Kurtzke Expanded Disability Status Scale

The 10-point Kurtzke Expanded Disability Status Scale (EDSS) is the most widely accepted clinical disability scale. ^[1]

The EDSS is considered the standard for monitoring patients with multiple sclerosis (MS), including those in MS clinical research, although MS is difficult to assess because of the differences in signs and symptoms. ^{[2, 3, 4, 5]}

The EDSS assigns a severity score to the patient's clinical status that ranges from 0-10 in increments of 0.5. The scores from grades 0-4 are determined using functional systems (FS) scales that evaluate dysfunction in the following 8 neurologic systems:

• Pyramidal

• Cerebellar

• Brainstem

• Sensory

• Bladder and bowel

• Vision

• Cerebral

• Other

EDSS grades are as follows:

• 0 - Normal neurologic examination (all grade 0 in FS, cerebral grade 1 acceptable)

• 1.0 - No disability, minimal signs in 1 FS (ie, grade 1 excluding cerebral grade 1)

• 1.5 - No disability, minimal signs in more than 1 FS (more than 1 grade 1 excluding cerebral grade 1)

• 2.0 - Minimal disability in 1 FS (1 FS grade 2, others 0 or 1)

• 2.5 - Minimal disability in 2 FS (2 FS grade 2, others 0 or 1)

• 3.0 - Moderate disability in 1 FS (1 FS grade 3, others 0 or 1) or mild disability in 3 or 4 FS (3/4 FS grade 2, others 0 or 1) though fully ambulatory

• 3.5 - Fully ambulatory but with moderate disability in 1 FS (1 grade 3) and 1 or 2 FS grade 2, or 2 FS grade 3, or 5 FS grade 2 (others 0 or 1)

• 4.0 - Fully ambulatory without aid; self-sufficient; up and about some 12 hours a day despite relatively severe disability, consisting of 1 FS grade 4 (others 0 or 1) or combinations of lesser grades exceeding limits of previous steps; able to walk approximately 500 m without aid or resting

• 4.5 - Fully ambulatory without aid; up and about much of the day; able to work a full day; may otherwise have some limitation of full activity or require minimal assistance; characterized by relatively severe disability, usually consisting of 1 FS grade 4 (others 0 or 1) or combinations of lesser grades exceeding limits of previous steps; able to walk approximately 300 m without aid or rest

• 5.0 - Ambulatory without aid or rest for approximately 200 m; disability severe enough to impair full daily activities (eg, to work full day without special provisions; usual FS equivalents are 1 grade 5 alone, others 0 or 1; or combinations of lesser grades usually exceeding specifications for step 4.0)

• 5.5 - Ambulatory without aid or rest for approximately 100 m; disability severe enough to preclude full daily activities (usual FS equivalents are 1 grade 5 alone; others 0 or 1; or combinations of lesser grades usually exceeding those for step 4.0)

• 6.0 - Intermittent or unilateral constant assistance (cane, crutch, or brace) required to walk approximately 100 m with or without resting (usual FS equivalents are combinations with more than 2 FS grade 3+)

• 6.5 - Constant bilateral assistance (canes, crutches, or braces) required to walk approximately 20 m without resting (usual FS equivalents are combinations with more than 2 FS grade 3+)

• 7.0 - Unable to walk beyond approximately 5 m even with aid; essentially restricted to wheelchair; wheels self in standard wheelchair and transfers alone; up and about approximately 12 hr/day (usual FS equivalents are combinations with more than 1 FS grade 4+; very rarely, pyramidal grade 5 alone)

• 7.5 - Unable to take more than a few steps; restricted to wheelchair; may need aid in transfer; wheels self but cannot carry on in standard wheelchair a full day; may require motorized wheelchair (usual FS equivalents are combinations with more than 1 FS grade 4+)

• 8.0 - Essentially restricted to bed or chair or perambulated in wheelchair but may be out of bed itself much of the day, retains many self-care functions; generally has effective use of arms (usual FS equivalents are combinations, generally grade 4+ in several systems)

• 8.5 - Essentially restricted to bed much of the day; has some effective use of arms; retains some self-care functions (usual FS equivalents are combinations, generally 4+ in several systems)

• 9.0 - Helpless bedridden patient; can communicate and eat (usual FS equivalents are combinations, mostly grade 4+)

• 9.5 - Totally helpless bedridden patient; unable to communicate effectively or eat/swallow (usual FS equivalents are combinations, almost all grade 4+)

• 10.0 - Death due to MS

Advantages of the EDSS are that it is widely used clinically, is easy to administer, and requires no special equipment. Its limitations are as follows:

• It is heavily dependent on mobility

• It is somewhat subjective in certain areas (eg, bowel and bladder function and cerebral function)

• It is insensitive to small changes

• It does not present an accurate picture of the patient's cognitive abilities and functional abilities in performing activities of daily living (ADLs)

• It is nonlinear in terms of the time spent at various ranges of the scale

Several supplemental evaluations have been proposed to ameliorate the limitations of the scale, including the following:

• Implementation of the Brief International Cognitive Assessment for MS (BICAMS) scale to reduce the subjectivity of the cognitive portion, especially in patients with an EDSS score of 4.0 or more. ^[6]
• The combined use of the Timed 25-Foot Walk (T25FW), 9-Hole Peg Test (9HPT), Low Contrast Letter Acuity (LCLA), and Symbol Digit Modalities Test (SDMT), along with EDSS to increase the sensitivity to detect disease progression. ^[7]

Despite its limitations, the EDSS often is used as a standardization measure for clinical trials.