Dysphagia Knowledge Hub — 吞嚥困難知識庫

Water Swallow Test (WST)

Overview

The Water Swallow Test (WST) is one of the oldest and most widely used bedside dysphagia screening tools. It involves administering standardised volumes of water and observing for signs of aspiration or swallowing difficulty. Despite its simplicity, it has demonstrated reasonable sensitivity for aspiration risk and is recommended in multiple stroke and dysphagia clinical guidelines.

Two primary variants are in common clinical use:

Kubota 50 mL WST: The patient swallows 50 mL of water as continuously as possible, scored on number of swallows, time taken, coughing, and choking.
Daniels 3-oz Water Swallow Test (3-oz WST): The patient drinks 90 mL (3 fluid ounces) of water continuously; coughing or a wet/gurgly voice quality within 1 minute of completion constitutes a positive screen.

Kubota 50 mL WST Protocol

Indication: Acute stroke, post-extubation, other acute neurological conditions.

Contraindications: Drowsy or uncooperative patient; frank drooling or inability to close lips; known severe aspiration; tracheostomy.

Method:

Seat patient upright (≥90°) or head of bed ≥60°.
Provide 50 mL of room-temperature water in a cup.
Instruct patient: “Drink this water in one continuous attempt if possible.”
Observe and record:
- Time to complete (seconds)
- Number of swallows required
- Presence of cough during or within 1 minute after
- Wet/gurgly voice quality — ask patient to say “ah” immediately after

Kubota Grading:

Grade 1: Drank 50 mL in single swallow, no cough, <5 seconds — Normal
Grade 2: Drank in 2+ swallows or >5 seconds, no cough — Mild
Grade 3: Drank in single swallow with cough — Moderate
Grade 4: Drank in 2+ swallows with cough — Severe
Grade 5: Unable to drink entire 50 mL, frequent choking — Very severe

Grades 3–5 = abnormal screen; refer to SLT.

Daniels 3-oz Water Swallow Test

Indication: Preferred for community and outpatient settings; widely used in US stroke rehabilitation.

Method:

Patient seated upright.
Provide 90 mL (3 oz) of water in a cup with no straw.
Instruct: “Drink all of this water without stopping if you can.”
Observe during drinking and for 1 minute after.

Positive screen (refer to SLT): Any cough during or within 1 minute of drinking, OR wet/gurgly voice quality within 1 minute.

Sensitivity: ~70–80% for aspiration on VFSS (Suiter & Leder, 2008; DOI: 10.1007/s00455-007-9127-y) Specificity: ~59–70%

Sensitivity and Specificity Summary

Variant	Sensitivity (aspiration)	Specificity	Notes
Kubota 50 mL	~65–75%	~65–75%	Widely used in Asia
Daniels 3-oz	~70–80%	~59–70%	Strong negative predictive value
Combined with EAT-10	Higher specificity	—	Reduces false positives

The 3-oz test in particular has a high negative predictive value (~90%) — a patient who passes without coughing or wet voice has a low probability of aspiration on VFSS, supporting safe oral intake initiation without instrumental assessment in many cases.

Silent Aspiration Limitation

The WST’s primary limitation is its inability to detect silent aspiration — aspiration without cough or voice change. Studies using VFSS show that 40–50% of patients who aspirate on VFSS do not cough during the WST (Leder & Suiter, 2010; DOI: 10.1007/s00455-010-9284-1).

This means a negative WST does not rule out aspiration, particularly in:

Patients with reduced laryngeal sensation (post-stroke, post-radiotherapy)
Patients with impaired cough reflex (Parkinson’s, advanced dementia)
Elderly patients generally

In these populations, a negative WST should be supplemented by the full GUSS protocol or instrumental assessment.

Clinical Recommendations

Use WST as a first-line screen in acute stroke (within 4 hours of admission, before oral intake).
Combine WST with EAT-10 to improve specificity.
A positive WST → refer to SLT for clinical swallowing examination (CSE) before initiating oral diet.
A negative WST in high-risk populations (Parkinson’s, advanced dementia) → still proceed to CSE due to silent aspiration risk.
Document all findings including patient position, water temperature, and volume consumed.

References

Suiter DM, Leder SB (2008). Clinical utility of the 3-ounce water swallow test. Dysphagia, 23(3):244–50. DOI: 10.1007/s00455-007-9127-y
Leder SB, Suiter DM (2010). An epidemiologic study on aging and dysphagia in the acute care hospitalized population: a replication and continuation study. Dysphagia, 25(2):182–6. DOI: 10.1007/s00455-009-9234-4
DePippo KL, et al. (1992). Dysphagia therapy following stroke: a controlled trial. Neurology, 44(9):1655–60. PMID: 7936295
Bours GJ, et al. (2009). Bedside screening tests vs. videofluoroscopy or fibreoptic endoscopic evaluation of swallowing to detect dysphagia in patients with neurological disorders. J Adv Nurs, 65(3):477–93. DOI: 10.1111/j.1365-2648.2008.04915.x