In new research, it was suggested that a test measuring kappa immunoglobulin-free light chains in cerebrospinal fluid is a tested alternative for diagnosing multiple sclerosis (MS). 

The results of the study showed that the kappa test was similar in efficacy but much more convenient to run in the laboratory, less expensive, and rapid compared with other commonly used tests. The study confirmed the role of KFLC in the diagnostic work-up for MS. Both KFC index (corrected for blood-CSF barrier permeability) and KFLC/IgG ratio (assessing the overproduction of KFLC in CSF only) demonstrated high sensitivity and specificity towards MS diagnosis. Overall oligoclonal bands (OB) continues to be the gold standard for CSF analysis in MS. 

The researchers suggested that the KFLC index is the most sensible and specific quantitative marker for diagnosing MS and suggested that CSF KFLC/IgG may be used to find whose RIS-CIS patients will convert to MS. (A Faster, Cheaper Diagnostic Test for MS? (medscape.com))