Oropharyngeal dysphagia (OD) can occur in up to 80% of patients with MND and at any time during the course of the disease, regardless of its mode of onset. In patients with bulbar-onset forms, OD appears as one of the initial symptoms, and in spinal-onset forms, it may appear later. Dysphagia is defined as a lack of safety and/or efficacy in swallowing. Both are compromised in MND, which makes dysphagia the main determinant of malnutrition in ALS. In some cases, the first sign of dysphagia is progressive weight loss, but the patient most often reports choking episodes and voice changes after eating. Swallowing safety worsens due to the difficulty to cough and/or clear food remnants that may become stuck in the throat, mainly due to the muscle weakness that characterizes the disease.
An early assessment of the swallowing function is crucial for rapid interventions and slowing down clinical deterioration. Unfortunately, swallowing problems are often underestimated by ALS patients due to their progressive adaptation to the symptoms of bulbar involvement and their denial of the potential progression of the disease. These patients do not always recognize their disorder, which leads to serious consequences, such as malnutrition, dehydration, and reduced survival. Furthermore, dysphagia is underdiagnosed given that many patients present with other cognitive alterations and do not respond to functional assessment processes.
Videofluoroscopy (VFS) is currently the gold-standard technique for evaluating OD regardless of its underlying cause. Even when taking into account its economic and technical cost, VFS is still the technique that allows for best adjusting the nutritional approach to treat patients with this condition. However, due to its high cost, together with its technical requirements, it cannot always be carried out in Functional Motoneuron Disease Units (UFEM, Unidades Funcionales de Enfermedad de Motoneurona).
Although it is true that we have validated, quick, and simple tools that aid in achieving an early detection of OD in other diseases, the clinical evaluation of the dysphagia by means of useful and specific scales or questionnaires in patients with MND is currently insufficient, and further research is needed to develop a specific tool with greater sensitivity and specificity than the existing ones and enabling the screening of OD in patients with this condition. The main purpose of our study was to calculate the specificity and sensitivity of the most frequently used screening questionnaires (Eating Assessment Tool [EAT-10]) and dysphagia stratification scales (ALS Severity Scale [ALS-SS] and Functional Oral Intake Scale [FOIS]) compared with videofluoroscopy in patients with MND. In addition, we also determined the sensitivity and specificity of the quality of life questionnaire for patients with swallowing disorders (SwalQoL-PT), as well as of different subsets of items extracted from this questionnaire (SwalQoL-FS, revised SwalQoL-FS, partial SwalQoL-FS, and SwalQoL-6), even though the SwalQoL-PT is not a dysphagia screening questionnaire used in daily practice or validated for patients with MND.
With regard to the primary objective of this study, we found that, in general, none of the scales has a high sensitivity (or fraction of true positives). Thus, none of the scales proved to be particularly capable of detecting dysphagia. Regarding the validity (sensitivity and specificity) of the scales and tools used for dysphagia screening compared with VFS, the scale yielding the best performance (best Youden index = sensitivity + specificity - 1) was the ALS-SS, and that with the lowest performance was the partial SwalQoL-FS. In contrast, all scales yielded a fairly good specificity (or fraction of true negatives); that is, all of them showed a good ability to detect patients without dysphagia and, in this particular sense, the revised SwalQoL-FS (created based on the section on frequency of dysphagia symptoms named by the patient) was especially relevant.
Taking into account these results, this article describes, for the first time ever, the possibility of using the revised SwalQoL-FS as a screening questionnaire for the diagnosis of dysphagia. In this sense, those patients who obtained a score greater than or equal to 52 in the revised SwalQoL-FS would be patients who do not really have dysphagia and in which case one could safely rule out its involvement. Patients who scored less than 52 in the revised SwalQoL-FS should be re-evaluated for dysphagia symptoms. In this case, the re-evaluation of these patients should be performed on the basis of the ALS-SS.