Can we estimate the coagulation parameters in stored samples?

Plasma should be stored at room temperature to avoid cold activation of intrinsic hemostasis. Ideal is an interval less than 2h after blood withdrawal. Upon prolonged storage or storage in the cold F12 and prekallikrein are activated.

Yes, I agree -- 2 hours is a relatively 'safe' window.  There are experts who might not believe data for samples more than even 15 minutes old (depending on the nature of the test(s) being run). 

Coag testing is particularly tricky problem with respect to the samples themselves.  Think about the situation with most other blood samples (for anything other than coag) -- you typically use either serum (clotted) or plasma (aggressively anticoagulated with EDTA or heparin).  For coag testing, the sample needs to be anticoagulated, but only just enough so that you can still 'reverse' the anticoagulation and allow the enzymes function in their natural state.  This means that the sample is kept in a fairly unstable state, and coagulation pathway(s) will generally become activated over time. 

You might extend the usable time for a little bit longer by spinning the samples as soon as possible after collection, and harvesting the plasma to get it away from the cells.  The cells themselves are very bad for plasma stability, for a wide variety of reasons.  Of course, this assumes that your particular coag measurements do not rely on whole blood testing.  But even so, 4 hours is probably the upper limit. 

I agree, it has to be done within 2 hrs of collection for absolute values. However, if the assays cant be done in fresh samples and the purpose is to see the relative changes in coagulation between experimental groups, then freshly isolated plasma must be frozen and later, plasma be thawed slowly and then prewarmed at 37'C. Although, the samples must be treated in identical manner (exact thawing time, temp etc for all).

However, this compromised method can be used only to see the relative changes and not for absolute values.

Really it depends on the aim of your study and the tests you are using . Ideally  coagualtion samples should be spun as soon as possible and tested within 4 hrs. If not then samples can be spun to obtain platelet free plasma ( plt <10 ) and then frozen at -20 C for several months. In practical terms however an INR is stable for 24 hrs, but an APTT would not. More specialised testing would have more stringent requirements.

Freezing / thawing activates intrinsic coagulation. -30°C freezing/ 23°C thawing is superior to -80°C freezing/37°C thawing or -80°C freezing/23°C thawing. 37°C should be avoided pre-analytically, it results in artefactual activation of coagulation.

I believe you have some invaluable inputs above. All recommendations are highly dependent on what are you looking for. It would be more helpful if you can be more explicit about what kit you have. Carrying whole blood assays is best done within 2 hours (Speaking of TEGs/Rotems and pretty much anything that need viable platelets) with blood kept at room temp if not 37C and minimal handling. As to plasma based assays you can get away with assessing Fib and some coagulation factors as well as thrombin generation when run as batches after decent periods of storage at -80C but not PT or APTT.  Always wise to take into consideration manufacturers instruction

All the expert colleagues have highlighted important issues in the preparation/storage of plasma for coagulation testing. I would just like to suggest a few references that could help you finding the answers for your specific needs. Of course, there are a lot more out there.

- CLSI. Collection, Transport and Processing of Blood Specimens for Testing Plasma based coagulation assays and Molecular Haemostasis assays: Approved Guideline-5th edition. 2008:H21–A5.

- Adcock Funk DM, Lippi G, Favaloro EJ. Quality standards for sample processing, transportation, and storage in hemostasis testing. Semin Thromb Hemost. 2012;38:576-85.

- Chantarangkul V, Clerici M, Bressi C, Tripodi A. Standardization of the endogenous thrombin potential measurement: how to minimize the effect of residual platelets in stored plasma. Br J Haematol. 2004;124:355-7.

All the answers are correct for me. I could only add that coag is critical in anticoagulated patients with vitamin K antagonists. In this case the timing prothrombin time is done should be as soon as possible, ideally. One could accept up to 2 hours from collection. These is dependable on the half lives of clotting labile factors. Remember F7 has the shortest half live. Hope I have been of use.

Thank you for your valuable comments...

Others have made tremendous contributions.It is wiser to run the test as soon as possible to avoid loosing some labile factors except if you want to study the effect of time on those parameters.Always read the manufacturers instruction very well.Thank you.