Test That Measures Immunoglobulin Chains May Improve Diagnosis of MS

New validated testing method for multiple sclerosis measures kappa immunoglobulin free light chains in cerebrospinal fluid.

A new validated testing method that measures immunoglobulin chains may help improve diagnosis of multiple sclerosis (MS), according to a study published in Mayo Clinic Proceedings.

For the study, the authors noted that an antibody is typically comprised of 2 immunoglobulin heavy chains and 2 light chains—called kappa and lambda. The new validated testing method measures kappa immunoglobulin free light chains in cerebrospinal fluid.

According to the study authors, the test provides an alternative to the commonly used method that detects oligoclonal bands in cerebrospinal fluid, which are proteins that indicate inflammation of the central nervous system.

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

MS, which affects the brain and spinal cord, can cause deterioration and permanent damage of the nerves. Although the root cause of MS is unknown, the disease is known to trigger the immune system to attack myelin, the protective coating that surrounds nerve fibers.

The deterioration of myelin sheaths interrupts signals between the brain and spinal cord, causing symptoms the severity of which are dependent on the amount of nerve damage and the nerves that are affected. These symptoms can be temporary or long-term.

Although there is no cure for MS, treatments can improve recovery time from attacks and can aid in managing symptoms. A diagnostic test that detects oligoclonal bands in cerebrospinal fluid takes approximately 4 hours for analytical processing, which is a labor-intensive process that includes subjective visual interpretation, according to the investigators.

The new study that measures immunoglobulin is able to validate a diagnostic value of 0.1 milligrams per deciliter to evaluate kappa free light chains. According to the Mayo investigators, the results are comparable to diagnostic values from tests that measure oligoclonal bands.

The study authors analyzed serum samples from a retrospective cohort of 702 Mayo patients to determine a diagnostic value that measures kappa free light chains. This value was then validated from samples of a prospective cohort of 657 Mayo patients. Among the more than 1300 patients tested, 12% were diagnosed with MS, according to the study.

"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," said study senior author Maria Alice Willrich, PhD, a Mayo Clinic pathologist, in a press release. "Based on our study data, we identified the optimal performance of the test for a large US-based population."

The investigators estimated a significant cost savings for the new test as well as faster results that are available in approximately 20 minutes.

"The laboratory technologist training can be standardized because of the automation involved in this process, and the subjective visual interpretation of bands and personnel involvement is substantially reduced," Willrich said.