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. 2014 May 20;9(5):e98089.
doi: 10.1371/journal.pone.0098089. eCollection 2014.

A conceptual framework for evaluating impairments in myasthenia gravis

Carolina Barnett  1 , Vera Bril  2 , Moira Kapral  3 , Abhaya Kulkarni  4 , Aileen M Davis  5
Affiliations

A conceptual framework for evaluating impairments in myasthenia gravis

Carolina Barnett et al. PLoS One. .

Abstract

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.

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Conflict of interest statement

Competing Interests: 1. Dr. Barnett holds a clinical research fellowship award by the AAN and American Brain foundation. 2. Dr. Bril has acted as consultant for Grifols, CSL, Bionevia, Lilly, Pfizer, Dainippon Sumitomo, Eisai, and has received research grant support from all of these. 3. Dr. Kapral has no disclosures. 4. Dr. Kulkarni has no disclosures. 5. Dr. Davis has no disclosures. This does not alter the authors' adherence to all the PLOS ONE policies on sharing data and materials.

Figures

Figure 1
Figure 1. Interview Guide.
This is the interview guide used for the interviews. It depicts the open questions and possible probes.
Figure 2
Figure 2. Conceptual Framework for Evaluating Impairments in Myasthenia Gravis.
This diagram depicts our proposed framework of disease severity at the impairment level, in myasthenia gravis patients. The main themes (impairment severity and fatigability) were further sub classified by body region, using the ICF classification.
See this image and copyright information in PMC

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