Development and validation of a new short and simple measure of physical function for juvenile idiopathic arthritis.
OBJECTIVE
To develop and validate a new short and simple measure of physical function in children with juvenile idiopathic arthritis (JIA).


METHODS
The Juvenile Arthritis Functionality Scale (JAFS) is a 15-item questionnaire that explores physical function in 3 body areas (lower limbs, hand/wrist, and upper segment). Validation of the Italian version of the instrument was accomplished by evaluating 211 consecutive JIA patients ages 2.2-18 years. The instrument's feasibility, face and content validity, construct and discriminative ability, internal consistency, interrater reliability, and responsiveness to clinical change were examined. JAFS psychometric properties were compared with those of the Childhood Health Assessment Questionnaire (C-HAQ).


RESULTS
The JAFS was found to be feasible and to possess both face and content validity. The JAFS score correlated with most of the other JIA outcome measures in the range predicted, thereby demonstrating good construct validity, and discriminated well among different levels of disability. The internal consistency (Cronbach's alpha) was 0.82. The intraclass correlation coefficients between raters (mothers, fathers, and children) and between reported and observed level of function ranged from 0.65 to 0.84. The JAFS revealed fair responsiveness, with a standardized response mean ranging from 0.42 to 0.56. Comparison with the C-HAQ indicated that the JAFS may be superior in terms of construct validity and reliability, and at least as good in terms of discriminant validity and responsiveness.


CONCLUSIONS
The JAFS exhibited good reliability, construct validity, and discriminative ability and fair responsiveness, and is therefore a valid instrument for the assessment of physical function in children with JIA.
Istituto di Ricovero e Cura a Carattere Scientifico G. Gaslini, Genoa, Italy.
Giovanni
G
Filocamo
Flavio
F
Sztajnbok
Adriana
A
Cespedes-Cruz
Silvia
S
Magni-Manzoni
Angela
A
Pistorio
Stefania
S
Viola
Nicolino
N
Ruperto
Antonella
A
Buoncompagni
Anna
A
Loy
Alberto
A
Martini
Angelo
A
Ravelli
D000203:Activities of Daily Living; D000293:Adolescent; D001171:Arthritis, Juvenile / Q000150:complications / Q000503:physiopathology*; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D004185:Disability Evaluation; D017079:Exercise Tolerance; D005260:Female; D006304:Health Status; D006801:Humans; D007558:Italy; D008297:Male; D010865:Pilot Projects; D015203:Reproducibility of Results