Evaluation of a short form for measuring health-related quality of life among pediatric asthma patients.

BACKGROUND: This study was undertaken to derive and validate a short form parent-completed questionnaire to measure health-related quality of life (HRQL) in pediatric asthma patients.
OBJECTIVE: The objectives of this study were to (1) use stepwise analysis to derive a shorter questionnaire from the original long-form questionnaire and (2) determine the tradeoff in precision between the long- and short-form surveys.
METHODS: One hundred eighty-one pediatric asthma patients were enrolled from 4 sites. A parent of each patient completed a general and an asthma-specific questionnaire during routine office visits from June 1995 to January 1997. The questionnaire included the Child Health Questionnaire Parent Form 50, a general HRQL survey, and a 17-item asthma-specific battery assessing daytime symptoms, nighttime symptoms, and functional limitations. All scales were scored from 0 to 100, with higher scores indicating better HRQL. Analysis of variance models were used to derive short-form scales from the 17-item long-form scales, and the final asthma-specific short-form scale structure was confirmed with use of stepwise regression. Scale reliability was assessed with Cronbach's alpha. Validity of the short-form questionnaire was assessed by comparing mean scale scores according to the level of asthma severity defined by several clinical criteria. Asthma severity was assessed with use of percent predicted FEV(1), frequency and type of symptoms, parent rating of disease severity, physician rating of disease severity, and resource use (emergency department use and hospitalizations). The relative validity of each of the short-form scales was measured by comparing the proportion of variance explained by each of the short-form scales compared with the respective long-form scales.
RESULTS: The 17-item asthma-specific battery was reduced to 8 items, the Integrated Therapeutics Group Child Asthma Short Form. The daytime and nighttime symptom scales for each contain 2 items and the functional limitations scale 4 items. Reliability was greater than 0.70 for each of the short-form scales. The absence of ceiling and floor effects indicates each scale's ability to detect changes at both low and high levels of functioning. Lower (poorer) mean HRQL scores for severe cases compared with mild cases, for all disease severity indicators, demonstrated clinical validity. Relative validity estimates, comparing the proportion of explained variance of the short-form scales with that of the long-form scales, ranged from 0. 85 to 1.20, indicating a similar ability to measure change.
CONCLUSIONS: This study documents the development of a brief, multidimensional, 8-item questionnaire for measuring HRQL in pediatric asthma patients. The brevity of the questionnaire makes it practical for use in practice settings and to monitor patients.