Rethinking How We Measure Hand Function in IBM
For many people living with inclusion body myositis (IBM), the first changes are easy to overlook. A shirt button takes a little longer to fasten. A key doesn’t turn as easily in the lock. Picking up coins from a table becomes frustrating. These are small moments—until they aren’t. Over time, these everyday difficulties add up, quietly reshaping daily life.
Researchers have long known that hand weakness is a hallmark of IBM. But a growing body of research suggests something equally important: We may not have been measuring that weakness in the most meaningful way.
Not just strength alone
Traditionally, doctors and researchers have relied on a standard questionnaire called the IBM Functional Rating Scale (IBM‑FRS) to track disease progression. It asks patients to rate their ability to perform certain activities, including those involving the hands.
But IBM progresses slowly, and the changes can be subtle. For patients, there’s often a wide gap between “no problem” and “serious difficulty”—a gray area where real-life challenges exist but may not be captured by standard scoring. That raised an important question: Are we missing important changes because we’re not asking the right questions?
To explore this, researchers at Washington University in St. Louis took a closer look at how hand function is measured.
In one study, more than 80 people with IBM participated in a detailed evaluation of hand strength and function. Researchers measured how strongly participants could grip and pinch, while also asking them to complete different questionnaires. One was the familiar IBM‑FRS. The other was a newer set of questions focused on very specific tasks—things like buttoning a shirt, opening a jar, or turning a key. The difference turned out to be striking.
While the traditional scale often showed little change until weakness became severe, the task-based questions revealed much more subtle shifts in ability—changes that patients were already experiencing in their daily lives. In other words, patients themselves were providing one of the most sensitive measures of disease progression.
Not all strength is the same
The study also highlighted something else important: Hand strength isn’t just one thing.
Grip strength—the ability to squeeze—is different from pinch strength, which relies on the thumb and fingers working together. In IBM, these functions can decline differently because they involve different muscles.
“We measured pinch with the thumb and index finger using a paper-thin force transducer, so people were actually using a pinching motion,” says Dr. Chris Weihl, who served as principal investigator for these studies.
Dr. Weihl’s team found that measuring both grip strength and pinch strength gives a clearer, more complete picture. Relying on just one risks missing important changes.
They also observed that declines in hand strength tend to be greatest in the earlier years of the disease, before leveling off later on. This makes early, sensitive measurement even more critical, especially for clinical trials.
Watching function in action
A second study approached the question from a different angle. Instead of relying mainly on strength measurements or questionnaires, researchers focused on what people could actually do with their hands. Participants were asked to perform real-world tasks like handling small objects, completing timed dexterity tests, and using their hands in ways that mirror daily life. These performance-based tests offered a window into the practical impact of IBM.
Not surprisingly, they showed that many individuals struggle with fine motor skills, often losing independence in small but meaningful ways. But these tests also revealed something encouraging: they provided a clear, measurable link between strength and real-life function. Grip strength, questionnaire responses, and performance tests were all related, but each captured a slightly different aspect of the experience of living with IBM.
Taken together, these studies point toward a simple but powerful idea: No single measurement can fully capture hand function in IBM. Strength tests, patient-reported experiences, and real-life performance assessments each tell part of the story. When used together, they create a fuller, more accurate picture of how the disease affects daily life.
Why this matters
This matters far beyond the research setting. In clinical trials, the ability to detect small changes can make all the difference. If a measurement tool isn’t sensitive enough, a treatment that is actually helping might appear ineffective.
“These studies are also important for current clinical trials, many of which focus on ambulatory patients,” says Dr. Weihl. “Sensitive hand-function measures may help capture meaningful outcomes for non-ambulatory patients as well.”
By improving how hand function is measured, researchers can better track disease progression, more accurately evaluate potential therapies, and design trials that reflect what truly matters to patients. And what matters most is not just muscle strength—it’s function. It’s the ability to hold a fork, button a shirt, write a note, or open a door. It’s independence in the smallest, most personal parts of life.
As research continues, one message is clear: To understand IBM, we need to listen to patients, measure carefully, and look closely at how people live, not just how strong they are. And in doing so, we move closer to treatments that don’t just change numbers—but make a real difference in everyday life.
Conrad (Chris) Weihl, MD, PhD, is Professor of Neurology and Head of the Neuromuscular Section at Washington University School of Medicine in St. Louis. Dr. Weihl and his team from Washington University in St. Louis recruited TMA members at several Annual Patient Conferences to serve as research subjects for these studies.
Read the research:
Optimizing hand-function patient outcome measures for inclusion body myositis
Exploring hand and upper limb function in patients with inclusion body myositis (IBM)
