My laboratory does quite a bit of outpatient clinic work. The lion’s share are prothrombin times. We store these at room temperature, but they can be delayed up to 8 hours before testing. I have heard that samples that are held uncentrifuged until testing preserves integrity better than those that are centrifuged immediately and left in the primary tube capped. Any thoughts?Hello, and thank you for your question. Specimens collected in 3.2% sodium citrate for prothrombin times (PT) can be held at room temperature for up to 24 hours with no deterioration. There are no studies comparing centrifuged versus uncentrifuged specimens for their integrity, which gives me the freedom to speculate that it makes no difference. I checked with Dorothy Adcock-Funk, MD, Medical Director for Esoterix Coagulation and an author of CLSI Guideline H21-A5, who agrees. However, given that I’ve never seen the idea tested, you may want to try a confirmatory experiment using duplicate tubes, one centrifuged and one uncentrifuged. I’d be surprised to learn there is a difference. Geo.