Correspondence To

Abstract

the editor: Sensitivity of serum free light chain measurement of residual disease in multiple myeloma patients We were interested to read the communication from Singhal et al.1 However, there is a misconception that serum free light chain (sFLC) measurement should provide the most sensitive measure of residual disease in all multiple myeloma patients. This appears to have arisen because normalization of the sFLC ratio has been included as one of the criteria necessary for achieving a “stringent complete response ” in the proposed international response criteria.2 In fact, sFLC measurement provides a more sensitive measure of residual disease in some, but not all, myeloma patients. For patients whose tumors produce monoclonal light chains only (LCO), sFLC measurement will generally be mor