Table 2.

Cross-sectional correlations of eGFR and creatinine clearance with measured GFR evaluated using 2592 sets of measurements among 1334 participants

VariableiGFRCreatinine ClearanceeGFRCreGFRCyseGFRCr+Cys
Summary statistics
 Mean (SD), ml/min per 1.73 m2122.7 (21.0)121.9 (26.9)119.3 (13.0)113.6 (15.8)117.6 (14.1)
 Median (quartile 1, quartile 3),  ml/min per 1.73 m2121.5 (109.8, 134.0)119.0 (106.0, 134.0)119.6 (112.1, 127.3)116.4 (105.7, 124.1)118.4 (109.2, 126.7)
Comparisons with iGFR
 Pearson r0.360.380.400.47
 Spearman r0.420.390.420.48
 Median difference  (ml/min per 1.73 m2)1.12.67.44.3
 Median percent difference0.92.26.13.5
 IQR of the difference  (ml/min per 1.73 m2)27.222.923.721.7
 IQR of the percent difference22.818.418.617.5
 P30 (%)87.895.093.296.0
 P20 (%)73.682.579.685.3
  • The median difference between iGFR and creatinine clearance or eGFR was calculated on the natural and relative scales as measures of bias, with lower values reflecting lower bias. The IQR of the difference between iGFR and creatinine clearance or eGFR was calculated on the natural and relative scales as measures of precision, with lower values reflecting greater precision. The proportion of participants with creatinine clearance or eGFR values within 30% or 20% of iGFR (P30 or P20, respectively) were calculated as measures of accuracy, with higher numbers reflecting greater accuracy.