Validation of an outcomes instrument for tonsil and adenoid disease.

OBJECTIVE To design and validate a disease-specific health status instrument-the Tonsil and Adenoid Health Status Instrument-for use in children with tonsil and adenoid disease. DESIGN Prospective psychometric and clinimetric instrument validation in 3 stages. SETTINGS A tertiary academic pediatric specialty hospital and a tertiary academic hospital, in 2 different cities. PATIENTS/OTHER PARTICIPANTS: Children with tonsil and adenoid disease presenting for evaluation and treatment (n = 224). INTERVENTION/METHOD: Prospective instrument validation. Stage 1 consisted of initial item testing, reduction, and subscale construction; stage 2, reliability and validity testing, factor analysis, and final item reduction; and stage 3, responsiveness analysis. MAIN OUTCOME MEASURES Test-retest and internal consistency reliability; content, construct, and criterion validity; orthogonal principal components factor analysis; and response sensitivity analysis. RESULTS Factor analysis and item analysis confirmed 6 distinct subscales measuring different constructs (aspects) of disease-specific health status that are affected by tonsil and adenoid disease: eating and swallowing, airway and breathing, infections, health care utilization, cost of care, and behavior. For each subscale, the Tonsil and Adenoid Health Status Instrument demonstrated excellent test-retest reliability (r = 0.72-0.88) and internal consistency reliability (Cronbach alpha = .73-.87). Content validity was ensured during the design process. Construct validity was demonstrated by means of convergent and divergent validity with a global quality-of-life instrument (the Child Health Questionnaire, version PF28). Criterion validity was also satisfactory. Finally, the instrument was appropriately sensitive, with high standardized response means and effect sizes. CONCLUSIONS The Tonsil and Adenoid Health Status Instrument is a valid, reliable, and sensitive instrument with 6 distinct subscales. This instrument has significant utility for outcomes research in children with tonsil and adenoid disease.