The cause of turbidity in lyophilised plasmas and its effects on coagulation tests.
OBJECTIVE
To investigate the cause of turbidity in reconstituted lyophilised plasmas and to determine its effect on coagulometers.


METHODS
The turbidities of 20 normal plasmas and 16 reconstituted lyophilised plasmas were determined by comparing a 1 in 4 dilution in distilled water with a standard suspension in an Aminco Fluorocolorimeter (American Instrument Co) in nephelometric mode. The turbidities of five other plasmas were determined before and after lyophilisation. The turbid components of fresh and reconstituted lyophilised plasmas were studied using electron microscopy. The effects of turbidity on five types of coagulometer were determined by adding varying concentrations of a turbidity enhancing material.


RESULTS
Reconstituted lyophilised plasmas were more turbid than normal plasmas, because of agglomerated liposomes. Serum depleted of chylomicrons and very low density lipoproteins was not rendered more turbid by lyophilisation. Three out of five types of automated coagulometer tested gave activated partial thromboplastin times which were appreciably affected by plasma turbidity. One of the instruments was unable to detect a clot in a moderately turbid plasma. A second instrument gave results which were significantly affected by turbidity. Turbidity of the substrate plasma did not affect specific factor VIII assays in two types of coagulometer.


CONCLUSIONS
Lyophilisation of plasma induces turbidity due to the agglomeration of lipids. Such turbidity can affect the results of coagulation tests. Suppliers of lyophilised plasmas should be aware of this problem.
Hirst
C F
CF
United Kingdom Reference Laboratory for Anticoagulant Reagents and Control, Withington Hospital, Manchester.
Poller
L
L
D001780:Blood Coagulation Tests; D005612:Freeze Drying; D006801:Humans; D008074:Lipoproteins / Q000097:blood; D008081:Liposomes; D008854:Microscopy, Electron; D009391:Nephelometry and Turbidimetry; D010314:Partial Thromboplastin Time; D010949:Plasma
D008074:Lipoproteins; D008081:Liposomes