Ambulation Index (AI)
The AI is a rating scale developed by Hauser et al (1983) to assess mobility by evaluating the time and degree of assistance required to walk 25 feet. Scores range from 0 (asymptomatic and fully active) to 10 (bedridden). The patient is asked to walk a marked 25-foot course as quickly and safely as possible. The examiner records the time and type of assistance (e.g., cane, walker, crutches) needed.
Administration time will vary depending upon the ability of the patient. Total administration time should be approximately 1-5 minutes.
The AI is administered in person by a trained examiner. The examiner need not be a physician or nurse.
Although the patient's walking is timed, the time is not used directly but is utilized in conjunction with other factors to rate the patient on an ordinal scale with 11 gradations.
The AI is also available in the original journal article where it was first published, Hauser et al (1983).
Gait speed in general has been demonstrated to be a useful and reliable functional measure of walking ability. The AI is similar to and has been largely replaced by the Timed 25-Foot Walk (T25-FW). While the AI uses an ordinal clinical rating of a performance category, the T25-FW measures the actual time needed to complete the task. When administering the AI, patients are allowed to use assistive devices (canes, crutches, walkers). In addition the rating scale has categories for patients who are unable to walk at all.
The AI has demonstrated good test-retest and inter-rater reliability as well as good convergent validity. However, because of its more desirable psychometric properties, the 25-Foot Timed Walk has largely replaced the AI in clinical studies.