Study objectives: Previous studies with short recall periods have suggested that informed administration (previous responses available) may improve the responsiveness and validity of health-related quality-of-life (HRQL) questionnaires in comparison to blind administration (previous responses unavailable). Informed administration may, however, have less impact in studies with longer recall periods. The objective of this randomized trial was to compare the validity and responsiveness of the blind and informed Chronic Respiratory Questionnaire (CRQ) and the St. George's Respiratory Questionnaire (SGRQ) with a 3-month interval between questionnaire completion.
Study design: We randomized 85 patients to blind or informed administration of the CRQ and SGRQ before and after they underwent a standard respiratory rehabilitation program. Patients also completed other HRQL instruments.
Results: At the follow-up administration, we observed important and statistically significant improvement in all four CRQ domains and three SGRQ domains. The results of blind and informed administration differed little. This was true for both the CRQ and the SGRQ, and for both responsiveness and validity.
Conclusions: In contrast to the improved measurement properties after shorter recall periods, the administration of the informed version after > or = 12 weeks may not result in improvements in responsiveness or validity.