The Academic Medical Center Linear Disability Score (ALDS) item bank: item response theory analysis in a mixed patient population.
BACKGROUND
Currently, there is a lot of interest in the flexible framework offered by item banks for measuring patient relevant outcomes. 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. This paper examines the measurement properties of the Academic Medical Center linear disability score item bank in a mixed population.


METHODS
This paper uses item response theory to analyse data on 115 of 170 items from a total of 1002 respondents. These were: 551 (55%) residents of supported housing, residential care or nursing homes; 235 (23%) patients with chronic pain; 127 (13%) inpatients on a neurology ward following a stroke; and 89 (9%) patients suffering from Parkinson's disease.


RESULTS
Of the 170 items, 115 were judged to be clinically relevant. Of these 115 items, 77 were retained in the item bank following the item response theory analysis. Of the 38 items that were excluded from the item bank, 24 had either been presented to fewer than 200 respondents or had fewer than 10% or more than 90% of responses in the category 'can carry out'. A further 11 items had different measurement properties for younger and older or for male and female respondents. Finally, 3 items were excluded because the item response theory model did not fit the data.


CONCLUSIONS
The Academic Medical Center linear disability score item bank has promising measurement characteristics for the mixed patient population described in this paper. Further studies will be needed to examine the measurement properties of the item bank in other populations.
Holman
Rebecca
R
Department of Neurology, Academic Medical Center, Amsterdam, The Netherlands. r.holman@amc.uva.nl
Weisscher
Nadine
N
Glas
Cees A W
CA
Dijkgraaf
Marcel G W
MG
Vermeulen
Marinus
M
de Haan
Rob J
RJ
Lindeboom
Robert
R
D000046:Academic Medical Centers; D000203:Activities of Daily Living; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002908:Chronic Disease; D019992:Databases as Topic; D004185:Disability Evaluation; D005260:Female; D006757:Hospital Units; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009426:Netherlands; D009735:Nursing Homes; D017063:Outcome Assessment, Health Care / Q000379:methods* / Q000706:statistics & numerical data; D010146:Pain / Q000188:drug therapy / Q000503:physiopathology; D010300:Parkinson Disease / Q000188:drug therapy / Q000503:physiopathology; D018434:Sickness Impact Profile; D020521:Stroke / Q000503:physiopathology / Q000628:therapy; D011795:Surveys and Questionnaires