Translation, cross-cultural adaptation and validation of the Portuguese version of the DYMUS questionnaire for the assessment of dysphagia in multiple sclerosis

Oropharyngeal dysphagia in Multiple Sclerosis (MS) is a relatively common symptom, occurring in 33 - 43% of MS patients (Hartelius & Svensson 1994; Prosiegel et al. 2004; Terré-Bolliart et al. 2004). It can increase significantly with disease progression; impairment in the cerebellar (Poorjavad et al. 2010; De Pauw et al. 2002) and brainstem function systems (De Pauw et al. 2002; Leder et al. 1998). The impact of dysphagia is significant, reducing the quality of life and increasing risk of dehydration and aspiration pneumonia in this population. These complications can be prevented through a rapid screening protocol for the risk of dysphagia in these patients (Poorjavad et al. 2010). In this scenario, the identification of dysphagia symptoms in early stages of MS allows referral to more specific investigations by specialized professional, which includes the use of instrumental deglutition evaluations such as the videofluoroscopy swallowing study (VFSS) and transnasal fibreoptic endoscopic evaluation of swallowing (FEES). Early diagnosis can also make it possible to implement preventive measures, and thus to reduce the risk of complications such as aspiration pneumonia.

To identify the risk of dysphagia in MS, Bergamaschi et al. (2009) developed a simple questionnaire, the DYMUS (Questionnaire for the assessment of Dysphagia in Multiple Sclerosis) (Bergamaschi et al. 2008), validated in 2010 in a large number of patients (Bergamaschi et al. 2009). This instrument is the first questionnaire developed specifically for patients with MS. The DYMUS questionnaire proved to be a useful and consistent instrument to detect oropharyngeal dysphagia and its main features in MS. It can also be used to identify individuals in need of more objective evaluations of swallowing and directing programs for prevention of aspiration. It also showed a very good correlation with swallowing problems and Expanded Disability Status Scales (EDSS) scores. Furthermore, it was associated with a very good internal consistency for both “dysphagia for solid” and “dysphagia for liquid” subscales (Bergamaschi et al. 2008 2009).

The purpose of this study was to translate, cross-culturally adapt and validate to Portuguese the DYMUS questionnaire for the assessment of dysphagia in Multiple Sclerosis.

Construct validity was assessed by using a single-item assessment of perceived dysphagia. Individuals who reported dysphagia in the initial query “Do you have difficulty swallowing?” obtained a significantly higher DYMUS-BR score (median 5, range 1 – 8) compared with those not perceiving dysphagia (median 1, range 1–6), supporting the ability of the questionnaire to discriminate between individuals with and without dysphagia (p<0.001). In addition, Spearman’s correlation coefficients were positive (r_s = 0,357) and show that there was a significant correlation between the both measures (P value= 0.01), suggesting that the two scales were virtually interchangeable in assessing dysphagia.

Until the year 2008, it had not been described in the scientific literature any assessment tool to access the risk of dysphagia specifically in MS patients. Bergamashi and his coworkers (Bergamaschi et al. 2008 2009) developed and validated in a large population (1,734 patients) the DYMUS questionnaire, the subject of this study.

The translation, cross cultural adaptation and validation of questionnaires must be carefully performed. Beaton et al. (1976) emphasized that a poor translation process can result in a non-equivalent to the original instrument. The lack of equivalence can limit the comparison of results obtained in populations separated by their own languages and cultures. In this study, the careful execution of each of these steps aimed the maintenance of the unique properties of the questionnaire, which was reinforced by conducting a pilot study with 40 MS patients and the participation of the experts committee, ensuring content and comprehensibility validity (or face validity) of the Brazilian version of the questionnaire.

In the validation set, more than half (50.6%) of the 85 patients who reported no difficulty in swallowing in the initial question had positive responses to the DYMUS questionnaire and 12.9% of these were classified as having alarming symptoms of dysphagia, pointing to a significant percentage of silent cases, who were identified only by DYMUS. Although we have no knowledge of another published study using the DYMUS questionnaire by way of discussion, we cite the study of Terré-Bolliart et al. (2004) in which, correlating the clinical and VFSS evaluations, found differences in the results obtained by these different forms to assessment of dysphagia, emphasizing the importance of the association of clinical and instrumental methods to evaluate the swallowing process in patients with MS. Also Weisner et al. (2002) studied patients with MS through VFSS, and found swallowing disorders in 75% of patients without clinical signs and symptoms of dysphagia, demonstrating that even patients without symptoms or complaints of dysphagia may have impairments in swallowing. Leder et al. (1998) detected silent aspiration in half of the patients with different neurological degenerative disorders, including multiple sclerosis. These results point to the importance of early identification of MS patients with risk of dysphagia, especially those without clinically evident symptoms of swallowing disorders.

By applying DYMUS-BR, 58% of patients were classified as having some type of swallowing disorder. In the original study developed by Bergamaschi et al. (2008), the prevalence of dysphagia measured by DYMUS was 35%. On the other hand, in the DYMUS validation process (Bergamaschi et al. 2009), 31% of patients had at least one abnormal response on the questionnaire. Using other methods to determine the prevalence of dysphagia in MS patients, Poorjavad et al. (2010) found that 31.7% of the 101 analyzed patients had dysphagia.

The higher values obtained in our study may be attributed to the absence of obvious clinical signs and symptoms of swallowing disorders.

The final version of the DYMUS-BR questionnaire, whose internal consistency was classified as high (Cronbach’s alpha coefficient 0.730), can be considered as reliable, due to the degree of homogeneity of items. The subscales dysphagia for liquids (Cronbach’s alpha coefficient = 0.673) and dysphagia for solids (Cronbach’s alpha coefficient = 0.670) showed satisfactory internal consistencies. In the original validation of the DYMUS, Bergamaschi et al. obtained, the following coefficients: 0.914 (10-item DYMUS questionnaire), 0.885 (dysphagia for solids) and 0.864 (dysphagia for liquids) (Bergamaschi et al. 2009).

In the original version of the DYMUS questionnaire, the question 10 (do you have weight loss?) Was less correlated to other questions, getting still the second lowest frequency of positive responses (8.3%), but even so it has been kept in the questionnaire.in our study, question 10 was also the only one which was not a positive correlation and low correlation coefficient. this can be explained by the fact that in our study, the mean disease duration of MS patients was 8 years old, with a median EDSS of 3, which shows no or mild degree of disability. The association between weight loss and dysphagia is found in the evolutionary course of neurological disorders, being found more often in advanced stages of the disease, where there is greater functional dependency and difficulty swallowing, which may explain the lower scores on question 10.

To our knowledge, there is only one validation study of the DYMUS questionnaire (Bergamaschi et al. 2009).Because of this, by way of comparison, the results obtained were analyzed in the light of other validation studies for the diagnosis of dysphagia. For the construct validity, Dwivedi et al. (2010) have analyzed a cohort of 31 head and neck cancer patients using the correlation coefficient and Mann–Whitney U-test in the validation process of the Sydney Swallow Questionnaire. Both were statistically significant (P <0.01), as in the present study. In the validation process of the Mayo Dysphagia Questionnaire, Grudell et al. (2007) found excellent Spearman rank correlation coefficients values (range of 0.87-0.98). In another study, Chen et al. (2001) developed and validated a dysphagia-specific quality-of-life questionnaire for head and neck cancer patients with Spearman rank correlation coefficients between 0.21 and 0.52. In the current study the coefficient was 0.357, indicating significant positive correlations (P value = 0.01).

The main limitation of our study was that DYMUS is a screening test and like other screening procedures was designed to identify high-risk patients with a specific problem and has been designed to detect signs of dysphagia and its main characteristics in MS patients. Future studies should be focused to analyze correlations between the DYMUS-BR scores and instrumental tools for evaluations of dysphagia such as Videofluoroscopy or FEES. Studies with larger populations are also needed in order to better analyze the types and characteristics of oropharyngeal dysphagia in Brazilian patients with Multiple Sclerosis.

In conclusion, the Brazilian version of the DYMUS questionnaire kept the features originally described, demonstrating to be a reliable, valid, consistent and easy tool to detect the risk of dysphagia in MS patients, that can also be used by healthcare professionals to pre-select patients who could be submitted for more specific instrumental analyses, and to address to programs for prevention of aspiration.

Déborah S Sales - Speech and language Pathologyst, master in neurology, Doctor degree in Neuroloy - Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, RJ, Brazil.

Regina MP Alvarenga – MD, responsible for the Pós Graduate Program in Neurology - Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, RJ, Brazil.

Claudia CF Vasconcelos - MD, Pós Doctor degree Neurology. - Federal University of the State of Rio de Janeiro (UNIRIO), Rio de Janeiro, RJ, Brazil.

Roberta G Silva - Department of Speech and language Pathology, Paulista Estadual University - Marília Campus, São Paulo, Brazil.

Luiz CS Thuler – MD, Coordination of Clinical Research -National Cancer Institute – INCA; Federal University of the State of Rio de Janeiro (UNIRIO) Rio de Janeiro, RJ, Brazil.