The Swallowing Disturbance Questionnaire (SDQ) is a widely used tool for screening dysphagia in patients with Parkinson’s disease (PD) [1]. Dysphagia, or swallowing difficulty, is a frequent problem in PD that can lead to serious consequences, such as malnutrition and aspiration pneumonia [2]. The SDQ is a quick and easy method for identifying patients at risk for dysphagia and referring them for further evaluation and treatment. It can be completed in just a few minutes, and no special skills or equipment are needed. This makes it easy to use in many different settings, including hospitals, nursing homes, and outpatient clinics.

The SDQ is a self-report questionnaire comprising 15 items that assess various aspects of swallowing function, including the ability to chew and swallow different types of food and liquids, the presence of coughing or choking during meals, and difficulty in breathing. Each item is scored on a 4-point scale, with higher scores indicating more frequent symptom experience, except the last question about the history of respiratory infection (yes/no).

The SDQ was originally developed and validated in 57 patients with PD in 2007 [1]. The Cronbach’s alpha coefficient was reported as being 0.89. The presence of dysphagia was defined as any abnormal finding in clinical examination by dysphagia specialists or penetration/aspiration in the fiberoptic endoscopic evaluation of swallowing (FEES). The optimal cutoff value for detecting dysphagia was 11, with sensitivity of 80.5% and specificity of 81.3%.

The SDQ has been translated and adapted into several other languages, including Japanese, Persian, Korean, and Portuguese (Table 1). The Japanese version demonstrated Cronbach’s alpha coefficient of 0.84, sensitivity of 77.8%, and specificity of 84.6% to detect patients with aspiration in the videofluoroscopic swallowing study (VFSS) [3]. In the Persian version, Cronbach’s alpha coefficient was reported as 0.86, and sensitivity and specificity were 96.7% and 91.2%, respectively, for detecting aspiration during VFSS [4]. In the Korean version, Cronbach’s alpha coefficient was 0.85, and sensitivity and specificity were 72.7% and 96.2%, respectively, for detecting aspiration during VFSS [5]. In the Portuguese version, Cronbach’s alpha was 0.95, and an area under the receiver operating characteristics curve was 0.70 for detecting chewing and swallowing problems on the Movement Disorder Society-Unified Parkinson’s Disease Rating Scale item 2.3, without reporting sensitivity and specificity [6].

The SDQ has also been applied as a dysphagia screening test for diseases other than PD. When applied to patients with dysphagia caused by various conditions, including neurologic disorders, head and neck tumors, and gastrointestinal diseases, it showed a sensitivity of 79.7% and a specificity of 73% for the detection of oromotor abnormalities on physical examination and pharyngeal abnormalities on FEES [7]. Although the accuracy was lower than PD, it suggests that the SDQ can be used as a screening tool for dysphagia caused by various diseases. Recently, the usefulness of the SDQ was evaluated in patients with multiple system atrophy (MSA), one of the atypical parkinsonism [8]. However, the sensitivity to detect dysphagia confirmed by FEES was only 54%. The authors constructed the MSA-SDQ subscore by extracting five items highly correlated with dysphagia in MSA patients. When the subscore was used, Cronbach’s alpha coefficient was 0.81, and sensitivity of 85% and specificity of 100% were reported. However, further studies will be needed to validate the MSA-SDQ subscore because of the small sample size and lack of validation in an independent patient population. Recent evidence has further expanded the clinical utility of the SDQ as a valid screening tool for swallowing impairments and aspiration risk in patients with multiple sclerosis [9,10].

In conclusion, the SDQ is a valuable tool for screening dysphagia in patients with PD. Its simplicity and effectiveness make it an important tool for identifying patients at risk for dysphagia and referring them for further evaluation and treatment. Its high internal consistency, sensitivity, and specificity, as well as its availability in multiple languages, make it a reliable and widely applicable indicator of dysphagia in this population. Additional research will be needed for application to other disease groups.