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Subject of the scale: Multiple sclerosis

Expanded Disability Status Scale (EDSS)


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The EDSS is derived from the Disability Status Scale (DSS), initially described by Kurtzke in 1955 [2].

The DSS was an ordinal (non-continuous) scale consisting of 10 levels or stages of the disease, initially based on a clinical neurological examination and on the ambulatory capacity of the patient. In 1961, functional groups (similar to the functional systems (FS) used in the current version of the rating system for the EDSS) were added to the DSS. The FS scores were then used to generate scores from 0 to 4 for the DSS.

A score above 4 represented the advanced stages of the disease and depended on the patient’s ambulatory capacity (capacity to walk a short distance with or without unilateral or bilateral assistance or a wheelchair).

The DSS thus formed the base for the current EDSS which was proposed by Kurtzke in 1983 [1].
The EDSS is rated from 0 to 10 with increments of 0.5 (except between 0 and 1) while the DSS used increments of 1.

The EDSS is based on the scores of the 8 FS (pyramidal, cerebellar, brainstem, sensory, bladder and bowel, visual, cerebral and other systems, including fatigue), for scores below 4.

A score above 4 depends on the ambulatory capacity of the patient, and principally the capacity to walk a certain distance and the dependence or not on aids.

It is an ordinal (non-continuous) scale for which the quantitative distance between the scores is not well defined.

The functional systems (except the last one) represent seven parts of the central nervous system. The extent of the deficit in each is rated from normal (score of 0) to maximal (score of 5 or 6). The last functional system indicates the presence of other signs, particularly fatigue.

The EDSS is a standard clinical measure for the evaluation of neurological deficits in MS. It is used in the majority of studies which evaluate the disease progression as well as in clinical trials. It is a useful tool for the classification of patients according to the disease severity [15].

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Psychometric properties:


Psychometric properties



Face validity


Content validity


Criterion validity

Concurrent validity


Predictive validity


Construct validity

Convergent validity

[12] [14] [18]

Divergent validity


Discriminant validity
(sensitivity and distinctiveness)

[12] [14] [18]


Intra-rater reliability

[3] [8] [12]

Inter-rater reliability

[3] [4] [6] [7] [8] [12] [13] [20]



Internal consistency (alpha)

[10] [11]


[9] [11] [12] [14] [16] [17] [19] [21]

General comment on reliability:

One of the main problems of the EDSS is its lack of reliability. Most studies have found low [6], 30-50 % [4], moderate [7] or variable [14] intra and inter-rater reliability. The sensory and cerebral FS are the most variable [4].
However, for scores below 3.5, reliability is good [3, 8, 12].
Internal consistency has been found to have a bimodal distribution [10, 11].
The EDSS has a low sensitivity to change [12, 14, 16, 21] (as does the DSS [9]) (except for cerebral function [12]) and the scores tend to remain constant for a long time.
In a clinical trial, changes in scores were found to clearly reflect an improvement in the treated group and a deterioration in the placebo group [11].
In a study over a period of 2 years of patients with primary progressive MS, the sensitivity to change of the EDSS and the MSFC were found to be limited and the average change was very dependent on the initial score.
The predictive value of these two measures is not very powerful [19]. A change of at least two units of the EDSS is necessary to indicate a true clinical change [4].
The MSFC (Multiple Sclerosis Functional Composite) [16] and the MSIS (Multiple Sclerosis Impairment Scale) [17] appear to be more sensitive to change than the EDSS.
With regard to validity, the EDSS is moderately correlated with measures of disability and quality of life (particularly the SF-36, FIM and Barthel) [12].
There is a strong correlation between the PS (performance scale) and the MSFC and EDSS. The EDSS has been found to have convergent and discriminant validity but its degree of precision (specificity) is limited compared with the FIM [14].
According to several authors [5], the EDSS has some serious failures which significantly limit its usefulness, particularly a lack of precision regarding the definition of the degree of the deficit in some functional categories of the scale, as well as the use of a variety of neurological signs taken from the clinical assessment and the subjective examination in the overall definition of the scale.
A computerised assessment (MS-CANE) significantly improves the reliability of the EDSS. Moreover, strong correlations have been found between the MS-CANE and the traditional evaluation by the EDSS [13].
Equally, the AEDSS (Automatic EDSS) reduces inter rater variability and in some cases evaluation errors can also be corrected [20]. The level of evidence is higher than the standard EDSS. The AEDSS has been validated for clinical practice.
A standardised protocol, NEUROSTATUS, has been developed to reduce potential inter-rater variability for the administration and rating of the EDSS: Kappos L, Lechner-Scott J, Lienert C. Neurostatus: Standardized Neurological Examination and Assessment of Kurtzke's Functional Systems and Expanded Disability Status Scale (training CDROM for a standardized neurologic examination and assessment of Kurtzke's functional systems and expanded disability status scale for MS patients). Basel: Point de Vue Audio-Visual Productions, 1999.

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Inaugural references:

[1] Kurtzke JF. Rating neurologic impairment in multiple sclerosis: an expanded disability status scale (EDSS). Neurology. 1983 Nov;33(11):1444-52.

Psychometric references:

[2] Kurtzke JF. A new scale for evaluating disability in multiple sclerosisNeurology. 1955 Aug;5(8):580-3.

[3] Amato MP, Groppi C, Siracusa GF, Fratiglioni L. Interrater and intra-observer reliability in Kurtzke scoring systems in multiple sclerosis. Ital J Neurol Sci. 1987 Jun;Suppl 6:129-31.

[4] Amato MP, Fratiglioni L, Groppi C, Siracusa G, Amaducci L. Interrater reliability in assessing functional systems and disability on the Kurtzke scale in multiple sclerosis. Arch Neurol. 1988 Jul;45(7):746-8.

[5] Willoughby EW, Paty DW. Scales for rating impairment in multiple sclerosis: a critique. Neurology. 1988 Nov;38(11):1793-8.

[6] Noseworthy JH, Vandervoort MK, Wong CJ, Ebers GC. Interrater variability with the Expanded Disability Status Scale (EDSS) and Functional Systems (FS) in a multiple sclerosis clinical trial. The Canadian Cooperation MS Study Group. Neurology. 1990 Jun;40(6):971-5.

[7] Francis DA, Bain P, Swan AV, Hughes RA. An assessment of disability rating scales used in multiple sclerosis. Arch Neurol. 1991 Mar;48(3):299-301.

[8] Goodkin E. "EDSS reliability. Neurology." 1991 Feb;41(2 ( Pt 1)):332.

[9] Ellison GW, Myers LW, Leake BD. Responsiveness of the Disability Status Scale (DSS) [abstract]. Neurology 1993; 43 (2 Suppl 1): A204.

[10] Rodriguez M, Siva A, Ward J, Stolp-Smith K, O'Brien P, Kurland L. Impairment, disability, and handicap in multiple sclerosis: a population-based study in Olmsted County, Minnesota. Neurology. 1994 Jan;44(1):28-33.

[11] Koziol JA, Frutos A, Sipe JC, Romine JS, Beutler E. A comparison of two neurologic scoring instruments for multiple sclerosis. J Neurol. 1996 Mar;243(3):209-13.

[12] Sharrack B, Hughes RA, Soudain S, Dunn G. "The psychometric properties of clinical rating scales used in multiple sclerosis." Brain. 1999 Jan;122 ( Pt 1):141-59.

[13] Cohen YC, Hassin-Baer S, Olmer L, Barishev R, Goldhammer Y, Freedman L, Mozes B. MS-CANE: a computer-aided instrument for neurological evaluation of patients with multiple sclerosis: enhanced reliability of expanded disability status scale (EDSS) assessment. Mult Scler. 2000 Oct;6(5):355-61.

[14] Hobart J, Freeman J, Thompson A. Kurtzke scales revisited: the application of psychometric methods to clinical intuition. Brain. 2000 May;123 ( Pt 5):1027-40.

[15] Balcer LJ. Clinical outcome measures for research in multiple sclerosis. J Neuroophthalmol. 2001 Dec;21(4):296-301.

[16] Patzold T, Schwengelbeck M, Ossege LM, Malin JP, Sindern E. Changes of the MS functional composite and EDSS during and after treatment of relapses with methylprednisolone in patients with multiple sclerosis. Acta Neurol Scand. 2002 Mar;105(3):164-8.

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