Validity and reliability of the Katz-15 scale to measure unfavorable health outcomes in community-dwelling older people.
OBJECTIVE
To predict the risk of future unfavourable health outcomes in older people it is common to assess the level of both basic and instrumental activities of daily living. To accomplish this, the commonly used Katz-6 and the Lawton IADL questionnaires can be combined to form the 'Modified Katz ADL' scale, also known as the Katz-15 scale. So far, the validity and reliability of the Katz-15 scale is unknown. The objective of the current study is to investigate how well the Katz-15 is able to predict future unfavorable health outcomes and how this is related to the existing Katz-6 scale.


METHODS
We performed a follow-up study using data from a group of 60 year and older participants from a large Dutch clinical trial.


METHODS
We included 2321 participants in the analysis. The average age of the study population was 74 years and 44% was male.


METHODS
We studied the relation between the Katz-15 scale and a number of unfavourable health outcomes, such as hospitalization, admission to a nursing home, admission to a home for the aged and death within one year of follow-up.


RESULTS
We found the Katz-15 to be both internally consistent and strongly associated with quality of life measures. We observed moderate to strong associations between the Katz-15 and the unfavourable health outcomes All associations studied were stronger for the Katz-15 scale as compared to the Katz-6 scale.


CONCLUSIONS
The results of our study indicate that the Katz-15 scale is able to reliably and validly predict future unfavorable health outcomes. This makes the scale a valuable measure in determining both basic and instrumental activities of daily living.
Wijnand Laan, Assistant Professor, Julius Center for Health Sciences and Primary Care, University Medical Center Utrecht, Str. 6.131, P.O. Box 85500, 3508 GA Utrecht, The Netherlands.
W
W
Laan
N P A
NP
Zuithoff
I
I
Drubbel
N
N
Bleijenberg
M E
ME
Numans
N J
NJ
de Wit
M J
MJ
Schuurmans
D000203:Activities of Daily Living; D000368:Aged; D002986:Clinical Trials as Topic; D005260:Female; D005500:Follow-Up Studies; D015577:Geriatric Assessment / Q000379:methods*; D006707:Homes for the Aged / Q000706:statistics & numerical data; D006760:Hospitalization / Q000706:statistics & numerical data; D006801:Humans; D008297:Male; D009026:Mortality; D009426:Netherlands; D009735:Nursing Homes / Q000706:statistics & numerical data; D011788:Quality of Life; D015203:Reproducibility of Results; D012111:Residence Characteristics; D018570:Risk Assessment / Q000379:methods; D011795:Surveys and Questionnaires