Effects of tobramycin solution for inhalation on global ratings of quality of life in patients with cystic fibrosis and Pseudomonas aeruginosa infection

Abstract

In a previously published placebo-controlled trial, tobramycin solution for inhalation (TSI) was shown to improve lung function and other outcomes in patients with cystic fibrosis (CF). The objectives of the current study were to examine the effects of TSI on global ratings of health-related quality of life (HRQOL) by patients (or their parents) and physicians blind to group assignment, and to determine whether any perceived benefits persisted over time. The global ratings of HRQOL in 520 patients with CF and chronic Pseudomonas aeruginosa infection were analyzed retrospectively. Patients were randomly assigned to receive 24 weeks of placebo or treatment with TSI 300 mg b.i.d., both administered in cycles of 28 days on drug (or placebo) followed by 28 days off, for a total of three cycles. After each on-drug cycle, patients or parents, and physicians, were asked to rate whether the patient's condition was better, unchanged, or worse. There was strong agreement between the paired patient/parent and physician global HRQOL ratings across the three cycles. Regression analyses demonstrated that patients in the TSI group were significantly more likely to report improvements in HRQOL than were patients in the placebo group. This effect was found to be both immediate (end of on-drug cycle 1) and delayed (end of subsequent on-drug cycles 2 and 3) (P < 0.05). In addition, change in forced expired volume in 1 sec (FEV(1)) % predicted values was a significant predictor of improvement in HRQOL ratings by patients and parents. After controlling for change in FEV(1) % predicted, physician ratings showed significant improvement only at the end of cycle 1. Finally, controlling for initial lung disease severity, longitudinal growth models revealed that patients on TSI and their physicians reported higher HRQOL ratings than did placebo patients and their physicians across the three cycles; however, the magnitude of this effect decreased over time. Results of this study provided consistent evidence that TSI was associated with improved global ratings of HRQOL completed by both patients or parents, and physicians. Although these results are promising, they are limited by the use of a single-item rating of health. Future studies of the effects of TSI should utilize a well-validated, disease-specific measure of HRQOL.