Original Articles
Internal Consistency and Validity of the Spanish Version of the St. George' Respiratory Questionnaire for Use in Patients With Clinically Stable Bronchiectasis

https://doi.org/10.1016/S1579-2129(06)60410-2Get rights and content

Objective

To analyze the reliability and validity of the St. George's Respiratory Questionnaire (SGRQ) for use in patients with clinically stable bronchiectasis.

Material and Methods

The SGRQ (50 items on 3 scales—symptoms, activity, and impact) was administered to 102 patients (mean [SD] age, 69.5 [8.7] years; 63% men) with clinically stable bronchiectasis. Disease severity was classified according parameters such as airflow obstruction (forced expiratory volume in 1 second), colonization by Pseudomonas aeruginosa, extent of bronchiectasis, symptoms, daily quantity of sputum, and number of exacerbations. Internal consistency (Cronbach's alpha and correlation between items and between item and scale), concurrent validity (correlation between items and clinical variables), predictive validity (correlation between items and severity), and construct validity (factorial analysis of main components) were assessed.

Results

The internal consistency of the SGRQ was excellent (Cronbach's alpha between 0.81 and 0.87 for the different scales, and 0.90 for the overall score). Concurrent validity was high, as correlations between items and clinical variables were significant and followed the expected distribution. The SGRQ differentiated between degrees of disease severity, regardless of the clinical variable used. The factorial analysis showed a construct of 4 factors that were only moderately similar to the original structure of the questionnaire, due mainly to inclusion of a small number of questions with conditioned response and others with low discriminatory capacity.

Conclusions

The SGRQ shows excellent concurrent and predictive internal consistency and validity, though restructuring of the original construct would be advisable before use in patients with stable bronchiectasis.

Objetivo

Analizar la fiabilidad y validez del St. George's Respiratory Questionnaire (SGRQ) para su uso en pacientes afectados de bronquiectasias estables.

Material y Métodos

El SGRQ (50 ítems en 3 escalas: síntomas, actividad e impacto) se administró a 102 pacientes (edad media ± desviación estándar de 69,5 ± 8,7 años; 63% varones) con bronquiectasias clínicamente estables. Se clasificó la gravedad según diferentes parámetros: obstrucción al flujo respiratorio (volumen espiratorio forzado en el primer segundo), colonización por Pseudomonas aeruginosa, extensión de las bronquiectasias, síntomas, cantidad de esputo diario y número de agudizaciones. Se calcularon la consistencia interna (alfa de Cronbach y correlación ítem-ítem e ítems-escala), la validez concurrente (correlación ítems-variables medidas), la validez predictiva (correlación ítems-parámetros de gravedad) y la validez de constructo (análisis factorial de componentes principales).

Resultados

La consistencia interna del SGRQ fue excelente (alfa de Cronbach entre 0,81 y 0,87 para las distintas escalas, y 0,90 para la puntuación total). La validez concurrente fue elevada, ya que las correlaciones ítems-variables medidas fueron significativas y se distribuyeron de la forma prevista. El SGRQ permitió diferenciar adecuadamente los distintos grados de gravedad de la enfermedad independien-temente de los parámetros utilizados. El análisis factorial mostró un constructo de 4 factores que se asemejaba tan solo de forma moderada a la estructura original del cuestionario, sobre todo por la inclusión de preguntas con bajo porcentaje de respuestas obligadas y otras con bajo poder discriminatorio.

Conclusiones

El SGRQ presenta una excelente consistencia interna y validez tanto concurrente como predictiva, si bien sería recomendable una reestructuración previa del constructo original para su uso en pacientes con bronquiectasias estables.

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  • Cited by (0)

    Work subsidized in part by the grant RedRespira-ISCiii-TRIC-03/11.

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