What is the best way to assess vibration?

Best Methods for Assessing Vibration Sensation

The most effective method for assessing vibration sensation is using a 128-Hz tuning fork to test large-fiber function, which should be performed along with at least one other sensory test such as 10-g monofilament testing to properly identify loss of protective sensation. 1

Proper Technique for Vibration Testing

Using a 128-Hz Tuning Fork

• Vibrate the tuning fork by striking it on your covered elbow or knee (not on hard metallic or wooden surfaces to avoid nonharmonic frequencies) 1
• Place the vibrating tuning fork on a bony prominence (typically the dorsal aspect of the distal interphalangeal joint of the great toe or other bony prominences) 1
• Ask the patient if they can feel the vibration and when the vibration stops 1, 2
• For more quantitative assessment, use the timed method where a vibrating tuning fork is placed and the time until the patient no longer feels vibration is recorded 2

Alternative Methods

• Biothesiometer testing is more accurate than tuning fork testing but less practical for bedside assessment 3
• A timed tuning fork cut-off of 4.8 seconds has been shown to be 76% sensitive and 77% specific in diagnosing mild neuropathy compared to biothesiometer readings 2
• Absent tuning fork sensation demonstrates 70% sensitivity and 90% specificity in detecting severe neuropathy 2

Comprehensive Diabetic Foot Examination Protocol

Recommended Assessment Components

• Vibration sensation using a 128-Hz tuning fork (for large-fiber function) 1
• 10-g monofilament testing (to identify feet at risk for ulceration) 1
• Temperature or pinprick sensation (for small-fiber function) 1
• Ankle reflex tests 1

When to Perform Testing

• For patients with type 1 diabetes: starting 5 years after diagnosis and at least annually thereafter 1
• For patients with type 2 diabetes: starting at diagnosis and at least annually thereafter 1
• More frequent assessments for patients with histories of ulcers, amputations, foot deformities, or peripheral arterial disease 1

Clinical Significance of Vibration Testing

• Vibration testing specifically assesses large-fiber function, which is crucial for detecting early diabetic peripheral neuropathy 1
• Loss of vibration sensation is a risk factor for diabetic foot ulceration and amputation 1
• Up to 50% of diabetic peripheral neuropathy may be asymptomatic, making objective testing essential 1

Common Pitfalls and Caveats

• The accuracy of vibration testing declines with patient age, especially in those older than 50 years 3
• Longer nerves show greater age-related decline in vibration perception 3
• Vibration testing alone is insufficient; at least two normal tests (with no abnormal test) are needed to rule out loss of protective sensation 1
• Interindividual and intraindividual variation can be high in vibration threshold measurements 4
• Vibration sense testing should be performed on bony prominences rather than soft tissue for more accurate results 1

By combining vibration testing using a 128-Hz tuning fork with other sensory tests, clinicians can effectively assess for diabetic peripheral neuropathy and identify patients at risk for foot complications, allowing for timely intervention and prevention of adverse outcomes.