A population based study on the intra and inter-rater reliability of the clock drawing test in Brazil: the Bambuí Health and Ageing Study.
BACKGROUND
Reliability should be considered when selecting a scoring system since it influences validity. CDT reliability has rarely been assessed in population based studies and in developing countries. The aim of the present study was to determine intra and inter-rater reliabilities of the CDT scored by the Shulman (2000) method, in elderly with very low formal educational level from Brazil.


METHODS
CDTs performed by a random sample of 202 subjects of a population-based cohort of elderly were scored on two occasions by the same rater and by two independent raters. Reliability was measured using the kappa statistic, weighted kappa and the intraclass correlation coefficient. Data were stratified according to gender, age and schooling level.


RESULTS
Intra and inter-rater reliabilities were excellent when CDTs were classified as 'normal' (scores 4 or 5) or 'abnormal' (scores 0 to 3) (kappa = 0.99 and 0.94, respectively) and were in the good to excellent range when scored from 0 to 5 (kappa = 0.88 and 0.74, respectively). Difficulties in distinguishing between scores 4 and 5, and a low proportion of score 1 tests were found.


CONCLUSIONS
The CDT scored by the Shulman (2000) method appears to have good to excellent reliability in an elderly population with very low formal educational level. However, difficulties in distinguishing between scores 4 and 5, and a low proportion of score 1 tests suggest these scores may not be totally adequate for this population. Further studies are necessary to determine the consistency of our results in similar populations.
Fuzikawa
Cíntia
C
Public Health and Ageing Research Group (PHARG), Federal University of Minas Gerais Medical School and Oswaldo Cruz Foundation, René Rachou Research Institute, Belo Horizonte, Brazil. cintia@task.com.br
Lima-Costa
Maria Fernanda
MF
Uchoa
Elizabeth
E
Barreto
Sandhi Maria
SM
Shulman
Ken
K
D000368:Aged; D000369:Aged, 80 and over; D001938:Brazil; D015331:Cohort Studies; D004522:Educational Status; D005260:Female; D015577:Geriatric Assessment / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009483:Neuropsychological Tests / Q000592:standards*; D015588:Observer Variation; D010364:Pattern Recognition, Visual / Q000502:physiology*; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity