Table 3.
Use of the CKD-EPI Creatinine Equation (2009), CKD-EPI Cystatin C Equation (2012), and CKD-EPI Creatinine–Cystatin C Equations (2012) in the External-Validation Data Set Comprising 1119 Participants.*
| Variable | Estimated GFR | |||
|---|---|---|---|---|
| Overall | <60 | 60–89 | ≥90 | |
| ml/min/1.73 m2 of body-surface area | ||||
| Bias — median difference (95% CI)
| ||||
| Creatinine equation | 3.7 (2.8 to 4.6) | 1.8 (1.1 to 2.5) | 6.6 (3.5 to 9.2) | 11.1 (8.0 to 12.5) |
|
| ||||
| Cystatin C equation | 3.4 (2.3 to 4.4) | 0.4 (−0.5 to 1.4) | 6.0 (4.6 to 8.5) | 8.5 (6.5 to 11.2) |
|
| ||||
| Creatinine–cystatin C equation | 3.9 (3.2 to 4.5) | 1.3 (0.5 to 1.8) | 6.9 (5.0 to 8.9) | 10.6 (9.5 to 12.7) |
|
| ||||
| Average of creatinine and cystatin C† | 3.5 (2.8 to 4.1) | 0.4 (−0.3 to 0.8) | 6.5 (4.6 to 8.4) | 11.9 (9.9 to 13.9) |
|
| ||||
| Precision — IQR of the difference (95% CI)
| ||||
| Creatinine equation | 15.4 (14.3 to 16.5) | 10.0 (8.9 to 11.0) | 19.6 (17.3 to 23.2) | 25.0 (21.6 to 28.1) |
|
| ||||
| Cystatin C equation | 16.4 (14.8 to 17.8) | 11.0 (10.0 to 12.4) | 19.6 (16.1 to 23.1) | 22.6 (18.8 to 26.3) |
|
| ||||
| Creatinine–cystatin C equation | 13.4 (12.3 to 14.5) | 8.1 (7.3 to 9.1) | 15.9 (13.9 to 18.1) | 18.8 (16.8 to 22.5) |
|
| ||||
| Average of creatinine and cystatin C equations† | 13.9 (12.9 to 14.7) | 7.9 (7.1 to 9.0) | 15.8 (13.9 to 17.7) | 18.6 (16.1 to 22.2) |
|
| ||||
| Accuracy — % (95% CI)‡
| ||||
| 1 − P30
| ||||
| Creatinine equation | 12.8 (10.9 to 14.7) | 16.6 (13.6 to 19.7) | 10.2 (6.4 to 14.2) | 7.8 (5.1 to 11.0) |
|
| ||||
| Cystatin C equation | 14.1 (12.2 to 16.2) | 21.4 (18.2 to 24.9) | 12.7 (8.5 to 17.4) | 2.2 (0.6 to 3.9) |
|
| ||||
| Creatinine–cystatin C equation | 8.5 (7.0 to 10.2) | 13.3 (10.7 to 16.1) | 5.3 (2.7 to 8.2) | 2.3 (0.9 to 4.2) |
|
| ||||
| Average of creatinine and cystatin C equations† | 8.2 (6.7 to 9.9) | 12.1 (9.5 to 14.8) | 6.4 (3.6 to 9.7) | 2.9 (1.3 to 4.9) |
|
| ||||
| 1 − P20 | ||||
|
| ||||
| Creatinine equation | 32.9 (30.1 to 35.7) | 37.2 (33.1 to 41.2) | 31.1 (25.1 to 37.4) | 26.5 (21.7 to 31.4) |
|
| ||||
| Cystatin C equation | 33.0 (30.3 to 35.7) | 42.1 (38.2 to 46.1) | 29.3 (23.6 to 35.4) | 19.4 (15.4 to 23.7) |
|
| ||||
| Creatinine–cystatin C equation | 22.8 (20.4 to 25.2) | 28.6 (25.1 to 32.4) | 17.8 (13.3 to 22.9) | 16.2 (12.4 to 20.5) |
|
| ||||
| Average of creatinine and cystatin C equations† | 23.7 (21.3 to 26.1) | 29.1 (25.7 to 32.8) | 17.6 (13.2 to 22.4) | 18.8 (14.6 to 23.2) |
*
The equations are given in Table 2. CI denotes confidence interval, and IQR interquartile range.
†
Averages are for the estimated GFRs from the CKD-EPI creatinine equation3 alone and the CKD-EPI cystatin C equation alone.
‡
Accuracy was calculated as the percentage of estimates that differed from the measured GFR by more than 30% (1 − P30) and the percentage that differed by more than 20% (1 − P20).