Can lithium-heparin plasma be used for protein electrophoresis and paraprotein identification?

Lithium-heparin plasma is the most commonly used sample type in many hospitals, but it has been suggested that it is not suitable for protein electrophoresis due to the presence of fibrinogen, which can potentially mask a paraprotein band or be misconstrued as one. Here we aimed to demonstrate that lithium-heparin plasma samples could be used for protein electrophoresis and paraprotein typing without or with ethanol treatment to remove the fibrinogen.

A lithium-heparin sample from a patient with IgGlambda, IgGkappa, IgAlambda and IgAkappa myeloma, a non-specific polyclonal increase and a serum control were treated with ethanol prior to protein electrophoresis. Immunofixation electrophoresis was undertaken to investigate the effect of ethanol treatment on immunoglobulin and light chains. Nephelometry was undertaken to investigate whether ethanol treatment affected the quantification of IgG levels. Densitometric evaluation of proteins after electrophoresis was used to study whether ethanol treatment affected other serum proteins. An audit was also undertaken to ascertain the magnitude of the potential interference from the fibrinogen band in heparinized samples.

Ethanol treatment significantly but incompletely removed the fibrinogen in lithium-heparin plasma samples and did not affect the integrity of any of the proteins investigated. Even without ethanol treatment, lithium-heparin plasma can be used for protein electrophoresis and paraprotein identification as the instances of interference between fibrinogen and paraproteins was low (2.3%). In rare cases where there is uncertainty or ambiguity, immuno-fixation electrophoresis is recommended. This report has implications in terms of reducing costs and turn-around time as it prevents the need for requesting another serum sample from patients. This may be one step towards a universal sample for all tests.