The AMC Linear Disability Score project in a population requiring residential care: psychometric properties.
BACKGROUND
Currently there is a lot of interest in the flexible framework offered by item banks for measuring patient relevant outcomes, including functional status. However, there are few item banks, which have been developed to quantify functional status, as expressed by the ability to perform activities of daily life.


METHODS
This paper examines the psychometric properties of the AMC Linear Disability Score (ALDS) project item bank using an item response theory model and full information factor analysis. Data were collected from 555 respondents on a total of 160 items.


RESULTS
Following the analysis, 79 items remained in the item bank. The remaining 81 items were excluded because of: difficulties in presentation (1 item); low levels of variation in response pattern (28 items); significant differences in measurement characteristics for males and females or for respondents under or over 85 years old (26 items); or lack of model fit to the data at item level (26 items).


CONCLUSIONS
It is conceivable that the item bank will have different measurement characteristics for other patient or demographic populations. However, these results indicate that the ALDS item bank has sound psychometric properties for respondents in residential care settings and could form a stable base for measuring functional status in a range of situations, including the implementation of computerised adaptive testing of functional status.
Holman
Rebecca
R
Department of Clinical Epidemiology and Biostatistics, Academic Medical Center, Amsterdam, The Netherlands. r.holman@amc.uva.nl
Lindeboom
Robert
R
Vermeulen
Marinus
M
de Haan
Rob J
RJ
D000203:Activities of Daily Living / Q000145:classification*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003625:Data Collection / Q000379:methods; D004185:Disability Evaluation; D005260:Female; D006305:Health Status Indicators; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D010865:Pilot Projects; D011336:Probability; D011594:Psychometrics / Q000295:instrumentation*; D012112:Residential Facilities / Q000706:statistics & numerical data*; D012720:Severity of Illness Index; D011795:Surveys and Questionnaires / Q000592:standards