The prevalence and severity of disease-related disabilities and their impact on quality of life in neuromuscular diseases.

PURPOSE: People with neuromuscular disease experience lower quality of life levels than people from the general population. We examined the prevalence and severity of a broad range of neuromuscular disease-related disabilities and their impact on health-related quality of life. MATERIALS AND METHODS: A cross-sectional postal survey study was conducted among patients diagnosed with neuromuscular disease. Patients completed the Neuromuscular Disease Impact Profile, a disease-related disability impact questionnaire, and two generic health-related quality of life questionnaires: the medical outcome study Short Form Questionnaire and the World Health Organization Quality of Life-bref. The impact of disabilities on quality of life was estimated using multiple regression analyses. RESULTS: Six hundred sixty two patients (68% response rate) completed the questionnaires. There were no differences in quality of life between diagnosis-based subgroups. 'Impairments in muscle functions' had the highest prevalence and severity scores in the total sample and diagnosis-based subgroups. Neuromuscular disease-related disabilities showed strong and independent associations with all aspects of health-related quality of life. 'Impairments in mental functions and pain' was the most important predictor of health-related quality of life followed by 'restrictions in participation in life situations'. CONCLUSIONS: Although 'impairment in muscle functions' is the most prevalent and severe disability, the 'impairments in mental functions and pain' have a strong association with health-related quality of life in patients with a neuromuscular disease. Implications for rehabilitation Disease-related disabilities have a strong and independent associations with all aspects of health-related quality of life. Although health-related domains of quality of life are affected by the neuromuscular disease, the general quality of life is quite good. The most prevalent and severe disability in total group and diagnosis-based subgroups is 'impairments in muscle functions'. The most significant predictor in health-related quality of life is 'impairments in mental functions and pain'.

The extremity function index (EFI), a disability severity measure for neuromuscular diseases: psychometric evaluation.

OBJECTIVE: To adapt and to combine the self-report Upper Extremity Functional Index and Lower Extremity Function Scale, for the assessment of disability severity in patients with a neuromuscular disease and to examine its psychometric properties in order to make it suitable for indicating disease severity in neuromuscular diseases. DESIGN: A cross-sectional postal survey study was performed among patients diagnosed with a neuromuscular disease. METHODS: Patients completed both adapted extremity function scales, questionnaires for psychometric evaluation, and disease-specific questions. Confirmatory factor analysis was performed, and reliability and validity were examined. RESULTS: Response rate was 70% (n = 702). The Extremity Function Index model with a two-factor structure - for upper and lower extremities - showed an acceptable fit. The Extremity Function Index scales showed good internal consistency (alphas: 0.97-0.98). The known-groups validity test confirmed that Extremity Function Index scales discriminate between categories of "Extent of limitations" and "Quality of Life." Convergent and divergent validity tests confirmed that Extremity Function Index scales measure the physical impact of neuromuscular diseases. Relative validity tests showed that the Extremity Function Index scales performed well in discriminating between subgroups of patients with increasing "Extent of limitations" compared to concurrent measurement instruments. CONCLUSION: The Extremity Function Index proved to be a sound and easy to apply self-report disability severity measurement instrument in neuromuscular diseases. Implications for rehabilitation The Extremity Function Index reflects the functioning of all muscles in the upper and lower extremities involved in activities of daily living. The Extremity Function Index is an easy to administer and patient-friendly disability severity measurement instrument that has the ability to evaluate differences in disability severity between relevant neuromuscular disease subgroups. The Extremity Function Index is a valid and reliable disability severity measurement instrument for neuromuscular diseases.

Stability and relative validity of the Neuromuscular Disease Impact Profile (NMDIP).

BACKGROUND: The aim of this study was to examine the stability and relative validity (RV) of the Neuromuscular Disease Impact Profile (NMDIP) using criterion-related groups. In a previous study the NMDIP-scales showed good internal consistency, convergent and discriminant validity. Known-groups analysis showed that the NMDIP discriminates between categories of extent of limitations. METHODS: A cross-sectional postal survey study was performed on patients diagnosed with a NMD and registered at the Department of Neurology, University Medical Center Groningen, the Netherlands. Participants were asked to complete the preliminary NMDIP, the Medical Outcome study Short Form Questionnaire (SF-36), the World Health Organization Quality Of Life-abbreviation version (WHOQOL-bref), and two generic domain specific measures: the Groningen Activity Restriction Scale (GARS) and the Impact on Participation and Autonomy Questionnaire (IPAQ). The variables 'Extent of Limitations' and 'Quality of Life' were used to create criterion-related groups. Stability over time was tested using the Wilcoxon Signed Rank Test for paired samples and the intraclass correlation coefficients for repeated measures. RV was examined by comparing the ability of NMDIP with generic multidimensional health impact measures, and domain specific measures in discriminating between criterion-related subgroups using the Kruskal-Wallis H-test. RESULTS: Response rate was 70% (n = 702). The NMDIP-scales showed sufficient stability over time, and satisfactory or strong RV. In general, the NMDIP scales performed as well as or better than the concurrent measurement instruments. CONCLUSIONS: The NMDIP proved to be a valid and reliable disease-targeted measure with a broad scope on physical, psychological and social functioning.

Development and testing psychometric properties of an ICF-based health measure: The Neuromuscular Disease Impact Profile.

OBJECTIVES: To develop a measure that is based on the International Classification of Functioning, Disability and Health (ICF) and reflects the prevalence and severity of disabilities related to neuromuscular disorders, and to evaluate the psychometric properties of this measure. METHODS: A preliminary questionnaire was developed, based on the categories of the ICF Core Set for Neuromuscular Diseases. Next a cross-sectional postal survey was carried out among 702 patients (70% response rate) diagnosed with a neuromuscular disease. Finally, psychometric properties were examined. RESULTS: The preliminary Neuromuscular Disease Impact Profile (NMDIP) consisted of 45 items. Factor analysis showed that the NMDIP comprised domains representing 3 ICF-components: 5 factors in the Body Functions component, 2 factors in the Activities component, and 1 factor in the Participation component. Scales showed moderate to good internal consistency (α = 0.63-0.92) and mean inter-item correlation coefficients (0.38-0.77). Convergent and discriminant validity analysis indicated that the NMDIP measures the impact of neuromuscular disease on physical, mental, and social functioning. The NMDIP discriminates between groups who differ in extent of limitations. CONCLUSION: The NMDIP is an ICF-based measure that reflects neuromuscular disease-related disabilities. It consists of 36 items divided over 8 scales with satisfactory psychometric properties and 4 single items.

The ambiguity of the concept of participation in measurement instruments: operationalization of participation influences research outcomes.

OBJECTIVE: This study explores, based on the International Classification of Functioning, Disability and Health, the consequences of different operationalizations of participation in regression models predicting participation in one sample of patients. DESIGN: Cross-sectional, comparative study. SETTING: Department of Neurology of a University Hospital. SUBJECTS: A total of 677 patients with a Neuromuscular Disease. MEASURES: Participation was measured using the Neuromuscular Disease Impact Profile questionnaire, the RAND-36 Item Health Survey (social functioning, role limitations-physical, role limitations-emotional) and the Impact on Participation and Autonomy questionnaire (autonomy outdoors, social relations). Potential predictors of participation included type of neuromuscular disease, body functions (measured with Neuromuscular Disease Impact Profile), activities (measured with Neuromuscular Disease Impact Profile), environmental factors (measured with Neuromuscular Disease Impact Profile), and personal factors (measured with the 13-item Sense of Coherence questionnaire). The results were controlled for patient characteristics. RESULTS: Participation was statistically predicted by different determinants depending on the operationalization used for participation. Additionally, the regression coefficients differed significantly. Body functions and activities were predictors in five out of six operationalizations of participation. Sense of coherence predicted participation in all of the operationalizations. The explained variance of the different models ranged from 25% (RAND-36 role limitations-emotional) to 65% (Neuromuscular Disease Impact Profile). CONCLUSIONS: Different operationalizations of participation result in different prediction models. Lack of conceptual consensus makes participation an ambiguous concept in research, and this ambiguity makes evidence-based decisions directed at enhancing participation difficult. Participation needs to be operationalized in an unambiguous and standard way in order to improve the comparability of outcomes.

Experienced stigmatization reduced quality of life of patients with a neuromuscular disease: a cross-sectional study.

OBJECTIVE: To examine the influence of stigma on the quality of life of patients with a neuromuscular disease. DESIGN: Cross-sectional postal survey. SETTING: Outpatient clinic of the Department of Neurology, University Hospital Groningen, the Netherlands. SUBJECTS: Patients diagnosed with a neuromuscular disease. MEASURES: The Stigma Scale for Chronic Illness, the World Health Organization Quality of Life - abbreviated version questionnaires and some background and disease-related questions. The Stigma Scale for Chronic Illness was translated into Dutch according to international guidelines. The impact of stigma on quality of life was estimated using hierarchical multiple regression analysis after controlling for the extent of limitations and patient characteristics. RESULTS: In total 235 patients (75% response rate) were diagnosed with neuromuscular disease and represented all four categories of the approximately 600 neuromuscular diseases. Most patients (86%) reported self stigma, while 64% reported to experience enacted stigma. Experienced quality of life was moderate to good. Stigma contributed to a unique and substantial extent to all domains of quality of life: explained variance for the impact of stigma on quality ranged from 0.13 (social relations) to 0.34 (physical functioning) for self stigma and from 0.09 (social relations) to 0.11 (physical and psychological health, and quality of the environment). CONCLUSION: Self stigma was a stronger predictor for poorer quality of life compared with enacted stigma. In other words: patients suffered more from shame and fear for discrimination (self stigma) than from the really experienced discrimination and exclusion (enacted stigma).