Kappa-free light chain as a practical alternative to oligoclonal bands in the diagnosis of multiple sclerosis

Beckmann Y., Duztas D., Uzunkopru C., Şen S., Arslan G., Gür Vural D., ...Daha Fazla

MULTIPLE SCLEROSIS AND RELATED DISORDERS, cilt.97, 2025 (SCI-Expanded, Scopus)

Özet

Objectives: Kappa free light chains (x-FLC) have emerged as a reliable biomarker for diagnosing multiple sclerosis (MS). Compared to oligoclonal band (OCB) measurement, x-FLC presents distinct advantages, including enhanced accessibility in clinical practice. This study evaluates x-FLC index values in MS patients and explores its potential as a practical alternative to the OCB test. Methods: Cerebrospinal fluid (CSF) and serum x-FLC concentrations were quantified using an immunonephelometry analyzer, while OCB analysis was performed via agarose isoelectric focusing combined with immunoblotting. The cut-off values were set at >= 0.7 for the CSF IgG index and >= 6.6 for the x-FLC index, with values exceeding these thresholds considered positive. x-FLC index values were compared between OCB-negative and OCB-positive patients, between patients with negative and positive CSF IgG index, and across different OCB types. Results: OCB positivity was detected in 82.7 % of patients, whereas a positive x-FLC index was observed in 91.7 %. The IgG index was positive in 51.9 % and negative in 48.1 %. Among patients with a negative IgG index, 84.3 % exhibited a positive x-FLC index. Additionally, CSF x-FLC values were significantly higher in patients with a positive IgG index compared to those with a negative IgG index. On the other hand, patients with type 2 (+) OCBs had higher x-FLC index values than those with negative OCBs. Conclusions: The x-FLC index may serve as a valuable tool for identifying OCB-negative patients with a high likelihood of MS, offering a practical and accessible alternative for diagnostic evaluation.