CORRELATION BETWEEN CONVENTIONAL DISEASE-ACTIVITY MEASURES IN JUVENILE CHRONIC ARTHRITIS

Objective - To estimate in a cross sectional analysis the degree of co linearity among the disease activity measures more commonly used in ju venile chronic arthritis (JCA). Methods - This study assessed in a sin gle clinical evaluation three subjective variables, three measures of functional capacity, eight articular indices, and two laboratory indic ators of systemic inflammation in 55 consecutive children with JCA. Th e relation between the clinical measures of JCA activity was determine d by Pearson correlation coefficients. An r value of 0.7 or greater wa s considered evidence of colinearity. Results - Among the subjective v ariables, parent global assessment of overall well being and parent as sessment of pain were correlated with each other; the physician assess ment of disease activity did not show evidence of colinearity with any other variable. The functional status measures were correlated with e ach other, but not with the indices of articular inflammation. There w as a high degree of colinearity among the articular variables, with th e number of active joints and the overall severity score being correla ted with each other as well as with all the single articular indices. The laboratory variables were correlated with each other, but not with any of the articular, functional or subjective variables. Conclusion - Our results show a high degree of colinearity among the disease acti vity measures belonging to the same category, whereas this is uncommon for variables that investigate different domains of disease activity. These data underline the need to include the evaluation of each domai n in the assessment of JCA activity.