MG-ADL, a patient-reported scale commonly used to address symptom severity in myasthenia gravis (MG), has a poor sensitivity for measuring generalized muscle weakness. Researchers suggest that more questions about it be added.
The study, titled “Sensitivity of MG–ADL for generalized weakness in myasthenia gravis,” was published in the journal European Journal of Neurology.
MG‐ADL (Myasthenia Gravis Activities of Daily Living) is a patient-reported, eight-question survey that provides a rapid and easy-to-apply assessment of MG symptom severity.
The survey has commonly been used in clinical trials to measure treatment outcomes over activities of daily living and correlates well with the Quantitative MG (QMG), a reliable physician-reported scale often used in clinical studies.
Overall there is a good match between both scores, but there have been inconsistencies when using one versus the other to measure the effect of treatments on muscle weakness.
One explanation may be that MG-ADL has only three questions asking about general weakness, while QMG contains more items focusing on that symptom. This raises the question of whether MG-ADL is equally sensitive to changes in patient muscle weakness, researchers said.
The team, working at the Leiden University Medical Center in the Netherlands, reasoned that adding more questions on weakness would improve MG-ADL’s accuracy and approximate the test’s sensibility to that of QMG.
To investigate that, researchers first evaluated the correlation between both scores in terms of ocular (oculobulbar) and generalized weakness, then tested whether adding questions asking patients about muscle weakness would increase such a correlation.
The study included a group of 112 MG patients, whose symptoms were evaluated using the two scoring systems.
The results showed that MG‐ADL had a higher correlation with the QMG domain of ocular weakness than with the QMG items addressing generalized weakness, demonstrating that MG‐ADL was a poorer test to measure general weakness.
But ACTIVLIM, a previously validated, patient-reported survey specific to general muscle weakness, significantly compensated for this mismatch between MG-ADL and QMG, meaning that
adding questions on general weakness would improve the sensitivity of MG–ADL to evaluate those symptoms, “thereby increasing the overall performance” of the test
in future clinical trials, researchers said.
The added value of ACTIVLIM was seen for the overall group scores and for changes in individual patients.
“Importantly, we do not propose using ACTIVLIM as a primary outcome measure in MG as it lacks oculobulbar items,” researchers stated. It may, however, be used together with MG-ADL for future outcome measures.
As QMG and MG–ADL are likely to remain the leading outcome measures, researchers also suggested reporting the oculobulbar and generalized subscores separately.