The  Childhood Health Assessment Question naire ( C-HAQ )  was the most extensively studied instrument and had high reliability , but only moderate correlations with other indices of disease activity and poor responsiveness to change in disease status .
The physician global assessment of disease activity ( PGA ) and articular indices had the strongest association with disease activity and were the most responsive to change .
Measures of psychosocial function and quality of life were moderately associated with measures of disease activity , but were less responsive to changes in disease status .
In children with JIA , no single instrument was superior in reliability or validity or in describing the impact of JIA .
Although the C-HAQ has been extensively evaluated , the PGA and articular indices appear to have the highest responsiveness to change and , therefore , the highest potential for detecting important differences in treatment response
OBJECTIVE To review the performance characteristics of the instruments most commonly used to measure clinical outcomes in juvenile idiopathic arthritis ( JIA ) , including global assessment s , articular indices , functional/disability assessment s , and quality of life measures .
METHODS As part of an Agency for Healthcare Research and Quality comparative effectiveness review of antirheumatic drugs , we explored the characteristics of commonly used outcome measures for JIA .
The Visual Analogue WOMAC 3.0 scale - internal validity and responsiveness of the VAS version
Background Many people suffer with Osteoarthritis ( OA ) and subsequent morbidity . Therefore , measuring outcome associated with OA is important . The Western Ontario and McMaster Universities Osteoarthritis Index ( WOMAC ) has been a widely used patient reported outcome in OA . However , there is relatively little evidence to support the use of the Visual Analogue Scale ( VAS ) version of the scale . We aim ed to explore the internal validity and responsiveness of this VAS version of the WOMAC . Methods Patients with chronic hip or knee pain of mechanical origin , waiting for a hip or knee joint replacement completed the WOMAC as part of a study to investigate the effects of acupuncture and placebo controls . Validity was tested using factor analysis and Rasch analysis , and responsiveness using st and ardised response means . Results Two hundred and twenty one patients ( mean age 66.8 , SD 8.29 , 58 % female ) were recruited . Factor and Rasch analysis confirmed unidimensional Pain and Physical Functioning scales , capable of transformation to interval scaling and invariant over time . Some Differential Item Functioning ( DIF ) was observed , but this cancelled out at the test level . The Stiffness scale fitted the Rasch model but adjustments for DIF could not be made due to the shortness of the scale . Using the interval transformed data , St and ardised Response Means were smaller than when using the raw , ordinal data . Conclusions The WOMAC Pain and Physical Functioning subscales satisfied unidimensionality and ordinal scaling tests , and the ability to transform to an interval scale . Some Differential Item Functioning was observed , but this cancelled out at the test level and , by doing so , at the same time removed the disturbance of unidimensionality . The scaling characteristics of sets of items which use VAS require further analysis , as it would appear that they can lead to spurious levels of responsiveness and scale compression because they exaggerate the distortion of the ordinal scale . Trial numberUKCRN study ID : 4881IS RCT
The  Childhood Health Assessment Question naire ( C-HAQ )  was the most extensively studied instrument and had high reliability , but only moderate correlations with other indices of disease activity and poor responsiveness to change in disease status .
The physician global assessment of disease activity ( PGA ) and articular indices had the strongest association with disease activity and were the most responsive to change .
Measures of psychosocial function and quality of life were moderately associated with measures of disease activity , but were less responsive to changes in disease status .
In children with JIA , no single instrument was superior in reliability or validity or in describing the impact of JIA .
Although the C-HAQ has been extensively evaluated , the PGA and articular indices appear to have the highest responsiveness to change and , therefore , the highest potential for detecting important differences in treatment response
OBJECTIVE To review the performance characteristics of the instruments most commonly used to measure clinical outcomes in juvenile idiopathic arthritis ( JIA ) , including global assessment s , articular indices , functional/disability assessment s , and quality of life measures .
METHODS As part of an Agency for Healthcare Research and Quality comparative effectiveness review of antirheumatic drugs , we explored the characteristics of commonly used outcome measures for JIA .