1. Introduction

Dysphagia, or difficulty swallowing, may result in acute asphyxia (airway obstruction) ^[1], aspiration pneumonia, dehydration, and malnutrition ^[2]. Dysphagia has been reported in 8.1-80 % of stroke patients, 11-81 % of Parkinson's disease, and 91.7 % of patients with community-acquired pneumonia ^[3]. The prevalence of difficulty swallowing in the community-dwelling elderly may be up to 72% ^[2]. However, dysphagia is often unrecognized because many people are unfamiliar with symptoms and signs of dysphagia (Figure 1) besides choking during swallowing. For nonprofessionals, many of these symptoms and signs are not easily recognized to be associated with dysphagia. Dysphagia screening is therefore important.

Figure 1. Signs and symptoms of dysphagia 

2. Influence and application

A good screening should be a quick process and minimally invasive but can determine the likelihood of dysphagia ^[4]. Here, an algorithm for dysphagia screening is introduced (Figure 2). The algorithm can be used for people unspecialized in dysphagia, e.g., public health practitioners, nurses, or family physicians who have not received the specific training of diagnosing and treating swallowing disorders.

Figure 2. Algorithm for dysphagia screening

This algorithm is a battery of tests applied to screen dysphagia. Each of these tests is simple to learn and use, does not need professional equipment, and does not take much time to perform.

The algorithm includes an initial evaluation of the likelihood of dysphagia including several screening factors  introduced by 0'Neill ^[5] and the Ohkuma Questionnaire ^[6][7][8] (Figure 3), and then several sequential water swallow tests including the Modified water swallow test (3 ml), Kubota water swallowing test (30 ml), and 3-ounce water swallow test (approximate 90 ml) ^[9][10]. Tests with increased volumes of water become more challenging to swallowing ability and therefore are more sensitive. For example, a subject with mild dysphagia may pass the 3 ml water swallow test but fail in the 3-ounce water swallow test.

The most useful factors pointing towards high risks of aspiration include: (1) any disturbance of conscious level; (2) wet voice; (3) weak voluntary cough; (4) cough on drinking small volumes of water; and (5) a timed water swallowing test ^[5].

For each of the water swallowing tests ( 3 ml, 30 ml, and 90 ml), failed to swallow with choking, changes in breathing, presenting post-swallow wet-hoarse voice, holding water in the mouth while drinking, water coming out of the mouth, and throat clearing during or shortly after drinking are positive findings. The 3 ml water swallowing test should be repeated 3 times if the examinee does not demonstrate abnormal signs, and the worst assessment is used as the final result. The 30 ml water swallowing test or 3-ounce water swallow test is performed only once. It is considered abnormal if a subject cannot complete drinking 30 ml water at normal temperature from a cup within 5 s or cannot drink 3-ounce water from a cup without interruption ^[9][10].

Positive findings indicate the necessity for a formal dysphagia evaluation including a flexible endoscopic evaluation of swallowing (FEES) and/or videofluorographic swallowing study (VFSS). FEES and VFSS are considered gold-standard procedures to diagnose dysphagia ^[11].

Figure 3.  Questionnaire for dysphagia screening.