The clinical meaning of functional outcome scores in children with juvenile arthritis

The Childhood Health Assessment Questionnaire (CHAQ) is the most widely used measure of function in childhood arthritis and yields a score of 0 (no disability) to 3 (very severe disability). This study ascertained the cutoff levels for CHAQ scores that represent no, mild, moderate, and severe disability, to determine the minimal clinically important change in scores and to determine whether the minimal important change in scores is similar for parent-reported assessments and the self-assessments provided by their older children.

One hundred thirty-six parents of children with arthritis were interviewed. They were asked to complete the CHAQ by assessing their child's functional status under 3 categories: current health, a hypothetical small improvement, and a hypothetical small worsening. They also completed a categorical scale of subjective disability. Those children who were > or = 10 years old also completed the CHAQ interview separately.

The pediatric patients had mostly no, mild, or moderate disability. For those children rated as having no disability, the median CHAQ score was 0. The median CHAQ scores corresponding to mild, mild-to-moderate, and moderate disability were 0.13, 0.63, and 1.75, respectively. The minimal clinically important improvement was a reduction in score of 0.13. The minimal clinically important deterioration was a median change in score of 0.75. This discrepancy may be due to the ceiling effect seen with the CHAQ. There were no significant differences when the children assessed themselves.

Clinicians, as well as researchers setting protocols, should aim for a mimimum improvement of 0.13 in the CHAQ score when treating pediatric patients with arthritis.