George occasionally receives questions about factor substitution assays. We coagulationists of a "certain age" can recall preparing barium sulfate or aluminum hydroxide "adsorbed" plasma, aged plasma, and serum, then performing mixing studies on prolonged PTT patient plasmas. We mixed the patient plasma 1:1 with pooled normal plasma and the adsorbed and aged plasma and serum,
respectively, predicting that the results would provide indication of a single coagulant factor deficiency. Recall that---
- Pooled platelet-free normal plasma (NP ) provides all the coagulation factors at or near 100 IUs/dL.
- Barium sulfate adsorbed plasma provides fibrinogen and factors V, VIII, XI, XII, and XIII; adsorption removes the vitamin K-dependent factors II, VII, IX, and X.
- Aged plasma provides fibrinogen, II (prothrombin), VII, IX, X, XI, XII, and XIII; aging removes the "labile" factors V and VIII
- Serum provides VII, IX, X, XI, and XII; fibrinogen, prothrombin, and factors V, VIII, and XIII are fully consumed during clotting.
While we continue to perform NP mixing studies as routine acute care assays, adsorbed and aged plasma and serum have long disappeared. I recall George King Bio-Medical Inc. shipped their last lot of these reagents in 1991 or 1992, and I don't believe our sponsor, Precision BioLogic Inc. ever prepared or distributed these reagents.
Why? We'd perfected and automated relatively reliable and simple one-stage clot=based factor assays, the substitution assays often gave us equivocal results, and besides, most of the congenital coagulopathies were defieciencies of either factor VIII, IX, or XI.
Do you recall using factor substituion assays? If so, do you have any stories to tell? Did the approach work for you? Do you know of any current application for the substitution reagents? Please send George your stories and comments using the comment function or by sending to firstname.lastname@example.org. Thank you.
Ref: Fritsma GA. Clot-based assays of coagulation, Chapter 4. In Corriveau DM, Fritsma GA. Hemostasis and Thrombosis in the Clinical Laboratory 1988, Lippincott, Phildelphia.