History of outcome measures for myasthenia gravis

Psychometric properties of MG-ADL items and MG-ADL score: An assessment of distributional characteristics, validity and factor structure in two large datasets

BACKGROUND

The Myasthenia Gravis-Activities of Daily Living scale (MG-ADL) is an 8-item outcome measure to assess symptoms and functional limitations in myasthenia gravis (MG) patients. The MG-ADL score is an equally weighted level sum score that is used as primary outcome measures in clinical trials, in clinical practice, and as an end-point in health economic evaluation. This data analysis aims to obtain detailed knowledge of measurement properties of MG-ADL items and the MG-ADL score.

METHODS

Cross-sectional data from a real-world prospective study (MRW) were combined with longitudinal data from the ADAPT trial. Outcome measures included were MG-ADL, Quantitative Myasthenia Gravis score (QMG), MG 15-item Quality of Life (MG-QOL15r) and EQ-5D-5L. Patients were categorized by their Myasthenia Gravis Foundation of America (MGFA) clinical classification. The following measurement properties were assessed: distributional characteristics, inter-item correlation, convergent, known groups and construct validity and internal factor structure.

RESULTS

Correlations of items within MG-ADL dimensions were moderate, while MG-ADL correlations between comparable MG-QOL15r and QMG items were mixed. Known groups validity for the MG-ADL score was demonstrated for MGFA class. Mean MG-ADL item level scores by MGFA class demonstrated construct validity. PCA, including all four outcome measures, resulted in a nine factor solution.

DISCUSSION

Psychometric properties of individual MG-ADL items were moderate to good. This study showed that the MG-ADL adequately captures the multidimensional heterogeneous nature of MG. This is, however, accompanied by mixed psychometric performance of the MG-ADL score, which may complicate health economic modelling.

REGISTRATION

MyRealWorld-MG was registered on November 25, 2019, with registration numberNCT04176211. The ADAPT randomized clinical trial is registered atClinicalTrials.gov(NCT03669588).

Impact of Ravulizumab on Patient Outcomes and Quality of Life in Generalized Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune ion channel disorder in which antibodies to different end-plate antigens impair neuromuscular transmission, ultimately leading to muscle weakness and fatigability. In about 85% of patients with MG, autoantibodies against the acetylcholine receptor (AChR) activate the complement cascade, causing damage to the neuromuscular junction. MG is a chronic disorder for which standard therapies with corticosteroids, immunosuppressive drugs, and immunomodulation with plasma exchange or intravenous immunoglobulins modify the course of the disease, but the residual burden of physical, psychological, and social disability highlights several unmet needs, among these the need for specific, targeted, and well tolerated therapies able to improve the patients' quality of life. Complement inhibition paved the way to precision medicine in MG since, for the first time, a specific therapy targeting a crucial pathogenetic step has been designed, tested, and proven to be effective in a controlled fashion. Ravulizumab represents the first long-acting complement inhibitor approved for treatment of patients with generalized MG, able to provide rapid, complete, and sustained complement inhibition. Ravulizumab improved the MG Activity of Daily Living scale and other clinical parameters up to 26 weeks as shown by the CHAMPION MG trial, and by its open label extension, with the added value of being administered every 8 weeks. The schedule of administration is likely to improve patients' adherence and hence their quality of life. The introduction of complement inhibition will considerably change the traditional therapeutic strategy for MG.

Female sex and overweight are associated with a lower quality of life in patients with myasthenia gravis: a single center cohort study

BACKGROUND

Myasthenia gravis (MG) affects individuals as a chronic autoimmune disease for many years. Commonly, chronic diseases significantly reduce the patients' quality of life. Aiming to improve the future quality of life in MG, this study assessed the factors impacting quality of life. As gender-specific medicine is becoming increasingly important, this study also focused on understanding gender differences in the outcome of MG.

METHODS

The study is a combined monocentric, retrospective and prospective database analysis of patient records based on 2,370 presentations of 165 patients with clinically, serologically and/or electrophysiologically confirmed MG over an observation period of up to 47 years. The data collection included the following parameters: antibody status, disease severity, age, medication use, gender, and disease duration. In addition, a prospective survey was conducted on the quality of life using the Myasthenia gravis-specific 15-item Quality of Life scale (MG-QoL15) and on the activities of daily living using the MG-specific Activities of Daily Living scale (MG-ADL).

RESULTS

Of the 165 patients, 85 were male (51.5%) and 80 were female (48.5%). The remaining baseline characteristics (e.g. age and antibody status) were consistent with other myasthenia gravis cohorts. A high body mass index (BMI) (p = 0.005) and a high disease severity (p < 0.001) were significantly associated with lower disease-specific quality of life. Additionally, the quality of life in women with MG was significantly reduced compared to male patients (19.7 vs. 13.0 points in the MG-QoL15, p = 0.024). Gender differences were also observable in terms of the period between initial manifestation and initial diagnosis and women were significantly more impaired in their activities of daily living (MG-ADL) than men (4.8 vs. 3.0 points, p = 0.032).

CONCLUSION

Women with MG had significantly poorer disease specific quality of life compared to men as well as patients with a higher BMI. In order to improve the quality of life, gender-specific medicine and further investigation regarding a modification of the quality of life by lowering the BMI are essential and necessary.

TRIAL REGISTRATION

Study approval by the Ethics Committee of the University Medical Center Göttingen was granted (number 6/5/18).

Novel DPAGT1 Gene Mutation in Two Twins with Congenital Myasthenic Syndrome and a Review of the Literature

Congenital myasthenic syndromes (CMS) are rare diseases caused by mutation in genes coding for proteins involved in neuromuscular junction structure and function. DPAGT1 gene mutations are a rare cause of CMS whose clinical evolution and pathophysiological mechanisms have not been clarified completely. We present the case of two twins displaying an infancy-onset predominant limb-girdle phenotype and carrying a novel DPAGT1 mutation associated with unusual histological and clinical findings. CMS can mimic paediatric and adult limb-girdle phenotype, hence neurophysiology plays a fundamental role in the differential diagnosis.

Towards Personalized Medicine in Myasthenia Gravis: Role of Circulating microRNAs miR-30e-5p, miR-150-5p and miR-21-5p

Myasthenia gravis (MG) is an autoimmune neuromuscular disease characterized by fatigable skeletal muscle weakness with a fluctuating unpredictable course. One main concern in MG is the lack of objective biomarkers to guide individualized treatment decisions. Specific circulating serum microRNAs (miRNAs) miR-30e-5p, miR-150-5p and miR-21-5p levels have been shown to correlate with clinical course in specific MG patient subgroups. The aim of our study was to better characterize these miRNAs, regardless of the MG subgroup, at an early stage from diagnosis and determine their sensitivity and specificity for MG diagnosis, as well as their predictive power for disease relapse. Serum levels of these miRNAs in 27 newly diagnosed MG patients were compared with 245 healthy individuals and 20 patients with non-MG neuroimmune diseases. Levels of miR-30e-5p and miR-150-5p significantly differed between MG patients and healthy controls; however, no difference was seen compared with patients affected by other neuroimmune diseases. High levels of miR-30e-5p predicted MG relapse (p = 0.049) with a hazard ratio of 2.81. In summary, miR-150-5p is highly sensitive but has low specificity for MG, while miR-30e-5p has the greatest potential as a predictive biomarker for the disease course in MG, regardless of subgroup.

Utilization of MG-ADL in myasthenia gravis clinical research and care

The Myasthenia Gravis Activities of Living (MG‐ADL) scale is an 8‐item patient‐reported scale that measures myasthenia gravis (MG) symptoms and functional status. The objective of the current review is to summarize the psychometric properties of the MG‐ADL and published evidence of MG‐ADL use. A targeted literature review for published studies of the MG‐ADL was conducted using a database and gray literature search. A total of 48 publications and 35 clinical trials were included. Studies indicated that the MG‐ADL is a reliable and valid measure that has been used as an outcome in clinical trials and observational studies to measure MG symptoms and response to treatment. While most often used as a secondary endpoint in clinical trials, its use as a primary endpoint has increased in recent years. The most common MG‐ADL endpoint is change in MG‐ADL score from baseline, although there has been an increase in the analysis of a responder threshold using the MG‐ADL. A new concept of minimal symptom expression (MSE) has emerged more recently. Duration of treatment effect is another important construct that is being increasingly evaluated using the MG‐ADL. The use of the MG‐ADL as a primary endpoint in clinical trials and in responder threshold analyses to indicate treatment improvement has increased in recent years. MSE using the MG‐ADL shows promise in helping to determine success of treatment and may be the aspirational goal of MG treatment for the future once validated, particularly given the evolving treatment landscape in MG.

Validation of Spanish version of 15-item myasthenia gravis quality-of-life questionnaire

OBJECTIVES

The aim of this study was to achieve the translation and cross-cultural adaptation of the MG-QOL15R questionnaire into Spanish and the analysis of its psychometric properties.

MATERIALS AND METHODS

We recruited patients with MG, ≥18 years old, whose mother tongue was Spanish. After the translation and cross-cultural adaptation of the MG-QOL15-R, the following tests were performed: internal consistency using the Cronbach-α coefficient and corrected item-total correlations; reproducibility with a test-retest analysis using intraclass correlation coefficients; and concurrent validity using Spearman's correlation coefficient of the Spanish language MG-QOL15R-S, Myasthenia Gravis Activity of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores. As an approximation to construct validity, the nonparametric Mann-Whitney U test was performed between MG-QOL15R-S scores according to the Myasthenia Gravis Foundation of America classification.

RESULTS

A total of 83 MG patients were enrolled, mean age 48.19 ± 17.25 years; 58 (69.9%) were women. The mean MG-QOL15R-S score was 11.3 ± 7.1. Cronbach-α coefficient was 0.92. Item-total correlation ranged between 0.43 and 0.75. Intraclass correlation coefficient was 0.80. The Spearman correlation coefficient was 0.637 (p-value < .001) for MG-ADL and 0.487 (p-value < .001) for QMG. Mann-Whitney U tests of the mean MG-QOL15R-S scores were significantly different according to the clinical severity (p-value < .001).

CONCLUSIONS

The Spanish version of the MG-QOL15R is a valid and reliable instrument and potentially useful for measuring health-related quality of life in Spanish-speaking MG patients.

Outcome Measures in Clinical Trials of Patients With Myasthenia Gravis

Myasthenia gravis (MG) is a heterogeneous disorder whose clinical presentation ranges from mild ocular deficits to severe widespread weakness. This variance poses a challenge when quantifying clinical deficits. Deficits and symptoms are quantified using standardized clinical scales and questionnaires which are often used as outcome measures. The past decades have seen the development of several validated outcome measures in MG, which are used in clinical trials to obtain regulatory approval. In recent years, emphasis has moved from objective assessments to patient-reported outcomes. Despite a growing body of literature on the validity of the MG-specific outcome measures, several unresolved factors remain. As several novel therapeutics are currently in clinical development, knowledge about capabilities and limitations of outcome measures is needed. In the present paper, we describe the most widely used clinical classifications and scales in MG. We highlight the choice of outcome measures in published and ongoing trials, and we denote whether trial efficacy was reached on these outcomes. We discuss advantages and limitations of the individual scales, and discuss some of the unresolved factors relating to outcome assessments in MG.

Update in immunosuppressive therapy of myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disease of the neuromuscular junction. Immunosuppressive treatments are part of the therapeutic armamentarium in MG. Long-term systemic steroid administration carry considerable risks and adverse events. Consequently, steroid-free immunosuppressive therapy is necessary to reduce the dose or discontinue steroids. First immunosuppressive drug trials in MG were performed in the mid-60s using standard and nonspecific immunosuppression. Since then, only few randomized controlled clinical trials were conducted in MG and assesed drug efficacy in terms of its steroid-sparing capacity and the ability to reduce myasthenic signs and symptoms. Treatment strategy in MG is quite challenging, mainly due to the disease heterogeneity in terms of clinical presentation, immunopathogenesis and drug response. To solve this dilemma, emerging treatment are based on biological drugs and use new targets of the immune pathway.

History of Myasthenia Gravis Revisited

The first description of myasthenia gravis (MG) was given by Thomas Willis in 1672. MG was the focus of attention after mid-nineteenth century and a great amount of information has been accumulated in a span of 150 years. The aim of this review is to convey this information according to a particular systematic and to briefly relate the experience of Istanbul University. MG history was examined in four periods: 1868-1930, 1930-1960, 1960-1990, and 1990-2020. In the first period (1868-1930), all the clinical characteristics of MG were defined. Physiological/pharmacological studies on the transmission at the neuromuscular junction were initiated, and the concept of repetitive nerve stimulation emerged. A toxic agent was believed to be the cause of MG which appeared to resemble curare intoxication. Association of MG with thymus was noticed. No noteworthy progress was made in its treatment. In the second period (1930-1960), acetylcholine was discovered to be the transmitter at the neuromuscular junction. Repetitive nerve stimulation was used as a diagnostic test. The autoimmune nature of MG was suspected and experiments to this end started to give results. The hallmark of this period was the use of anticholinesterases and thymectomy in the treatment of MG. The third period (1960-1990) can probably be considered a revolutionary era for MG. Important immunological mechanisms (acetylcholine receptor isolation, discovery of anti-acetylcholine receptor antibodies) were clarified and the autoimmune nature of MG was demonstrated. Treatment modalities which completely changed the prognosis of MG, including positive pressure mechanic ventilation and corticosteroids as well as plasma exchange/IVIg and azathioprine, were put to use. In the fourth period (1990-2020), more immunological progress, including the discovery of anti-MuSK antibodies, was achieved. Videothoracoscopic thymectomy reduced the morbidity and mortality rate associated with surgery. New drugs emerged and clinical trials were performed. Valuable guidelines were published. In the last part of the review, the experience in MG of Istanbul University, a pioneer in Turkey, is related.

Gender and quality of life in myasthenia gravis patients from the myasthenia gravis foundation of America registry

INTRODUCTION

Quality of life (QOL) has been poorly characterized among patients with myasthenia gravis (MG) other than assessments performed within the clinical setting.

METHODS

Patients age ≥ 18 years who were diagnosed with MG and registered with the MG patient registry between July 1, 2013, and June 30, 2016, were included. Demographic information, disease related history, and QOL were compared between men and women using multivariable analysis.

RESULTS

A total of 1,315 subjects (827 women) were included. Women were significantly younger, had a younger age at symptom onset, and were more likely to have thymoma and thymectomy. The 15-item Myasthenia Gravis Quality of Life scale (MG-QOL15) was significantly worse in women. MG-QOL15 score was comparable between women who had thymectomy and men with or without thymectomy.

DISCUSSION

QOL among MG patients is worse in women compared with men, but this disparity is eliminated in women who have undergone thymectomy. Muscle Nerve, 2018.

Validity, reliability, and sensitivity to change of the myasthenia gravis activities of daily living profile in a sample of Italian myasthenic patients

The purpose of this study is to report on the validity, reliability, and sensitivity of the myasthenia gravis activities of daily living profile (MG-ADL) in a sample of Italian patients. Patients with myasthenia gravis (MG) completed a protocol that included the MG-ADL, the WHO Disability Assessment Schedule (WHODAS 2.0), the Besta Neurological Institute rating scale for myasthenia gravis, and the MG-composite. Cronbach's alpha was used to test reliability, Spearman's correlation and intra-class correlation coefficient (ICC) to test short-term test-retest, Kruskal-Wallis test to assess differences in MG-ADL between patients with different disease severity, and Wilcoxon signed-rank test to assess sensitivity to change. In total, 58 patients were enrolled: 44 were females, mean MG duration 10.5 ± 10.4 years, mean MG-ADL 3.98 ± 3.07. The MG-ADL showed good internal consistency (alpha = .774), stability (test-retest correlation = .98, ICC = .97). It was superior to the WHODAS 2.0 in differentiating patients with different MG type and severity (P < .001), it showed higher sensitivity to change (P = .001 for improved and P = .007 for worsened patients) and higher correlation with the MG-composite (RHO = .625). Our analysis shows that the Italian version of the MG-ADL is valid, reliable, stable, and sensitive to change.

Social disadvantages associated with myasthenia gravis and its treatment: a multicentre cross-sectional study

OBJECTIVES

To clarify the social disadvantages associated with myasthenia gravis (MG) and examine associations with its disease and treatment.

DESIGN

Cross-sectional study.

SETTING AND PARTICIPANTS

We evaluated 917 consecutive cases of established MG seen at 13 neurological centres in Japan over a short duration.

OUTCOME MEASURES

All patients completed a questionnaire on social disadvantages resulting from MG and its treatment and a 15-item MG-specific quality of life scale at study entry. Clinical severity at the worst condition was graded according to the MG Foundation of America classification, and that at the current condition was determined according to the quantitative MG score and MG composite. Maximum dose and duration of dose ≥20 mg/day of oral prednisolone during the disease course were obtained from the patients' medical records. Achievement of the treatment target (minimal manifestation status with prednisolone at ≤5 mg/day) was determined at 1, 2 and 4 years after starting treatment and at study entry.

RESULTS

We found that 27.2% of the patients had experienced unemployment, 4.1% had been unwillingly transferred and 35.9% had experienced a decrease in income, 47.1% of whom reported that the decrease was ≥50% of their previous total income. In addition, 49.0% of the patients reported feeling reduced social positivity. Factors promoting social disadvantages were severity of illness, dose and duration of prednisolone, long-term treatment, and a depressive state and change in appearance after treatment with oral steroids. Early achievement of the treatment target was a major inhibiting factor.

CONCLUSIONS

Patients with MG often experience unemployment, unwilling job transfers and a decrease in income. In addition, many patients report feeling reduced social positivity. To inhibit the social disadvantages associated with MG and its treatment, greater focus needs to be placed on helping patients with MG resume a normal lifestyle as soon as possible by achieving the treatment target.

Determinants of quality of life in Brazilian patients with myasthenia gravis

OBJECTIVES

The aims of the current study were 1) to evaluate the reliability and validity of the Brazilian version of the 15-item Myasthenia Gravis Quality of Life Scale and 2) to investigate the quality of life of Brazilian patients with myasthenia gravis and its determinants.

METHODS

This cross-sectional study included 69 patients with myasthenia gravis who underwent neurological evaluation and completed questionnaires regarding quality of life (the 36-item Short Form of the Medical Outcomes Study and the 15-item Myasthenia Gravis Quality of Life Scale), anxiety and depressive symptoms.

RESULTS

The Brazilian version of the 15-item Myasthenia Gravis Quality of Life Scale showed high internal consistency and good concurrent validity with the 36-item Short Form of the Medical Outcomes Study and its subscales. Determinants of quality of life in Brazilian patients with myasthenia gravis included the current status of myasthenia gravis as assessed by the Myasthenia Gravis Composite, the current prednisone dose and the levels of anxiety and depression.

CONCLUSION

The Brazilian version of the 15-item Myasthenia Gravis Quality of Life Scale is a valid instrument. Symptom severity, prednisone dosage and anxiety and depression levels impact the quality of life of patients with myasthenia gravis.

Validation of the Besta Neurological Institute rating scale for myasthenia gravis

INTRODUCTION

We validated the scale for myasthenia gravis (MG) developed at the Neurological Institute Foundation of Milan (INCB-MG scale).

METHODS

A total of 174 patients were evaluated with the INCB-MG and compared with the MG Composite (MGC) as the gold standard. Dimensionality, reliability, and validity of the INCB-MG scale were studied by principal component factor analysis, Cronbach alpha, and Pearson correlation coefficients; interobserver reliability was calculated by the weighted Cohen K coefficient.

RESULTS

Generalized and bulbar INCB-MG subscales were unidimensional with excellent consistency; the INCB-MG and MGC scales were strongly correlated. Fatigability assessment was correlated with the INCB-MG generalized, bulbar, and respiratory subscales.

CONCLUSIONS

The INCB-MG scale is a reliable tool to assess MG and is strongly correlated with the MGC. The INCB-MG scale is a valid tool for every day practice and should be further investigated for its application in clinical trials.

PTPN22 R620W Polymorphism is Associated with Myasthenia Gravis Risk: A Systematic Review and Meta-Analysis

Backround

The association between PTPN22 R620W polymorphism and risk of myasthenia gravis (MG) remains controversial. Therefore, we did this meta-analysis to investigate this association.

Material/Methods

We did a comprehensive search in PubMed, Medline, Embase, CNKI (China National Knowledge Infrastructure), and Wanfang electronic databases to retrieve relevant articles. The overall effect was measured by odds ratios (ORs) with its 95% confidence intervals (CIs). Statistical analyses were conducted with STATA software.

Results

Overall, a total of 7 case-control studies with 2802 cases and 3730 controls were finally included in this review. PTPN22 R620W polymorphism was significantly associated with an increased risk of MG (OR=1.57; 95% CI, 1.34–1.82; I²=31%). In the subgroup analysis, thymoma patients were significantly associated with risk of MG (OR=1.59; 95% CI, 1.28–1.98; I²=0%). However, non-thymoma patients with this polymorphism did not have increased MG risk (OR=1.36; 95% CI, 0.86–2.15; I²=77%). In addition, PTPN22 R620W polymorphism showed increased early-onset myasthenia gravis (EOMG) risk (OR=2.38; 95% CI, 1.52–3.71; I²=0%).

Conclusions

This meta-analysis shows a significant association between PTPN22 R620W polymorphism and MG risk.

Diurnal and day-to-day variation of isometric muscle strength in myasthenia gravis

INTRODUCTION

In patients with myasthenia gravis (MG), muscle strength is expected to decrease gradually during the day due to physical activities.

METHODS

Isometric muscle strength at the shoulder, knee, and ankle was determined in 10 MG patients (MGFA class II-IV) who were receiving usual medical treatment and in 10 control subjects. To determine diurnal and day-to-day variation, muscle strength was measured 4 times during day 1 and once at day 2.

RESULTS

Knee extension strength decreased during the day in both patients and controls. Neither diurnal nor day-to-day variation of muscle strength was higher in patients compared with controls.

CONCLUSIONS

Patients with mild to moderate MG did not have increased variation of isometric muscle strength during the day or from day-to-day compared with controls. This suggests that isometric muscle performance can be determined with high reproducibility in similar groups of MG patients without regard to time of day.

The clinical absolute and relative scoring system-a quantitative scale measuring myasthenia gravis severity and outcome used in the traditional Chinese medicine

Myasthenia gravis (MG) is a chronic autoimmune disease caused by autoantigen against the nicotine acetylcholine receptor at the neuromuscular junction. With modern treatment facilities, the treatment effect and outcome for MG has been greatly improved with MG and non-MG patients enjoying the same life expectancy. Many classifications of disease distribution and severity have been set up and tested all over the world, mainly in the western world. However, the absolute and relative scoring system for evaluating the severity and treatment effect of MG in China where traditional Chinese medicine (TCM) has been practiced for thousands of years has not been introduced worldwide. The TCM has achieved a great success in the treatment of MG in the country with a huge population. This article serves to introduce this scoring system to the world.

Preoperative high-dose steroid has long-term beneficial effects for myasthenia gravis

Previous studies addressing preoperative steroid treatment have revealed that control of myasthenia gravis (MG) with steroids prior to surgery appeared to stabilize postoperative status. The purpose of our study was to clarify the clinical benefits of the preoperative programmed high-dose steroid treatment on the long-term outcomes of MG patients. We retrospectively reviewed the records of 171 MG patients who were followed up after undergoing thymectomy in our hospital between 1988 and 2006. One hundred and thirteen patients in the programmed treatment group had received preoperative steroid treatment, while 58 patients received no steroid treatment during the preoperative period. Clinical remission, which was defined as the achievement of the modified pharmacologic remission (PR) for at least 1 year, and clinical benefits were compared between the two groups. With regard to the remission after thymectomy, Kaplan-Meier life-table curves for patients in the preoperative steroid treatment group versus those for patients in the no steroid preoperative treatment group revealed a significantly higher probability of the PR in the preoperative steroid treatment group (log-rank test, P < 0.01). This study might be the first, as per our knowledge, to indicate that preoperative programmed high-dose steroid treatment has long-term beneficial effects for MG patients.

Development of the MG-DIS: an ICF-based disability assessment instrument for myasthenia gravis

PURPOSE

To develop a preliminary version of a disease-specific, patient-reported disability assessment instrument for myasthenia gravis (MG) based on the International Classification of Functioning, Disability and Health (ICF): the MG-DIS.

METHODS

Five consecutive steps were taken: literature review and selection of outcome measures; linking of measures' concepts to ICF categories and selection of those reported by 30% of the instruments; comparison of linking results with a previous selection of MG-relevant ICF categories; patient interview; development of questions based on retained ICF categories.

RESULTS

Thirty-one papers containing 21 different outcome measures were found: 13 ICF categories were linked to them. Fifty-five items were retained after the comparison with the list of MG-specific categories, and were used for patient interview. Thirteen interviews were conducted before saturation of data was reached and the final list was composed of 42 categories: based upon them, 44 questions were developed.

CONCLUSIONS

The preliminary version of the MG-DIS contains more information than each single MG-specific tool, in particular, for the component of environmental factors. Further research is needed to test its psychometric properties.

IMPLICATIONS FOR REHABILITATION

It is important that patient-reported outcome is incorporated in MG patient's assessment. MG features can be evaluated with ICF-based methods. An MG-specific patient-reported disability assessment instrument can be used to monitor changes of functioning in patients on MG-specific treatments, and can be used in clinical trials as outcome measure.

The MG composite: an outcome measure for myasthenia gravis for use in clinical trials and everyday practice

The myasthenia gravis composite (MGC) was constructed by selecting the best performing items from three commonly used, MG-specific scales. The response categories of the items were subsequently weighted for importance. The MGC, which takes less than five minutes to complete, is made up of three ocular, three bulbar, one respiratory, one neck, and two limb items. After its construction, the MGC was validated in an 11-center scale validity study. During the validation study, which included test-retest analysis, it was determined that a 3-point improvement in MGC score reliably indicates clinical improvement. A 3-point improvement in MGC also appears to be meaningful to the patient. Rasch analysis of the MGC confirmed that all 10 items belong and can be summed to provide a total score, and that the weights given to the response categories of the items are appropriate.