The DS is an ordinal clinical rating scale developed by Hohol et al (1995) to provide a straightforward assessment of functional disability in MS primarily based on ambulation. It was designed to aid in determining when to implement therapy and as a way to monitor treatment response. Scores range from 0 (normal) to 6 (essentially confined to wheelchair). There is a separate category for patients who are not classifiable. The rating itself is simple and brief. However, the information needed to arrive at a rating generally requires a medical history and both general physical and neurological examinations, including having the patient walk 25 feet.
Administration time will vary depending upon the ability of the patient. Total administration time should be approximately 1-5 minutes. Although the DS itself can be rated in a few minutes, the medical history and neurological examination that may be needed to make the ratings can take anywhere from 15 minutes to a half-hour.
The DS is administered in person by a trained examiner, most often a neurologist. However, nurse practitioners with the proper training can also complete the neurological examination and rate the DS.
Based on information gleaned from a patient's history and neurological examination, the patient is rated on an ordinal scale ranging from 0 (normal) to 6 (essentially confined to a wheelchair). There is an additional category, "U" for patients who cannot be classified into one of the 0-6 ranks. Download the Disease Steps Form (PDF)
The DS is also available in the original journal article where it was first published, Hohol, et al (1995).
The DS is similar to the EDSS but with more consistent intervals represented by the different grades, better sensitivity, and better inter-rater reliability. One of the strengths of the DS appears to be its simplicity and since its publication, a number of modified versions have been used that allow patients to rate themselves.
Inter-rater reliability is good with weighted Kappa of .80. Concurrent validity was good in the original study with a Spearman Rank Order Correlation of .96 between the DS and the EDSS. When the DS and EDSS were compared in the same patients, the DS showed a reasonably smooth distribution whereas the EDSS showed a characteristic bimodal distribution with peaks in the low and high end of the scale and a trough in the middle.