I am trying to find a chart or article that tells how long plasma is good for hemostasis testing. The question has arisen about fresh samples and frozen samples. We often get requests for add-on tests and need to know how long is too long. Do you know of a resource that will provide this information? Thanks, Deborah Whetzel MT(ASCP), CLS Supervisor, Children’s Hospital of the King’s Daughters.
Hi, Deborah. I suggest you obtain a copy of Collection, transport, and processing of blood specimens for testing plasma-based coagulation assays, approved guideline, 4th ed. Document H21-A5. Wayne, PA: Clinical Laboratory and Standards Institute, 2008. An H21 sample is posted below. The guideline committee is chaired by Dr. Dorothy Adcock-Funk, and here is a brief summary of their recommendations:
- Coagulation testing specimens should be maintained at room temperature, not refrigerated or iced.
- Specimens for prothrombin time may be held stoppered and uncentrifuged for up to 24 hours after collection.
- Specimens for partial thromboplastin time may be held stoppered and uncentrifuged for up to 4 hours after collection.
- Specimens collected for heparin assay must be centrifuged and the plasma separated within 1 hour of collection.
- When testing cannot be completed within these time parameters, specimens are centrifuged to produce platelet poor plasma and the plasma is immediately frozen and stored at -70°C.
- Specimens collected for platelet aggregometry must be tested within 3 hours of collection, and cannot be frozen.
- Specimens for molecular testing are collected using EDTA and may be refrigerated and stored for up to 72 hours.