Psychometrics

Original research by Lawton and Brody (1969) found that the measure was highly reproducible with test-retest reliability coefficients of 0.96 (n = 97) and 0.93 (n = 168), respectively. Work of two independent raters included in the original study also found inter-rater agreement to be good at 0.85 between total scores. The IADL scale was found to correlate well with several outcome measures such as the Physical Self-Maintenance Scale at 0.61, Mental Status Questionnaire at 0.48, Behavior and Adjustment Rating Scales at 0.44, and the Physical Classification at 0.40 (Lawton & Brody, 1969). Burton et al. (2009) found that the correlation between the self- and informant-based versions of the scale was 0.69. Between age and education for the self-report it was 0.24 and –0.10 and for the informant-report it was 0.22 and –0.10. The IADL scale also showed a significant negative correlation with the Scales of Independent Behavior-Revised; and since each test is both a self- and informant-based measure, concurrent validity was compared between each separately. For the self-report it was –0.58 and for the informant versions it was –0.69. A study of falls by Chu, Chiu, and Chi (2006) found that when comparing the IADL Scale with the Barthel Index, Tinetti Balance Scale and gait speed, after gait speed the IADL Scale was able to predict the occurrence of falls among community dwelling residents over 65 years old. A study by Cromwell, Eagar, and Poulos (2003) found that three IADL items (telephone use, self-medication, and handling finances) were statistically associated with cognitive impairment. A similar study found four IADL items were associated with cognitive impairment regardless of age, sex, or education: telephone use, use of transportation, self-medication, and handling finances (Barberger-Gateau et al., 1992). A study by McGrory, Shenkin, Austin, and Starr (2014) found shopping and food preparation to be the most difficult items and considered to be lost first in the disablement process while telephone use was the least difficult, suggesting that a person reporting challenges with telephone use is unlikely to be able to perform any other task on the scale. Conversely, if a person reports no problems with shopping or food preparation they will likely have no limitations with other tasks.

Advantages

Disadvantages

Developed in 1969, the Lawton IADL Scale has remained relatively unchanged and because of the simple scoring system (0 or 1 with a high score of 8) some researchers have noted a lack of sensitivity to detect small changes in functional status. Others have noted that although statistical differences fall within acceptable limits, gender bias may exist for items relating to food preparation, laundry, and housekeeping.

Administration

The Lawton IADL Scale is a questionnaire that is completed by proxy, as a self-report, or through interview where the subject is asked to consider items relative to his or her ability to engage in activities considered important for independence. Several researchers have suggested and tested different scoring models to improve the sensitivity of the measure and its ability to document change beyond the original dichotomous scale of (0 = less able, 1 = more able) to include a 3-point scale (1 = unable, 2 = needs assistance, 3 = independent) as well as a 4-point scale. A study examining all 3 scoring systems found reliability estimates to be high respectively for each scoring system at r = 0.80, 0.88, and 0.87, suggesting near equal validity when using the original or more complex scoring systems (Graf, 2008).

Permissions

The assessment is located in the public domain and is free to use in clinical practice. It can also be found in its entirety in several publications as well as online. Permission to use in research and/or publication can be obtained by contacting the publishers of the original work or the Copyright Clearance Center at the information following. Further information can be found in the following journal article:

Lawton, M. P., & Brody, E. M. (1969). Assessment of older people: Self-maintaining and instrumental activities of daily living. The Gerontologist, 9, 179-186.

Summary

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