Mayo Study Shows Kappa Free Light Chain Tests of Cerebrospinal Fluid Could Be Used to Diagnose MS

Mayo Clinic researchers have validated a new antibody test to diagnose multiple sclerosisthat may reduce cost and turnaround time compared to standard testing.

Maria Alice Willrich, Ph.D., a Mayo Clinic pathologist and senior author of the study published in Mayo Clinic Proceedings, and colleagues compared the standard diagnostic test that detects oligoclonal bands (OCB) — proteins in the cerebrospinal fluid that indicate inflammation in the central nervous system— with measuring kappa free light chains, also in the cerebrospinal fluid.

Kappa free light chains are a component of antibodies. Blood tests of free light chains are used in the diagnosis of multiple myeloma and other plasma cell disorders. 

"Kappa free light chain measurement in cerebrospinal fluid is relatively new, and various published studies have attempted to decide what is the best medical decision point for optimal performance of the test," Willrich said in a news release. "Based on our study data, we identified the optimal performance of the test for a large U.S.-based population."

OCB testing has a track record but also has drawbacks. It is labor intensive, requiring about four hours of analytical processing. It also involves subjective visual interpretation, noted Willrich. By contrast, results of a kappa free light chain test are available in about 20 minutes. Kappa free light chain testing stands to produce a “significant” cost savings, Willrich said.

Willrich and colleagues tested 702 retrospective and 657 prospective paired cerebrospinal /serum samples from residual waste samples of physician-ordered OCB tests. Charts were reviewed by a neurologist blinded to kappa free light chain results,.

Specificity and sensitivity for MS diagnosis were evaluated to establish a diagnostic cutoff value for in the retrospective cohort and then validated in the prospective cohort.

Of the more than 1,300 patients, 12% were diagnosed with MS.

“The KCSF (kappa free light chain measurement of cerebrospinal fluid) value of 0.1 mg/dL is a valid alternative to OCB testing, offering a standardized quantitative measure, eliminating human error, reducing cost and turnaround time, with no significant difference in sensitivity and specificity,” Willrich wrote.

"Among the advantages of kappa measurement is that it's a much easier test to run in the laboratory," echoed Ruba Saadeh, a research fellow in neuroimmunology in Mayo Clinic's Department of Laboratory Medicine and Pathology, and the study's first author. "Our findings represent a cost savings as well as an automated alternative to the arsenal of tests used to diagnose multiple sclerosis.”

In addition, laboratory technologist training can be standardized because of the automation involved in the process, according to Willrich.