Physical Function and ADL Assessment Instruments

Physical function instruments describe what a person can do rather than what is wrong with them, and they are organised by how demanding the activity is. Basic activities of daily living scales such as the Barthel Index and the Katz ADL Index cover self-care: eating, washing, dressing, transferring, continence. Instrumental scales such as the Lawton IADL Scale, the Frenchay Activities Index and the Nottingham Extended ADL Index cover the harder tasks that keep someone living independently, including shopping, cooking, managing money and using transport. Global disability measures such as the Modified Rankin Scale and the WHO Disability Assessment Schedule summarise the whole picture in one grade.

Capacity measures such as the Duke Activity Status Index and the 6-Minute Walk Test sit slightly apart. They estimate what someone is physically able to sustain rather than what they routinely do, and the two often diverge.

The choice between basic and instrumental scales is usually settled by the population. Basic ADL scales have strong ceiling effects in community-dwelling people, most of whom score at or near the maximum, so they cannot detect the changes that matter to someone living at home. Instrumental scales have the opposite problem in inpatient rehabilitation, where many of the activities are simply not attempted.

There is also a persistent distinction between capacity and performance that these instruments handle differently. Some ask what the person can do, some ask what they actually did in a defined period, and some leave it ambiguous. The distinction matters because interventions frequently change capacity without changing performance, and a study that measures one while expecting the other will report a null result for the wrong reason.

Check who reports. Several of these instruments can be completed by the patient, by a carer or by a clinician, and the three do not agree. Carers tend to rate independence lower than patients do. Whichever source is used, it must be the same source at every timepoint, and the source should be recorded with the score.

Check the ceiling against the population before committing. This is the most common avoidable failure in this group, and it is visible at baseline if anyone looks.

Check the scoring convention. Some instruments in this family have several published scoring variants with different ranges, and the Barthel Index in particular circulates in more than one form. Scores from different variants are not comparable, so record which version was used rather than only the total.

What is the difference between basic and instrumental activities of daily living?

Basic activities are self-care tasks such as eating, washing, dressing and transferring. Instrumental activities are the more complex tasks needed to live independently, such as shopping, cooking, managing medication and handling money. Instrumental ability is usually lost first, which is why instrumental scales detect early decline that basic scales miss.

Why do my ADL scores show no improvement?

Check the baseline distribution first. If most participants started at or near the maximum score, the instrument had no room to record improvement. In community populations a basic ADL scale will often behave this way, and an instrumental or extended scale is the better choice.

Can a family member complete these questionnaires?

Yes for many of them, but proxy and self-report are not interchangeable. Proxies tend to report more dependence than the person does. Fix the reporting source at the start of the study, keep it constant, and record it alongside every score.

Which instrument should I use to measure disability after stroke?

It depends on the granularity needed. The Modified Rankin Scale gives a single global grade and is widely used as a trial endpoint. The Barthel Index gives more detail on self-care. Extended and instrumental scales capture the community-level recovery that the other two miss.