A quick and noninvasive test, called the triple-timed up-and-go test, is a reliable and reproducible tool to assess muscle weakness in Lambert-Eaton myasthenic syndrome (LEMS) patients, according to a study.
Results from the study will be presented at the upcoming American Association of Neuromuscular & Electrodiagnostic Medicine (AANEM) Annual Meeting, taking place Oct. 10-13 in Washington, D.C.
Shruti Raja, MD, an assistant professor in the neuromuscular division of the Department of Neurology at Duke University, will discuss the results in a presentation, “Validation of the Triple timed Up-and-Go Test for Clinical Assessment in Lambert-Eaton Myasthenia Patients.”
Currently, there are no validated and practical tools of quantifying functional disability in LEMS patients.
The timed up-and-go (TUG) test measures the time it takes for a patient to rise from a chair, walk a short distance, and return to the chair. The test has been mainly used to assess the mobility of Parkinson’s disease patients and among the elderly.
The newly developed 3TUG test, was designed as a simple and noninvasive test to measure disease severity in LEMS patients, who exhibit muscle weakness that impairs their ability to walk, climb stairs, and stand up from a chair.
The 3TUG test begins with the participant sitting in a high straight-backed armchair. A colored line on the floor is placed within 3 meters of the front of the chair and is marked with an “X” at its center.
Participants are instructed to get up from the chair, walk at their normal pace to the line, step on the X, turn around, walk back to the chair, turn around, and sit down. This is repeated three times without rest.
The 3TUG test time is the average of the three lap times.
To assess the potential of the 3TUG test and how it correlates with other measures of disease severity in LEMS, researchers analyzed data from a Phase 2 clinical trial (NCT01511978) called DAPPER.
The study, sponsored by Jacobus Pharmaceutical, tested the safety and effectiveness of amifampridine (3,4-DAP) in LEMS patients and evaluated their outcomes using the 3TUG test as a primary measure.
They tested the 3TUG test’s reproducibility, meaning its ability to replicate the same result in a retest. The results showed that the 3TUG test had excellent reproducibility, with less than 20% variability among the tests in the group of LEMS patients.
Moreover, researchers registered a significant correlation between the 3TUG times and patients’ scores on the Lower Extremity Function Scale — a questionnaire of 20 questions on a person’s ability to perform everyday tasks — in patients undergoing and in those who discontinued treatment with amifampridine.
“Worsening of ≥3 points on the Weakness Self-Assessment Scale corresponded with a ≥74% prolongation of 3TUG time (i.e., worsening),” the researchers said. A more severe worsening (what researchers called “much worse”) corresponded with a 94% increased 3TUG time.
For patients who discontinued amifampridine, an increase in 3TUG test timing correlated with lower scores in a test that monitors muscle function, called compound muscle action potentials.
“These findings indicate the 3TUG is a valid measure of disease severity in LEMS patients,” the researchers concluded.
Raja is the runner-up for Best Abstract at the 2018 AANEM Annual Meeting.