Table 3.
Predictive value of eHTKV-α and other variables for annual change in TKV over 3 years
| Variable | Univariate regression model | Multivariate regression model | Multivariate regression model (variable reduction method)a | ||||||
|---|---|---|---|---|---|---|---|---|---|
| St. β (parameter estimate) | 95% CI | P value | St. β (parameter estimate) | 95% CI | P value | St. β (parameter estimate) | 95% CI | P value | |
| Change in eHTKV-α from baseline at 1 year (%) | 0.009 | 0.008, 0.009 | < 0.001 | 0.007 | 0.007, 0.008 | < 0.001 | 0.009 | 0.008, 0.009 | < 0.001 |
| Change in eGFR from week 3 at 1 year (%) | − 0.000 | − 0.001, − 0.000 | 0.008 | 0.000 | − 0.000, 0.000 | 0.7 | – | – | – |
| Change in plasma copeptin from baseline at week 3 (pmol/l) | − 0.000 | − 0.000, 0.000 | 0.4 | 0.000 | 0.000, 0.000 | 0.02 | – | – | – |
| Change in urine osmolality from baseline at week 3 (mOsm/kg) | − 0.000 | − 0.000, 0.000 | 0.4 | − 0.000 | − 0.000, 0.000 | 0.2 | – | – | – |
| Mean tolvaptan dose (mg/day) | 0.000 | − 0.000, 0.000 | 0.4 | 0.000 | − 0.000, 0.000 | 0.9 | – | – | – |
| Male vs. female sex | 0.031 | 0.024, 0.039 | < 0.001 | 0.013 | 0.007, 0.020 | < 0.001 | 0.010 | 0.004, 0.016 | 0.001 |
| Age (years) | − 0.002 | − 0.002, − 0.001 | < 0.001 | − 0.001 | − 0.002, − 0.001 | < 0.001 | − 0.002 | − 0.002, − 0.001 | < 0.001 |
| White vs. Asian/other race | 0.007 | − 0.004, 0.017 | 0.2 | 0.008 | − 0.001, 0.016 | 0.07 | – | – | – |
| Baseline eGFR (ml/min per 1.73 m2) | − 0.000 | − 0.000, 0.000 | 0.4 | − 0.000 | − 0.000, 0.000 | 0.6 | – | – | – |
| Baseline systolic BP (mmHg) | 0.000 | − 0.000, 0.001 | 0.07 | − 0.000 | − 0.000, 0.000 | 0.9 | – | – | – |
| Baseline BMI (kg/m2) | 0.002 | 0.002, 0.003 | < 0.001 | 0.001 | 0.000, 0.002 | 0.002 | 0.001 | 0.001, 0.002 | < 0.001 |
| Baseline log10 TKV (ml)b | 0.044 | 0.025, 0.064 | < 0.001 | − 0.007 | − 0.026, 0.011 | 0.4 | – | – | – |
| Baseline log10 copeptin (pmol/l)b | 0.015 | 0.002, 0.029 | 0.02 | 0.000 | − 0.010, 0.011 | 0.9 | – | – | – |
| Baseline urine osmolality (mOsm/kg) | − 0.000 | − 0.000, 0.000 | 0.7 | − 0.000 | − 0.000, 0.000 | 0.6 | – | – | – |
| R2 | – | – | – | 0.526c | – | – | 0.535c | – | – |
Regression analyses included tolvaptan-assigned patients in TEMPO 3:4 with TKV data available to calculate eHTKV-α at baseline and 1 (n = 812); statistically significant values are indicated in bold. Annual change in TKV (left and right kidneys) was calculated as the slope of a regression model over time on TKV values obtained at baseline, and years 1, 2 and 3
BMI, body mass index; BP, blood pressure; CI, confidence interval; eGFR, estimated glomerular filtration rate; eHTKV-α, estimated height-adjusted total kidney volume growth rate; R2, coefficient of determination; St. β, standardised regression coefficient; TKV, total kidney volume
aBackward stepwise selection was applied as the variable reduction method
bLog transformation was applied because baseline TKV and copeptin data are not normally distributed
cR2 represents the extent to which the variance of the dependent variables accounts for the variance of independent variables in a regression model