EQ-5D Scores In Patients Receiving Tolvaptan for the Treatment Of Hyponatraemia Secondary to the Syndrome of Inappropriate Antidiuretic Hormone Secretion.

Abstract

Hyponatraemia (HN) is estimated to occur in 15% of all hospitalised patients with syndrome of inappropriate antidiuretic hormone secretion (SIADH) being one of the most common aetiologies. Patients treated with tolvaptan have demonstrated improvements in health related quality of life (HRQL) in the SALT I & II randomised controlled trials. The objective of this study was to map the SF-12 responses from SALT I & II to EQ-5D using a publically available algorithm and predict the change in EQ-5D associated with tolvaptan. SF-12 scores from the pooled SALT I & II studies were converted to EQ-5D scores using a mapping algorithm developed by Gray, et. al 2006. Simulated EQ-5D scores were then used to estimate changes in EQ-5D from baseline at day 30 using ordinary least squares regression (OLS) as a function of baseline characteristics, treatment arm and achievement of sodium correction (NA+) at day 4 (>135 mmol/l). A preferred model was selected based on the highest adjusted R-squared. Secondary analyses looked at change from baseline in EQ-5D at day 7, day 14 and at 7 day follow-up following treatment discontinuation. The preferred model included baseline age, gender, sodium level, EQ-5D and a tolvaptan indicator variable. Based on this model, tolvaptan was associated with a positive increase in simulated EQ-5D of 0.10 (n=164, p=0.03) at day 30 vs. placebo. After 7 days follow-up, tolvaptan was associated with a positive, but non- statistically significant effect of 0.04 (n=74, p=0.54). No effect was observed at day 7 (n=76, p=0.90) or at day 14 (n=85, p=0.84). Sodium correction did not appear to be a statistically significant predictor of HRQL. The preferred model indicated a statistically significant improvement in HRQL associated with tolvaptan use at day 30. Further research is required to establish whether sodium correction has an effect of HRQL.