A validation study of the daily activities questionnaire: an activities of daily living assessment for people with Alzheimer's disease. (Oakley F, 1999)

Oakley F, L. J., Sunderland T. (1999). A validation study of the daily activities questionnaire: an activities of daily living assessment for people with Alzheimer's disease. Journal of outcome measurement, 3(4), 297-307.

National Institutes of Health, Warren G. Magnuson Clinical Center, Bethesda, MD 20892-1604, USA. Fran_Oakley@nih.gov

Abstract: The Daily Activities Questionnaire (DAQ) was developed to assess activities of daily living (ADL) independence in people with Alzheimer's disease. After administering it to 276 people diagnosed with Alzheimer's disease, we examined the quality of the rating scale and its structure using a Rasch measurement approach. Results indicated that the original 10-point rating scale should be restructured to a 5-point rating scale to improve the quality of the instrument. In addition, we found that all but two ADL items defined the same construct and could be combined into a single summary measure of ADL independence. The remaining items were positioned along a hierarchical continuum, with IADL tasks more difficult than PADL tasks. Furthermore, the tasks were logically ordered by difficulty. We therefore report that the DAQ is a valid scale and conclude that it is a viable measure of ADL independence for studies of Alzheimer's disease.

http://www.ncbi.nlm.nih.gov/pubmed/10572383

My Note:

Daily activities questionnaire (Oakley, et al., 1991)

• PADL assess independence in individual: bathing, dressing, toileting, walking, eating and grooming
• IADL: Home care, cooking, shopping, finances, and phone use.

Some interesting rule of thumbs for Rasch analysis:

"Rasch analysis determines the unidimensionality of the instrument by examining response patterns of the items in the instrument, which are demonstrated by infit Mean Square (MnSq) statistics. The MnSq is the ratio between observed and expected variance (Wright and Masters, 1982).

An acceptable range for an infit MnSq value for a rating scale is between .6 and 1.4 (Wright and Masters, 1994). An item with a MnSq value smaller than 0.6 indicates that the item does not provide additional information beyond the rest of items on the scale. If the MnSq value for an item is greater than 1.4, either the item does not define the same construct as the rest of the items in the instrument or it is ambiguously defined.

Rasch analysis also provides a significance test for the MnSq value. A Zstd value greater than 2.0 indicates that the corresponding MnSq value is significant at the .05 level."

Due to the disordered steps in the 10 category scenario, the authors converted the original 10-point rating scale to a 5-point rating scale.

One final word for this study…. The authors consider the combined scale of ADL/IADL as unidimensional….

http://www.rasch.org/rmt/rmt82a.htm

Oakley and his associated conducted a study to assess the Validity of the Daily Activities Questionnaire (DAQ) (Oakley et al 1991). The DAQ is an 14-item instrument which was designed to assess independence in PADL (ADL) and IADL. The participants of the study were individuals diagnosed with Alzheimer's disease and who were institutionalized. The authors used the FACETS software to assess the fit of Rasch Model for the data. After the initial analyses, the authors the 10-point scale into a 5-point scale because they found the original 10-point rating scale to have limited ability in discriminating among patients' ability; they also dropped walking as an unfit item from the final analyses. Results of the Rasch analysis supports the notion of unidimensionality or an underlying ADL construct; in addition, based on results about the level of endorsability of the items, it is found that the DAQ items are spread across a hierarchical linear continuum where IADL items were found to be more difficult than PADL (ADL) items at least for patients with Alzheimer disease..