all the additive isn't mixed off the walls of the tube into the sample.

So you really need to apply whatever the manufacturer recommends. That's likely to be 5-8 for all tubes except sodium citrate, which requires only 3-5. Tubes for Quantiferon, however, require vigorous shaking. 

So there really can't be one recommendation that works for all tubes. That's just the nature of preanalytic quality. If you're getting a lot of clotted tubes due to inadequate mixing, you need an inservice or remedial training for those whose technique is contributing to the problem. Rejected samples are a huge problem for every lab. In the case of clotted samples, it's entirely preventable.

Got a challenging phlebotomy situation or work-related question? Email us your submission at [email protected] and you just might see it as a future case study. (Names and identifiers will be removed to assure anonymity.)