Kappa Index predicts disease activity and transition to high-efficacy therapies in multiple sclerosis

The Kappa Index has proven its diagnostic value for multiple sclerosis (MS), while its prognostic potential remains to be fully explored. The objective of this study is thus to investigate the value of the Kappa Index at disease onset in predicting disease activity and high-efficacy therapy (HET) initiation.

We enrolled MS patients with available Kappa Index values at disease onset and a follow-up of at least two years. Primary outcome was the time to loss of NEDA3 (no evidence of disease activity-3) defined as the absence of relapses, MRI activity, and disability progression. Secondary outcome was the time to HET initiation.

Of 120 enrolled patients (36 M, 84 F, mean age: 35 ± 11 years), NEDA3 loss occurred in 89 (74 %) by the end of the follow-up period. A total of 98 (82 %) initiated a moderate efficacy therapy (MET); of these, 34 (28 %) transitioned to a HET during follow-up. Kappa Index values above the maximally selected log-rank statistic-derived cut-off of 38 were independent risk factors for NEDA3 loss (HR 1.75, 95 % CI: 1.09-2.80, p=0.021) and HET initiation (3.25, 95 % CI: 1.54-6.87, p=0.002) and also independently predicted HET following MET failure (2.54, 95 % CI: 1.17-5.51, p=0.018).

Elevated Kappa Index values at diagnosis predict disease activity, MET failure and HET initiation and may be a valuable adjunctive tool in identifying patients in need of prompt HET initiation.