Vall Hebron University Hospital
Dept. of Immunology

Author Of 1 Presentation

Diagnostic Criteria and Differential Diagnosis Late Breaking Abstracts

LB1240 - A kappa free light chain index of 6.6 represents an alternative to positive oligoclonal bands in the 2017 McDonald criteria (ID 2125)



Oligoclonal bands (OB) are part of the 2017 McDonald criteria but their determination is rater-dependent. Kappa free light chains (KFLC) are determined quantitatively and could be an alternative to OB, but a vendor-specific index cut-off is needed.


To compare the proportion of patients with clinically isolated syndromes (CIS) and positive OB and a KFLC index equal or greater than 6.6 (KFLC-6.6, Leurs CE Mult Scler 2020) or 10.61 (KFLC-10.61, Gaetani L J Neuroimmunol 2020). To compare the diagnostic properties of OB, KFLC-6.6 and KFLC-10.61 for 2nd attack and 2017 MRI dissemination in space (DIS) and time (DIT).


MRIs were obtained 3-5 months after the CIS, at 1 year and every 5 years. OB were determined by isoelectric focusing combined with immunoblotting. We selected 228 patients with sufficient data to assess DIS and DIT, OB determination and enough remnant frozen samples to measure KFLC by turbidimetry (Optilite, The Binding Site). We compared the proportion of patients with positive OB, KFLC-6.6 and KFLC-10.61 and the 3-year diagnostic properties for the following outcomes: 2nd attack (n=179) and MRI DIS and DIT (n=192).


Of all patients, 146 (64.0%) had OB, 147 (65.5%) KFLC-6.6 and 137 (60.1%) KFLC-10.61. In total, 130 (57.0%) had OB and KFLC-6.6, 16 (7.0%) only OB, 17 (7.5%) only KFLC-6.6 and 65 (28.5%) had neither. As for OB and KFLC-10.61, 122 (53.5%) had both, 24 (10.5%) only OB, 15 (6.6%) only KFLC-10.61 and 67 (29.4%) had neither. At baseline, the criteria were fulfilled by patients with OB, KFLC-6.6 and KFLC-10.61 as follows: DIS 109/135 (80.7%), 114 (84.4%) and 106 (78.5%); DIT 70/87 (80.5%), 78 (89.7%) and 74 (85.1%); DIS plus DIT 64/78 (81.2), 71 (91.0%) and 67 (85.9); DIS plus OB 109 (100.0%), 101 (92.7%) and 94 (86.2); and McDonald 111/130 (85.4%), 113 (86.9%) and 106 (81.5%). The diagnostic properties of OB, KFLC-6.6 and KFLC-10.61 for 2nd attack were sensitivity 77.8, 85.6 and 78.0; specificity 44.9, 48.3 and 51.7; and accuracy 61.5, 67.0 and 65.4. Results for MRI DIS plus DIT were sensitivity 81.8, 87.9 and 82.6; specificity 66.7, 70.0 and 73.3; and accuracy 77.1, 82.3 and 79.7.


KFLC-10.61 had the greatest specificity and KFLC-6.6 the best overall diagnostic properties. The results were probably due to the higher proportion of positive KFLC patients with DIT compared to those with positive OB, suggesting KFLC-6.6 could be used as an alternative to OB in the McDonald criteria.