Functional testing.

Functional testing is useful to monitor the natural history of several neuromuscular disorders, and to measure the efficacy of therapeutic agents in clinical trials. A major limitation of functional testing is that a single test is often not appropriate throughout all stages of disease. The same limitation holds true for other measurements of disease progression. MMT and quantitative myometry become technically difficult to perform and lack sensitivity to disease progression at some stages in the course of DMD, ALS, and spinal muscular atrophy. Other limitations of functional testing are its lack of sensitivity to detect a subtle improvement or decline in muscle strength, and the difficulty of applying standard statistical methods to analyze disease progression or therapeutic efficacy. The advantages of functional testing outweigh the limitations. Function testing uses daily activities to monitor disease progression. Patient's appreciate improvements in function more readily than improvements in muscle strength. Functional testing is easily standardized and is reliable. It can be performed, with little or no expense, in almost any clinical setting. The primary challenge for investigators who wish to incorporate functional tests is to identify functional tests that best measure the natural history of the specific disease under investigation. Further, functional testing allows the clinician to provide an educated guess on the likely future course of disease.