ECTRIMS 2025: Stepping into a new era of precision in MS Diagnosis

When first presented at ECTRIMS 2024, Professor Tintoré, MD, PhD, described this revision as "the most diverse, gender-balanced, and country-balanced diagnostic criteria developed to date." ²  I found it striking how quickly these new guidelines have moved from theory to practice. Session after session, real-world data^3,4 highlighted how the guidelines enable earlier diagnosis. By providing new and accessible tools to aid in the diagnosis of MS, the revised McDonald criteria offer a pragmatic approach tailored to what clinicians can actually request locally.

The Kappa Free Light Chain Index (κFLC index) is one of the new updates to the McDonald criteria. Other changes include the use of the optic nerve as the fifth anatomical location to be examined for lesions, and the detection of Central Vein Sign (CVS) and Paramagnetic Rim Lesions (PRLs). 

Expert insights on κFLC Index

I found the "Meet the Expert" ⁶ session chaired by Professor Arrambide, MD, PhD and Professor Moccia, MD, PhD particularly enlightening, as it made the practical case for the use of Kappa FLC Index crystal clear.

When asked which technique the speakers would recommend if a laboratory must choose between OCB or Kappa FLC Index testing, Prof. Moccia replied without hesitation. "The Kappa FLCs.", he stated, while Prof. Arrambide nodded enthusiastically. He continued, "It’s cheaper, it’s quicker, and it provides a quantitative number."

Prof. Arrambide went on to talk about OCB testing: "In-house tests are much better for detecting oligoclonal bands than commercial ones. Commercial [OCB tests] are better than nothing, but in that case, it might be better to start with the Kappa FLC." 

She then added, "There are at least a couple of studies looking at costs, and yes, as Marcello [Prof. Moccia] said, they [κFLCs] are cheaper."

A key point from this session was that κFLC index accelerates result availability. Results can be reported in 20–30 minutes, and running the test does not require special training.

The scientific community’s enthusiasm for the CSF κFLC analysis and Index was also evident during the poster sessions. With a record number of researchers presenting their work, more than 20 studies investigated the use of the Kappa FLC Index in MS and other neurological diseases.

Access to new paraclinical tests

I appreciated the honesty of the multi-country surveys regarding global access to the new paraclinical tools included in the 2024 McDonald criteria, including κFLC Index. Access is currently uneven, and there’s work to be done^7,8. The barriers are familiar: reimbursement, training gaps, and translation of international guidelines into national consensus⁷.

On the other hand, several presenters argued that the obstacles to availability of κFLC testing may be perceived rather than real. In various sessions, experts highlighted that hematology laboratories already run FLC assays for Multiple Myeloma investigations. Within this situation, adding CSF κFLC testing becomes straightforward. The real barrier may therefore not be a lack of availability of this technology, but awareness. Enhanced collaboration between departments could be key to accessing Kappa FLC testing⁶.

A practical takeaway I loved: if you need κFLC Index, ask your hematology lab⁶.

Conclusions

ECTRIMS 2025 was important to me because it marked the point where precision in MS diagnosis became truly operational. I saw the community shift from discussing the evidence, to implementing it and embracing tools that are faster and more accessible.

Watching the κFLC Index progressing from validation to routine use, supported by guideline inclusion and real-world feasibility, was deeply motivating.