Kappa Free Light Chains: A Promising Biomarker for Multiple Sclerosis, Study Suggests

The level of proteins called kappa free light chains in the cerebrospinal fluid (CSF) may be used as a diagnostic marker to identify the presence of Multiple Sclerosis (MS), according to a new study.

Testing for these proteins worked just as well as that measuring oligoclonal bands, or bands of antibodies indicative of inflammation that can be seen when a patient’s CSF is analyzed in the lab. The researchers provide profound evidence that kappa free light chains index and oligoclonal bands testing show similar diagnostic performance in patients with primary progressive MS and, thereby, filled the prior scientific and practical gap in this field. Indeed, the team said kappa free light chains are an emerging biomarker.

The study, titled ‘The Diagnostic Performance of Kappa Free Light Chains in Primary Progressive Multiple Sclerosis: A European Multicenter Study,’ was published as a brief article in Multiple Sclerosis Journal – Experimental, Translational and Clinical.

The diagnosis of MS typically involves a combination of clinical history, neurological examination, imaging studies (such as magnetic resonance imaging or MRI), and laboratory tests — including CSF analysis. Oligoclonal banding is a specific test performed on the CSF to identify abnormal bands of antibodies, specifically IgG, which may indicate an inflammatory or immune response within the central nervous system. While oligoclonal bands are not exclusive to MS, their presence in the CSF can be supportive evidence for a diagnosis.

Prior research has shown that kappa free light chains also accumulate in the CSF during brain and spinal cord inflammation. A study conducted in patients with relapsing-remitting MS indicated that measuring kappa free light chains may be important in the diagnostic workup of suspected MS cases. However, most studies were done in people with relapsing-remitting MS. In the case of primary progressive MS, which involves a gradual worsening of symptoms over time without periods of remission, it was unclear how well kappa free light chains could identify the disease.

To address this question, a team of researchers from multiple MS centers across Europe conducted a study with 174 participants diagnosed with primary progressive MS. The participants, 88 men and 86 women, had a mean age of 52. The researchers calculated a kappa free light chain index based on the protein levels in both the CSF and blood. An index above 6.1 was considered positive.

The results showed that the index was positive in 161 patients (93%), comparable to the 88% of patients with positive oligoclonal bands. The two diagnostic tests were in agreement in the vast majority (90%) of cases. The test also demonstrated a high sensitivity of 93% in identifying primary progressive MS, even across different MS centers.

The measurement of kappa free light chains in the CSF was found to be fast, cost-effective, and showed similar diagnostic sensitivity to oligoclonal band testing in primary progressive MS cases. The researchers concluded that kappa free light chains could serve as an alternative to oligoclonal band testing for patients suspected of having MS.

This study highlights the potential of kappa free light chains as a promising biomarker for the diagnosis of primary progressive MS. Further research and validation are needed to fully establish its clinical utility and broader applicability in MS diagnosis and monitoring.