A conceptual framework for evaluating impairments in myasthenia gravis.
BACKGROUND
Myasthenia gravis is characterized by weakness and fatigability of different muscle groups, including ocular, bulbar and the limbs. Therefore, a measure of disease severity at the impairment level in myasthenia needs to reflect all the relevant impairments, as well as their variations with activity and fatigue. We conducted a qualitative study of patients with myasthenia, to explore their experiences and related impairments, aimed at developing a conceptual framework of disease severity at the impairment level in myasthenia gravis.


METHODS
Twenty patients representing the spectrum of disease participated in semi-structured interviews. Interviews were recorded and the transcripts were analyzed by content analysis using an inductive approach with line-by-line open coding. Themes were generated from these codes.


RESULTS
Two main themes were identified: the severity of the impairments and fatigability (i.e., triggering or worsening of an impairment with activity). The impairments were further classified within body regions (ocular, bulbar and axial/limbs). Fatigability was described as a phenomenon affecting the whole body but also affecting specific impairments, and was associated with fluctuation of the symptoms. Patients were concerned that clinical examination at a single point in time might not reflect their true clinical state due to fatigability and fluctuations in severity.


CONCLUSIONS
This conceptual framework reflects the relevance of both severity and fatigability in understanding impairment-based disease severity in myasthenia. This framework could inform the development of impairment measures in myasthenia gravis.
Division of Neurology - Department of Medicine, University of Toronto and University Health Network, Toronto, Canada; Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada.
Carolina
C
Barnett
Division of Neurology - Department of Medicine, University of Toronto and University Health Network, Toronto, Canada.
Vera
V
Bril
Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada; Department of Medicine, University of Toronto and University Health Network, Toronto, Canada.
Moira
M
Kapral
Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada; Department of Neurosurgery, Hospital for Sick Children, Toronto, Canada.
Abhaya
A
Kulkarni
Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada; Division of Health Care and Outcomes Research, Toronto Western Research Institute, University Health Network, Toronto, Canada; Department of Physical Therapy and Graduate Department of Rehabilitation Science, University of Toronto, Toronto, Canada.
Aileen M
AM
Davis
D000328:Adult; D000368:Aged; D000465:Algorithms; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000175:diagnosis*; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires