An ALS clinical trial measures the effect of a treatment on some “outcome measure,” such as breathing function (as measured by vital capacity), or overall function (as measured by the ALS Functional Rating Scale-Revised, or ALSFRS-R). One challenge in clinical trials is that the score on a particular outcome measure may fluctuate over short periods, even while declining over the long run. This means that clinical trials must be long enough to allow the fluctuations to even out, to see the true effect of a treatment. A new ALS Association-funded study from Dr. Patricia Andres of Massachusetts General Hospital and colleagues shows that the scores on a novel muscle strength test fluctuate less than either vital capacity or the ALSFRS-R, and thus may be useful in shortening clinical trials.
The new test, called ATLIS (Accurate Test of Limb Isometric Strength), is performed in a special chair that is fitted with sensors for muscle strength. Once in the chair, the person completes the entire test without position changes, a benefit for those with ALS. In the new study, 100 people with ALS at five sites were examined with ATLIS, along with vital capacity and ALSFRS-R, over the course of at least three visits, to determine how each measure changed over time. The team found that there was less variability in ATLIS than in either of the other two measures, allowing researchers to determine the rate of decline for individual PALS more accurately in less time.
If these results are replicated in a larger study, they suggest that ATLIS could be useful as an outcome measure in ALS clinical trials. ATLIS may be especially useful in smaller trials early in the drug development process, to quickly determine if a new treatment is promising enough to test in a larger trial.
Andres PL, Allred MP, Stephens HE, Proffitt MK, Siener C, Macklin EA, Haines T, English RA, Fetterman KA, Kasarskis EJ, Florence J, Simmons Z, Cudkowicz ME. Fixed Dynamometry is More Sensitive than Vital Capacity or ALS Rating Scale. Muscle Nerve. 2017 Jan 24.