Table 3.
Effect of different formulas at their recommended time points
| Formula | Mean bias (GFR1p − GFR7p) | Proportion of measures within x% of reference method (95% CI)a | P valuea | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Time (h) | r | Bias | Limits of agreement | P5 | P10 | P15 | P20 | ||||||
| % of measures | 95% CI | % of measures | 95% CI | % of measures | 95% CI | % of measures | 95% CI | ||||||
| GFR1p-Fleming | 2 | 0.99 | − 1.8 | − 12.3 to 8.8 | 54 | 44–64 | 79 | 70–86 | 86 | 78–92 | 90 | 82–94 | 0.42 |
| 3 | 0.98 | − 1.5 | − 13.5 to 10.5 | 56 | 46–66 | 82 | 73–89 | 89 | 81–93 | 91 | 83–95 | N/A | |
| 3.5 | 0.98 | 0.1 | − 12.4 to 12.5 | 44 | 35–54 | 81 | 72–88 | 87 | 79–93 | 89 | 82–94 | 0.51 | |
| 4 | 0.98 | 1.5 | − 12.4 to 15.4 | 41 | 31–51 | 75 | 65–83 | 90 | 82–94 | 92 | 84–96 | 0.10 | |
| GFR1p-Ham&Piepz | 2 | 0.98 | 4.1 | − 11.0 to 19.2 | 42 | 32–52 | 64 | 54–72 | 73 | 63–81 | 76 | 67–83 | < 0.001 |
| GFR1p-Groth&Aasted | 2 | 0.98 | 3.6 | − 9.2 to 16.3 | 35 | 27–45 | 65 | 55–73 | 75 | 65–83 | 81 | 72–88 | < 0.001 |
| GFR1p-Stake | 3 | 0.97 | 5.8 | − 16.2 to 27.8 | 33 | 25–3 | 66 | 56–74 | 78 | 69–85 | 82 | 73–89) | 0.002 |
| GFR1p-Jacobsson | 2 | 0.97 | − 1.6 | − 26.0 to 22.8 | 32 | 24–42 | 58 | 48–68 | 69 | 59–77 | 78 | 69–85 | < .001 |
| 3 | 0.98 | 1.0 | − 17.7 to 19.7 | 34 | 26–44 | 58 | 48–68 | 74 | 64–82 | 81 | 72–88 | < .001 | |
| 3.5 | 0.98 | 2.2 | − 14.6 to 19.0 | 27 | 19–37 | 64 | 54–73 | 75 | 65–82 | 82 | 73–89 | < .001 | |
| 4 | 0.98 | 2.6 | − 14.6 to 19.8 | 32 | 24–42 | 65 | 55–73 | 76 | 67–83 | 88 | 79–93 | < .001 | |
| 5 | 0.98 | 1.9 | − 12.5 to 16.3 | 43 | 33–53 | 72 | 62–80 | 85 | 77–91 | 91 | 83–95 | 0.04 | |
| GFR1p-Jacobsson-mod. | 2 | 0.97 | − 0.5 | − 24.3 to 23.2 | 33 | 25–43 | 61 | 51–71 | 70 | 60–78 | 78 | 69–85 | < 0.001 |
| 3 | 0.98 | 0.2 | − 16.7 to 17.1 | 35 | 27–45 | 69 | 59–77 | 75 | 65–83 | 84 | 76–90 | 0.003 | |
| 3.5 | 0.98 | 0.8 | − 14.1 to 15.7 | 41 | 32–51 | 65 | 55–74 | 80 | 71–87 | 88 | 80–93 | < 0.001 | |
| 4 | 0.98 | 0.8 | − 14.5 to 16.1 | 42 | 32–52 | 71 | 61–79 | 85 | 77–91 | 91 | 83–95 | 0.02 | |
| 5 | 0.98 | − 0.4 | − 13.8 to 13.0 | 50 | 40–60 | 74 | 64–82 | 90 | 82–94 | 94 | 87–97 | 0.08 | |
| GFR2p-JBM | 2 and 5 | 0.99 | − 1.7 | − 9.4 to 6.1 | 73 | 63–81 | 97 | 97–99 | 100 | 96–100 | 100 | 96–100 | < 0.001 |
Evaluation of optimal time for blood sampling was investigated using five different sampling time points after iohexol injection, namely 2, 3, 3.5, 4 and 5 h. glomerular filtration rate (GFR) (mL/min/1.73m2) was estimated by one-point methods at time points recommended in the original publications (n = 96 for all time points except for 3.5 h, where n = 95) and by the reference method (GFR7p). Mean bias, 95% limits of agreement and correlation (r) with reference method are shown calculated. For comparison the two-point method of Jødal Brøchner Mortensen (GFR2p-JBM) was added
N/A, Not applicable
aEstimated accuracy is shown as P5, P10, P15 and P20, namely, the percentage of patients within ± 5, 10, 15 and 20% of the reference method, respectively, along with 95% confidence intervals (CI)
bComparison with Fleming P10 at 3 h