New B Cell-Related Markers in MS Diagnosis: The Tunisian Experience

• Published in: Multiple sclerosis and related disorders 2023-03, Vol.71, p.104273, Article 104273
• Main Authors: Feki, Sawsan, Dammak, Mariem, Sakka, Salma, Ali, Yesmine Ben, Mejdoub, Sabrina, Bouattour, Nadia, Hachicha, Hend, Mhiri, Chokri, Masmoudi, Hatem
• Format: Article
• Language: English
• ISSN: 2211-0348; 2211-0356
• DOI: 10.1016/j.msard.2022.104273

The contribution of the CSF investigation was reaffirmed again in the recently revised MS diagnostic criteria. Considering the limitations in routine biological testing, we aimed to optimize the MS diagnosis algorithm by testing the performance of the new B cell-related markers (Ig free light chains (FLC) and CXCL13 (B-Cell Attracting chemokine1) metrics) for the detection of the intrathecal humoral response in the Tunisian population. During the study period, 300 paired CSF and serum samples were collected from patients (n=150) with MS (n =80) and non-MS inflammatory disease of the CNS (n =70) and addressed to the Laboratory for routine investigation (IgG Index, OCB detection). All included individuals benefited from FLC (κ and λ) measurement in CSF and serum for different metrics calculation (κ/λ ratio, FLC Indexes, FLC IgG Indexes, κFLC intrathecal fraction (IF)) using formulas and the “FLC-κ statistics and graphic program”. CSF Levels of CXCL13 were also determined. All FLC metrics in CSF were higher in patients with MS than in the control group, as well as in OCB-positive than OCB-negative patients. As expected, κFLC-related parameters, in particular κFLC index and the intrathecal fraction κFLC IF had the highest accuracy for MS diagnosis (AUC:0.910 and 0.926; respectively). κ Index showed the best performance (sensitivity 83% and specificity 91.7%) at a cut-off of 14,9. CXCL13 level in CSF was also higher in the MS group than the non-MS group (p=0.029) and OCB-positive (p