Understanding the Clinical Value of the INCAT Disability Score

Body text: Measuring treatment response in chronic inflammatory demyelinating polyneuropathy extends beyond neurological examination alone. As new therapies continue to improve patient outcomes, clinicians increasingly rely on validated functional outcome measures that quantify changes in disability and help define what meaningful improvement looks like over time.

In this NeurologyLive® Special Report, Karissa Gable, MD, FAAN, professor of neurology at Duke University, joins Jeffrey Allen, MD, associate professor of neurology at the University of Minnesota, to discuss findings from a post hoc analysis of the ADHERE and ADHERE+ studies evaluating subcutaneous efgartigimod PH20 (Vyvgart Hytrulo). Throughout the series, the two experts explore how lower disability thresholds may reshape treatment expectations and long-term management of patients with CIDP.

This episode focuses on the Inflammatory Neuropathy Cause and Treatment (INCAT) disability score, one of the most widely used outcome measures in CIDP clinical trials. Gable and Allen discuss what the scale captures, why a score of 0 or 1 reflects minimal disability, and how these outcomes translate into meaningful improvements in independence and daily function for patients.

Karissa Gable, MD, FAAN:

To understand the INCAT score and what a score of 0 or 1 actually represents, you first have to take a step back and think about how we use all of these outcome measures.

The INCAT score is commonly used in clinical trials, including the ADHERE study, as a primary outcome measure because it provides an objective assessment of a patient's clinical symptoms. We use the neurological examination and patient-reported symptoms as part of our clinical judgment to understand how patients are responding to treatment over time, and then we use the INCAT score, along with other outcome measures that are often secondary end points, to objectively assess treatment response and determine whether treatment adjustments may be needed.

Specifically, the INCAT score evaluates upper and lower limb disability on a scale from 0 to 10, with 10 representing the greatest disability. A score of 0 in the arms means there are no upper extremity limitations, while a score of 0 in the legs means walking is unaffected. Naturally, that is our goal.

A score of 1 can reflect either minor upper extremity symptoms or mild lower extremity involvement. In the arms, patients may have numbness or tingling that does not interfere with activities such as buttoning clothes, using zippers, brushing their hair, using a knife and fork together, or handling small coins. In the legs, a score of 1 means walking is affected, but the patient remains independently ambulatory. You can imagine that reaching a score of 0 or 1 represents very minimal manifestations of the disease, which is why it is such a clinically meaningful outcome.

Jeffrey Allen, MD:

Yeah, I don't have much to add to that. The INCAT score has been around in some form for a couple of decades. It ranges from 0 to 10, with higher scores representing greater disability. Five points are assigned to upper extremity function and five points to lower extremity function, for a total possible score of 10.

We also know that a 1-point change on the INCAT score is clinically meaningful. It has become one of the most commonly used primary outcome measures in CIDP clinical trials over the past several years, and it is also a useful tool in clinical practice. Reaching a score of 0 or 1 indicates that a patient is doing very well. It doesn't necessarily mean they are symptom free, but it does mean they are functioning independently.