Table 2:
Application of change in urine protein to predict GFR slope in new RCTs: predicted treatment effect on c inical endpoint and positive predictive values, for 6 months sample_
| GFR Slope | Observed Treatment effect on change in UP | Infinite sized RCT | Modest sized RCT (N=250) | Small sized RCT (N=100) | |||
|---|---|---|---|---|---|---|---|
| Median Treatment effect on GFR slope and 95% Prediction Interval | PPV | Median Treatment effect on GFR slope and 95% Prediction Interval | PPV | Median Treatment effect on GFR slope and 95% Prediction Interval | PPV | ||
| Total slope over 3 years | 0.5 | 4.10 (0.34, 7.46) | 0.98 | 4.07 (0.24, 8.01) | 0.98 | 4.01 (0.05, 8.53) | 0.98 |
| 0.6 | 2.77 (−0.49, 5.73) | 0.96 | 2.73 (−0.63, 6.15) | 0.96 | 2.70 (−0.86, 6.69) | 0.94 | |
| 0.7 | 1.61 (−1.26, 4.61) | 0.92 | 1.62 (−1.59, 4.91) | 0.89 | 1.62 (−1.96, 5.35) | 0.85 | |
| 0.8 | 0.61 (−2.13, 3.77) | 0.75 | 0.66 (−2.51, 4.00) | 0.70 | 0.68 (−2.98, 4.30) | 0.67 | |
| Threshold for treatment effect on UP to assure PPV ≥ 95% (90%) | 0.64 (0.72) | 0.62 (0.69) | 0.58 (0.66) | ||||
| Chronic slope | 0.5 | 3.27 (1.08, 5.83) | 0.99 | 3.25 (0.91, 6.36) | 0.99 | 3.19 (0.56, 6.96) | 0.99 |
| 0.6 | 2.06 (0.26, 3.92) | 0.98 | 2.04 (−0.01, 4.56) | 0.97 | 1.99 (−0.47, 5.18) | 0.95 | |
| 0.7 | 1.03 (−0.56, 2.60) | 0.94 | 1.03 (−1.03, 3.16) | 0.88 | 1.02 (−1.57, 3.82) | 0.81 | |
| 0.8 | 0.13 (−1.46, 1.74) | 0.58 | 0.16 (−2.05, 2.18) | 0.57 | 0.17 (−2.62, 2.73) | 0.56 | |
| Threshold for treatment effect on UP to assure PPV ≥ 95% (90%) | 0.69 (0.73) | 0.64 (0.68) | 0.60 (0.65) | ||||
UP, urine protein; PPV, positive predictive value.
Treatment effect on change in urine protein is expressed as geometric mean ratio. This can be converted to percent reduction in urine protein by 1-GMR *100. Treatment effect on GFR slope is expressed as mean difference between treatment arms. Prediction intervals are Bayesian credible intervals. PPV is defined as the probability that the treatment reduces the magnitude of the mean GFR slope by any amount which is greater than 0. The thresholds for the treatment effect on UP, is the change in UP required to assure PPV for a GFR slope > 0 of greater or equal to 95% (90%) modest RCT was defined as having a sample size of 250 (SE 0.09) and a small RCT was defined as having a sample size of 150 (SE 0.09), assuming a standard deviation of 0.75 for change in log urine protein. eTable10 includes the 80% Bayesian credible intervals for the predicted treatment effect on the GFR slope along with the 95% credible intervals shown here. eTable11 includes the threshold for treatment effect on UP to assure PPV ≥ 97.5%, along with the 95% and 90% as shown here.