Rasch-ionale for neurologists.

Outcome measures are considered the most important tools to monitor patients' outcome in both clinical and research settings. Measuring the clinical state of patients is a fundamental part of our daily clinical practice and research that sometimes is taken for granted. In peripheral neuropathies, there are many scales available, but most of these are at the ordinal level. This paper will systematically address the types of scales available (being nominal, ordinal, interval, or ratio data-based) in terms of their strengths and weaknesses. The differences between classical test theory-based and modern test method-based outcome measures will be addressed with emphasis on Rasch methodology. Various steps will be highlighted as part of the evaluation and construction of outcome measures using the Rasch method, with the aim to increase the knowledge and utility of this technique. We argue that Rasch-built outcome measures should be used for future studies in neuromuscular disorders and their method of construction could be easily extrapolated to other neurological illnesses.

Fatigue and daytime sleepiness scale in myotonic dystrophy type 1.

INTRODUCTION: Fatigue and excessive daytime sleepiness are frequent complaints in myotonic dystrophy type 1 (DM1) that often overlap. We aimed to construct a combined fatigue and daytime sleepiness rating scale for DM1 using the Rasch measurement model. METHODS: Questionnaires, including the Epworth sleepiness scale, fatigue severity scale, and daytime sleepiness scale, were completed by 354 patients. Data were subjected to Rasch analyses and tested for required measurement issues such as appropriate response categories, absence of item bias, local independence, and unidimensionality. RESULTS: The initial 22 items did not meet Rasch model expectations. After rescoring and removing misfitting items, the final 12-item scale showed good model fit and unidimensionality. High internal consistency (person separation index = 0.80) and validity were demonstrated. CONCLUSIONS: The Rasch-built Fatigue and Daytime Sleepiness Scale, developed specifically for DM1 patients, provides interval measures on a single continuum. Its use is suggested for future clinical trials and therapeutic follow-up.

Structural and functional cardiac changes in myotonic dystrophy type 1: a cardiovascular magnetic resonance study.

BACKGROUND: Myotonic dystrophy type 1 (MD1) is a neuromuscular disorder with potential involvement of the heart and increased risk of sudden death. Considering the importance of cardiomyopathy as a predictor of prognosis, we aimed to systematically evaluate and describe structural and functional cardiac alterations in patients with MD1. METHODS: Eighty MD1 patients underwent physical examination, electrocardiography (ECG), echocardiography and cardiovascular magnetic resonance (CMR). Blood samples were taken for determination of NT-proBNP plasma levels and CTG repeat length. RESULTS: Functional and structural abnormalities were detected in 35 patients (44%). Left ventricular systolic dysfunction was found in 20 cases, left ventricular dilatation in 7 patients, and left ventricular hypertrophy in 6 patients. Myocardial fibrosis was seen in 10 patients (12.5%). In general, patients had low left ventricular mass indexes. Right ventricular involvement was uncommon and only seen together with left ventricular abnormalities. Functional or structural cardiac involvement was associated with age (p = 0.04), male gender (p < 0.001) and abnormal ECG (p < 0.001). Disease duration, CTG repeat length, severity of neuromuscular symptoms and NT-proBNP level did not predict the presence of myocardial abnormalities. CONCLUSIONS: CMR can be useful to detect early structural and functional myocardial abnormalities in patients with MD1. Myocardial involvement is strongly associated with conduction abnormalities, but a normal ECG does not exclude myocardial alterations. These findings lend support to the hypothesis that MD1 patients have a complex cardiac phenotype, including both myocardial and conduction system alteration.

Peripheral neuropathy in myotonic dystrophy type 1.

Myotonic dystrophy 1 (DM1) is characterized by a wide range of clinical features. We aimed to verify the presence of peripheral nerve involvement in a large cohort of DM1 patients and to determine clinical consequences. A total of 93 patients underwent detailed neurological examination and nerve conduction studies. Additionally, balance impairment was assessed with the Berg Balance Scale and health status was evaluated with the SF-36 health survey. Sensory symptoms were not reported and mild sensory signs were found in six patients. Electrophysiological abnormalities consistent with a diagnosis of neuropathy were found in 16 patients (17%). Peripheral nerve involvement was significantly associated with decreased muscle strength (p = 0.001) and absence of Achilles-tendon reflexes (p = 0.003), but not with age or duration of neuromuscular symptoms. It had no significant effect on balance, mental or physical health. In conclusion, peripheral nerve involvement may be one of the multisystemic manifestations of DM1, but is usually subclinical. Other causes should be excluded when sensory symptoms or signs are severe.

Reconstructing the Rasch-Built Myotonic Dystrophy Type 1 Activity and Participation Scale.

INTRODUCTION: A previously published Rasch-built activity and participation scale specifically designed for patients with myotonic dystrophy type 1 (DM1) was criticized for having been constructed in a relatively small cohort of patients and containing items too broadly phrased for DM1 patients, thus hampering its clinical use. METHODS: We report the results of the reconstructed Rasch-built DM1 activity and participation scale for clinical use (DM1-ActivC) through Rasch analyses using an expanded questionnaire containing 146 more simply phrased activity and participation inquiries completed by 340 patients with DM1. RESULTS: Through stepwise investigation including data quality control, model fit, response category ordering, local dependency and item bias, we succeeded in reconstructing the DM1-ActivC consisting of 25 items that showed good Rasch model fit, including construct convergent validity, items' weights and persons' locations reliability, and unidimensionality. CONCLUSION: The DM1-ActivC scale has been reconstructed and fulfills all modern clinimetric requirements. Its use is recommended in future longitudinal trials in patients with DM1 to determine its responsiveness.

Rasch-built myotonic dystrophy type 1 activity and participation scale (DM1-Activ).

We describe the development of an outcome measure of activity and participation for patients with myotonic dystrophy type 1 using the Rasch measurement model. A 49-item questionnaire was completed by 163 DM1 patients. Data were subsequently analyzed with Rasch software to design the item set to fit model expectations. Through systematic investigation of response category ordering, model fit, item bias, and local response dependency, we succeeded in constructing a 20-item unidimensional scale of activity and participation (DM1-Activ). High internal consistency (PSI=0.95) and good test-retest reliability values of item difficulty hierarchy and patient location were demonstrated. Patient measures had acceptable correlations with MRC sum scores and MIRS grades (ICC=0.69 and 0.71, respectively), indicating good external construct validity. DM1-Activ is a practical, reliable and valid outcome measure that fulfils all clinimetric requirements. Further evaluation of this scale is needed to provide a nomogram for clinical use.