What are the Visual Analog Scale (VAS) and Neck Disability Index (NDI) in the context of assessing neck pain?

Visual Analog Scale (VAS) and Neck Disability Index (NDI)

Visual Analog Scale (VAS)

The VAS is a standardized pain intensity measurement tool consisting of a 100-mm horizontal line where patients mark their current pain level, with 0 representing no pain and 100 representing worst imaginable pain. 1

Key Characteristics of VAS:

• Most frequently used standardized scale for assessing pain intensity in cancer pain management and chronic pain conditions 1
• Provides a continuous measurement allowing detection of small changes in pain intensity 1
• Demonstrates high responsiveness to treatment effects, with a weighted mean difference of 12 mm on the 100-mm scale considered clinically significant (p < 0.001) 1
• Used alongside other pain scales including the Verbal Rating Scale (VRS) and Numerical Rating Scale (NRS) for comprehensive pain assessment 1

Clinical Application:

• Regular self-reporting using VAS is the first step toward effective and individualized pain treatment 1
• Particularly useful in research settings to assess outcome variables across diverse patient populations 1
• Concurrent validity established through strong correlations with disability measures (r = 0.508-0.620, p < 0.0001) 2

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Neck Disability Index (NDI)

The NDI is a 10-item self-administered questionnaire specifically designed to measure disability and functional limitations caused by neck pain, with scores ranging from 0 (no disability) to 50 (complete disability). 1

Psychometric Properties:

• Demonstrates excellent test-retest reliability with intraclass correlation coefficients ranging from 0.68 to 0.93 1, 3
• High internal consistency with Cronbach's alpha values of 0.83-0.92 3, 4, 5
• Strong construct validity demonstrated through correlations with SF-36 domains (r = -0.34 to -0.74, all p < 0.001) 4, 5
• Item-total correlations range from 0.40 to 0.73, indicating robust internal structure 4, 5

Clinical Utility:

• Validated for use in patients with cervical radiculopathy, neck pain, and cervical spine disorders 1
• Minimal detectable change is 10.2 points, indicating the threshold for clinically meaningful improvement 1
• Successfully translated into 22 languages with maintained psychometric properties 6
• Endorsed by multiple clinical guidelines as the most widely used and strongly validated instrument for neck pain disability assessment 6

Assessment Domains:

The NDI evaluates 10 specific functional areas affected by neck pain 3, 6:

• Pain intensity
• Personal care activities
• Lifting
• Reading
• Headaches
• Concentration
• Work
• Driving
• Sleeping
• Recreation

Limitations to Consider:

• The NDI shows inferior responsiveness compared to the Patient-Specific Functional Scale (PSFS) in detecting change over time (minimal detectable change 10.2 vs 2.1) 1
• Failed to demonstrate construct validity in one study when comparing stable versus improved patients based on global rating of change 1
• Floor and ceiling effects may occur in specific items, though overall scale performance remains robust 5

Clinical Decision Points:

• Use NDI at baseline and follow-up to quantify disability levels in patients with neck pain 1
• Combine with VAS for comprehensive assessment of both pain intensity and functional impact 4, 5, 2
• A change of ≥10 points on the NDI represents clinically meaningful improvement requiring treatment modification 1
• Scores correlate strongly with SF-36 physical function domains, validating its use as a disease-specific outcome measure 4, 5