Serum free light chains and oligoclonal bands in patients with multiple myeloma and autologous stem cell transplantation.

Background: To establish stringent complete remission (SCR) in patients with multiple myeloma (MM), it is currently recommended to obtain a normal serum free light chains (sFLC) ratio. The appearance of serum oligoclonal bands (OB) after autologous stem cell transplantation (ASCT) is considered a favorable prognostic factor. The objective of this study was to examine sFLC for assessing SCR in patients with MM, and ASCT with OB. We also examined how capillary electrophoresis (CE) compares with agarose gel electrophoresis (Aga) in identifying oligoclonal bands.

Methods: Out of 238 patients studied in our institution between April 1992 and December 2008 a serum protein electrophoresis (SPE) was performed by means of CE and sFLC determination on 37 patients with MM in complete remission (CR), ASCT and OB presence were assigned by conventional Aga electrophoresis and IF.

Results: Statistically significant differences (SSD) were found when comparing CE vs. Aga, regarding BO visualization in SPE, favoring the latter. In connection with sFLC, the group of patients with an abnormal ratio presented elevated values in the γ-globulin zone of the SPE, whereas the group of patients with a normal ratio of sFLC presented with normal values resulting in SSD between the groups.

Conclusions: It is essential to perform immunofixation to certify the presence of OB, especially if CE is used as it is difficult to distinguish them using this method. A normal sFLC was observed in most of the patients with OB and normal values of the SPE γ-globulin zone. The above-mentioned information might demonstrate a limitation of sFLC test in SCR evaluation for patients with MM, ASCT and CR if OB has been detected.