Kappa-Free Light Chains in CSF Predict Early Multiple Sclerosis Disease Activity

Objective To investigate whether kappa-free light chain (kappa-FLC) index predicts multiple sclerosis (MS) disease activity independent of demographics, clinical characteristics, and MRI findings. Methods Patients with early MS who had CSF and serum sampling at disease onset were followed for 4 years. At baseline, age, sex, type of symptoms, corticosteroid treatment, and number of T2 hyperintense (T2L) and contrast-enhancing T1 lesions (CELs) on MRI were determined. During follow-up, the occurrence of a second clinical attack and start of disease-modifying therapy (DMT) were registered. kappa-FLCs were measured by nephelometry, and kappa-FLC index calculated as [CSF kappa-FLC/serum kappa-FLC]/albumin quotient. Results A total of 88 patients at a mean age of 33 +/- 10 years and female predominance of 68% were included; 38 (43%) patients experienced a second clinical attack during follow-up. In multivariate Cox regression analysis adjusting for age, sex, T2L, CEL, disease and follow-up duration, administration of corticosteroids at baseline and DMT during follow-up revealed that kappa-FLC index predicts time to second clinical attack. Patients with kappa-FLC index >100 (median value 147) at baseline had a twice as high probability for a second clinical attack within 12 months than patients with low kappa-FLC index (median 28); within 24 months, the chance in patients with high kappa-FLC index was 4 times as high as in patients with low kappa-FLC index. The median time to second attack was 11 months in patients with high kappa-FLC index whereas 36 months in those with low kappa-FLC index. Conclusion High kappa-FLC index predicts early MS disease activity. Classification of Evidence This study provides Class II evidence that in patients with early MS, high kappa-FLC index is an independent risk factor for early second clinical attack.

Automated summary

The study demonstrates that high κ-FLC index is an independent predictor for disease activity in early multiple sclerosis. Among patients with early MS, high κ-FLC index is a significant risk factor for early second clinical attack.