The Simple Swallowing Provocation Test (SSPT), developed by Teramoto et al. [
11], is a screening test method for detection of aspiration pneumonia, by dripping 0·4 and 2·0 mL of test water via a nasal tube (inner diameter: 0·5 mm) placed in the oropharynx of subjects in the supine position. It is a simple and more widely applicable screening test method for dysphagia, focusing on the presence or absence of induction of the swallowing reflex during the pharyngeal phase, and its sensitivity and specificity to detect the risk of aspiration pneumonia have been reported to be excellent [
16]. However, this test has features that are not suitable for application to the routine assessment of eating/swallowing function by videoendoscopic examination of swallowing in clinical settings, because it requires patients to change their position to the supine position. Therefore, we can challenge developing an altered method for this study, in which an endoscopic probe and a nasal tube are able to be simultaneously inserted using an endoscopic sheath, in order to evaluate both the risk of aspiration pneumonia and possibility of oral feeding. At first, it required us to reconsider the amount of water to be dripped because our study was performed in subjects in a sitting position as same as the normal position for eating. When 0·4 mL of test water was dripped, a significant relationship was observed between LT and the presence of aspiration, while there was no clear relationship when the amount of water was 2·0 mL. The test water was usually deemed to be dripped onto the posterior pharyngeal wall with the method of Teramoto et al. [
11], because the subjects were in the supine position, but in our study, test water was dripped into the vallecula of the larynx because the subjects are in a sitting position. It may be one reason why our LT was prolonged than the previous studies [
17]. In addition, dripping of 2·0 mL of test water into the vallecula of the larynx was observed to be distressing in some patients with poor pharyngeal sensation and to induced the aspiration before swallowing. Therefore, the appropriate amount of test water in this study was considered to be 0·4 mL. Moreover SSPT detect the swallowing reflex on inspection, which means the start of laryngeal elevation. On the other hand our study determined the swallowing reflex as the white-out of endoscopic viewing, which means the top of laryngeal elevation. It may be another reason why our LT was prolonged than the previous studies. When 0·4 mL of test water was used, LT was significantly longer with tube feeding patients and patients than oral intake patients. It may indicate that the swallowing reflex quality may have an important role in the oral intake ability. It is emphasized with our follow-up study that significant relationships between improved FOIS score and LT for evoked swallowing reflex. There are three types of aspiration, including “aspiration before swallowing” which is defined as aspiration before induction of the swallowing reflex or before closing the larynx, “aspiration during swallowing” which occurs due to insufficient laryngeal closure during the period from the start to the end of the swallowing reflex, and “aspiration after swallowing” in which pharyngeal residue falls into the airway after the end of the swallowing reflex [
18]. SSPT was used as an index to estimate whether the speed of the swallowing reflex, considering the timing of swallowing in such patients with poor pharyngeal sensation. Therefore, this test method could provide useful information on the risk of aspiration after swallowing. However, whether the SSPT detects aspiration or penetration before or during swallow correctly is unclear. Recently, Kagaya et al. [
19] determined the sensitivity, specificity, and predictive accuracy of SSPT followed by videofluoroscopic examination of swallowing (VF) and concluded that SSPT has limited applicability as a screening tool for aspiration, silent aspiration, or penetration because of its low sensitivity. It may be the reason that SSPT is designed to detect the risk of saliva aspiration at night however VF as well as FEES is to detect the risk of oral feeding at daytime. Therefore, the most advantage of our developed method was that endoscopic imaging and the concurrent simple endoscopic swallowing test enabled us to observe aspiration and choking on the test water at the same time, which might contribute to prevention of aspiration pneumonia and rehabilitation for oral feeding in dysphagia clinics.