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Formal measurements of physical impairments and disability include diagnostic tests and standardized medical summaries of a patient's condition; they are typically used with elderly or chronically ill patients. These are mostly ratings applied by a clinician and can include range of motion, grip strength and gait. These are often used in assessing fitness for work or in reviewing claims for accident and injury compensation; the emphasis is on standardized ratings that can withstand legal examination.
Physical impairments can be accurately assessed, but they are not the only factor that predicts a patient's need for care: environmental factors, the availability of social support and the patient's determination all affect how far an impairment will be translated into disability or handicap. Hence, for evaluating patient rehabilitation, we need measures of disability and handicap as well.
Starting in the 1950s and 1960s, routine clinical assessments were broadened to consider the activities a patient could or did perform at his level of physical capacity. These assessments are generally termed "functional capacity" or "functional disability" indicators. An early example was Sidney Katz's 1957 Index of Independence in Activities of Daily Living. Mostly used for elderly patients in a rehabilitation setting, this summarizes their degree of independence in bathing, dressing, using the toilet, eating and moving around the ward – topics that Katz chose to represent "primary biological functions." The results can be presented as a single score, or as a profile of the level of function in each area covered. There are now many such measures, each giving the clinician (or researcher) guidelines on completing the assessment; many can be completed by the patient themselves via a questionnaire.
In 1969, Lawton and Brody extended the ADL concept to consider problems more typically experienced by those living in the community: mobility, difficulty in shopping, cooking, or managing money, a field that came to be termed "Instrumental Activities of Daily Living" (IADL) or "Performance Activities of Daily Living" (PADL). Instrumental activities are more complex and demanding than basic ADLs; they offer indicators of applied problems that include elements of the handicap concept. They are relevant in assessing a patient's ability to live independently in the community.
Frailty. Most recently, the concept has been further broadened to include the notion of "frailty". This is defined in differing ways, but refers the overall effect of aging, disease, and factors such as nutritional status and functional ability that make some persons vulnerable to adverse health outcomes. It is a prognostic concept, referring to people at risk of decline in health; it is the opposite of successful aging.
Mnemonics can help you recall the topics typically covered in ADL scales. A somewhat unfortunate one is DEATH, for dressing, eating, ambulating, toileting, and hygiene. For instrumental ADL tasks, SHAFT = shopping, housekeeping, accounting, food-preparation, transportation.
More detail: You may wish to distinguish between a person's physical capacity and his actual performance in managing his life in the face of physical limitations. There are two ways of phrasing questions on functional disability: you can ask what the patient can do (the "capacity" wording) or what she does do ("performance" wording). Both hold advantages and disadvantages. Asking what a patient can do may provide a hypothetical answer - what he thinks he can do even though he does not normally attempt it. This phrasing can exaggerate the healthiness of the respondent, perhaps by as much as 20%. The performance wording may run the opposite risk. Performance may be restricted by factors other than health, so performance questions may under-estimate potential. An intermediate phrasing can be used, such as "Do you have difficulty with . . .?
Updated August 26, 2011