Diagnostic value of immunoglobulin free light chains at the debut of multiple sclerosis

Abstract

To evaluate the diagnostic value of determination of free immunoglobulin light chains (IgG) in the debut of multiple sclerosis (MS). Data from 226 patients, including 111 patients with clinically isolated syndrome with conversion to multiple sclerosis within the first 2 years of the disease (group 1), 49 patients with clinically isolated syndrome who did not develop multiple sclerosis within the first 2 years of the disease (group 2), 20 patients with other inflammatory diseases of the central nervous system (group 3) were analyzed. The control group consisted of 46 patients with non-inflammatory diseases of the central nervous system. The clonality of immunoglobulins in the CSF, concentration of kappa and lambda free light chains and their ratio were studied. Concentrations of free light chains were significantly higher in the first group in comparison with group 2 and the control group, but didn't differ from group 3. In group 3, concentrations of free light chains were significantly higher compared to group 2 and controls. In oligoclonal-positive patients with clinically isolated syndrome (groups 1 and 2), concentrations of kappa and lambda free light chains were significantly higher than in oligoclonal-negative patients. The production of free light chains in patients from the first group was considerably higher than in group 2 regardless of the oligoclonal status. The concentration of kappa chains and quotient of kappa free light chains in the CSF had the best diagnostic characteristics. Their use, along with the evaluation of IgG clonality, reduced the risk of false-negative results by 50%. Regardless of other factors, elevated concentrations of kappa chains increase the likelihood of MS diagnosis by 9.718 times. The use of free light chains as a laboratory marker can increase the accuracy of MS diagnosis. These markers can help indirectly assess the risk of transformation of a clinically isolated syndrome into definite multiple sclerosis within the first 2 years of disease.