Mediation Analysis of Urine Osmolality and Response to Tolvaptan in Autosomal Dominant Polycystic Kidney Disease: A Post Hoc Assessment.

What was studied

This post hoc analysis used a 3-year trial of tolvaptan against placebo. The trial involved autosomal dominant polycystic kidney disease. The team asked if early change in urine osmolality could predict long-term response. They used a causal mediation analysis. It looked at kidney function and kidney volume at month 36. They studied non-Japanese people (948) and Japanese people (138) separately.

What they found

In non-Japanese people, the week 3 change in urine osmolality mattered. It explained part of the tolvaptan effect on kidney function at month 36. This was statistically significant. In the Japanese group, that effect was not significant. But the direct tolvaptan effect on kidney function was significant there. Its direct effect on kidney volume growth was significant in both groups.

What it means for patients

The authors say early change in urine osmolality predicted later kidney function in non-Japanese people. They say the link did not reach significance in the smaller Japanese group. They say tolvaptan had a direct effect on kidney volume growth in both groups.

Why it is not certain yet

This is a post hoc analysis of an earlier trial. The Japanese group had 138 people. The marker worked in one group and not in the other. A mediation analysis shows how an effect may work, not proof.

Source

Mediation Analysis of Urine Osmolality and Response to Tolvaptan in Autosomal Dominant Polycystic Kidney Disease: A Post Hoc Assessment.

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