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A New Question: Overfilled Collection Tubes

A question from Renee Briggs:

My laboratory recently switched to the Greiner Bio-One plastic collection tubes for coagulation.  Greiner has various fill size tubes (2 mL, 3 mL, and 3.5 mL) for their Vacuette sandwich tubes for coagulation.  These tubes have specific fill lines in the tube label and even give a recommendation that the tubes be filled to the line +/- 10%.

My question is my hospital has lots of nurse/physician collected tubes and many time these tubes are sent to the lab incorrectly filled (i.e. outside this +/- 10% of the fill line identified by the manufacturer).  I searched the literature and there are various articles and CLSI documents that discuss the importance of maintaining the correct blood-to-anticoagulant ratio in order to obtain correct results.  However all the articles I found focus mainly on how “underfilled” coagulation tubes can affect patient test results and adjusting the amount of sodium citrate in collection tubes for patients with hematocrits >55%, but I have found none that address the coagulation collection tubes that are “overfilled”.  Obviously many of the grossly overfilled collection tubes come into the laboratory clotted (probably due to inadequate sodium citrate), but what do the experts recommend for those tubes that are slightly overfilled and not clotted?  Should our laboratory reject these solely based on the incorrect blood-to-anticoagulant ratio? If so, how does this overfill issue possibly affect the patient’s coagulation test results?

Hi, Renee. I’ll just toss this out to our participants for a comment. My first scientific wild guess would be to reject all overfilled tubes due to the inadequate AC to blood ratio, but I’d like to hear from folks with some direct experience. Geo

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