The Repetitive Saliva Swallowing Test (RSST): Procedure, Cut-offs and Clinical Evidence

The Repetitive Saliva Swallowing Test (RSST) is a simple, bedside swallowing screening test that requires no equipment beyond a timer, no food or liquid bolus, and no specialist training. Developed in Japan by Oguchi and Saitoh in 1996, it has been widely adopted across Asia — including in Hong Kong — as a first-line dysphagia screening tool, particularly in acute care and residential care settings.

This article follows ASHA Practice Portal guidance on adult dysphagia and NICE CG162.

What the RSST Measures

The RSST measures voluntary swallowing frequency — specifically, how many times a patient can swallow their own saliva in 30 seconds. It is a proxy measure of:

• Swallowing initiation ability — can the patient voluntarily trigger a swallow?
• Swallowing frequency and endurance — how quickly does the ability to swallow degrade with repeated effort?
• Oral preparatory capacity — can the patient generate sufficient saliva bolus to swallow repeatedly?

The RSST does not directly test swallowing safety or aspiration. It is a functional capacity measure, not a safety measure. This distinction is critical for appropriate clinical use.

Procedure

Equipment

• Stopwatch or timer (30 seconds)
• Observation of the patient’s larynx (visible through the skin of the anterior neck) or placement of a light finger contact on the larynx to detect upward movement

Positioning

Seat the patient upright if possible. Bed-bound patients can be assessed with the head of bed elevated to 30–45 degrees. Ensure the patient’s neck is accessible for palpation.

Instructions to the Patient

In English: “I’d like you to swallow as many times as you can for 30 seconds. Start when I say go, and keep going until I say stop.”

In Cantonese: 「請你盡可能多次吞嚥，由我話開始到話停止，總共30秒，準備好就開始。」

Patients with dementia may need repeated instruction and demonstration. Patients who do not understand verbal instruction cannot be validly assessed with RSST.

Counting Swallows

A swallow is counted each time the laryngeal notch (thyroid cartilage) rises and then returns to the resting position. Each complete elevation-and-return cycle = one swallow. Do not count incomplete movements or attempts that do not produce visible laryngeal elevation.

Duration

30 seconds exactly.

Scoring and Interpretation

Standard Cut-off Score

The validated cut-off for the RSST is:

• ≥3 swallows in 30 seconds = PASS (normal swallowing frequency)
• <3 swallows in 30 seconds = FAIL (reduced swallowing frequency; refer for further assessment)

Sensitivity and Specificity

Original validation by Oguchi and Saitoh (1996) against VFSS as the gold standard:

• Sensitivity for dysphagia: approximately 98%
• Specificity: approximately 66%

The high sensitivity and lower specificity makes RSST a good rule-out tool — a PASS result reasonably excludes significant swallowing dysfunction — but a FAIL does not confirm aspiration or guide management. Many patients with mild swallowing difficulty, anxiety, or dry mouth will fail without significant dysphagia.

Subsequent validation studies in hospital and residential care populations in Hong Kong and Japan have confirmed these operating characteristics with minor variation.

Modified Cut-offs for Specific Populations

Some clinical guidelines use stricter cut-offs in higher-risk populations:

• ≥4 swallows in 30 seconds as the pass criterion in some acute stroke units (where sensitivity is prioritised)
• <2 swallows as a high-risk threshold warranting immediate SLT referral (versus <3 for standard referral)

Factors Affecting RSST Performance

Xerostomia (Dry Mouth)

Patients with dry mouth (from anticholinergic medications, Sjögren’s syndrome, dehydration, radiotherapy) may produce insufficient saliva to swallow repeatedly, failing the RSST without true swallowing dysfunction. In Hong Kong care homes, anticholinergic polypharmacy is common — a positive RSST screen in these patients should be interpreted in the context of mouth dryness.

Modification: moisten the oral mucosa with a small amount of water (not enough to be swallowed as a bolus) before the test; this addresses saliva-production failure without introducing aspiration risk.

Cognitive Impairment

Patients with moderate-severe dementia may not be able to follow repeated swallow instructions. The RSST requires volitional swallowing, which is impaired in cognitively compromised patients. A failed RSST due to comprehension failure rather than physiological dysphagia should be documented as “unable to assess” rather than “failed”.

Fatigue

Patients assessed late in the day or after exertion may perform worse than at rest. Conduct RSST at a time when the patient is rested and alert.

Clinical Application in Hong Kong

The RSST is embedded in several Hong Kong institutional dysphagia screening pathways:

• Acute stroke screening (Hospital Authority): RSST as part of nurse-administered bedside dysphagia screening within 4 hours of admission for all stroke patients
• Residential care home admissions: many HKCSS-affiliated homes include RSST in admission assessment, often alongside MNA-SF and EAT-10
• Community elderly service assessments: district elderly community centres and day care settings use RSST for dysphagia surveillance in high-risk older adults

Prof. Karen Chan’s HKU Swallowing Research Lab has contributed to the adaptation and validation of RSST protocols for the Hong Kong Cantonese-speaking population, confirming that the <3 swallows/30 seconds cut-off retains its validity in Chinese older adults.

Limitations

• Does not detect silent aspiration
• Does not identify which bolus consistencies are safe or unsafe
• Cannot determine IDDSI level
• Subject to floor effects in severe dysphagia (patients scoring 0 are indistinguishable in severity)
• Not validated for patients with tracheostomy or in post-extubation settings
• Affected by xerostomia (may need modification)

RSST Within the Broader Screening Pathway

The RSST functions best as the first tier of a two-tier screening pathway:

Tier 1 — RSST: quick, no-equipment screen for all new admissions or patients with neurological risk factors. Pass → routine monitoring. Fail → tier 2.

Tier 2 — EAT-10 or GUSS: validated dysphagia screen with bolus trials and patient-reported outcomes. Fail → SLT referral.

This pathway is consistent with NICE stroke guidelines and ASHA recommendations, and has been adapted for Hong Kong hospital settings.

For referral guidance after a failed screen, see When to Refer to a Speech and Language Therapist.

References

1. American Speech-Language-Hearing Association. Adult Dysphagia Practice Portal. https://www.asha.org/practice-portal/clinical-topics/adult-dysphagia/
2. National Institute for Health and Care Excellence. Stroke Rehabilitation in Adults (CG162). https://www.nice.org.uk/guidance/cg162
3. IDDSI. The IDDSI Framework. https://www.iddsi.org/framework
4. Logemann JA, et al. (2015). Disorders of deglutition. Handbook of Clinical Neurology, 129, 465–487. PMID: 26315994