Table 4.

Bland and Altman analysis for the agreement of technetium-99m–diethylene-triamine penta-acetic acid (99mTc DTPA) GFR and cystatin C estimated GFR (estimated by various cystatin C equations) across different GFR categories (ml/min per 1.73 m2)

BiasSD of BiasRelative Bias (%)Relative SD of Bias (%)95% Limit of Agreement for Relative SD of BiasAccuracy (%) Within
10%30%
Whole group
    equations with serum cystatin C
        Bökenkamp et al.−30.7631.45−23.1831.51−84.95, 38.5819.17%55.83%
        Filler and Lepage−2.7020.522.7120.53−42.94, 37.5237.50%85.42%
        Grubb et al.−38.7059.59−21.0731.48−82.79, 40.6417.92%49.58%
        Zapitelli-CysEq15.7825.6713.9020.88−27.01, 54.8328.75%80.83%
    equations with serum cystatin C and serum creatinine
        Bouvet et al.1.1710.28−3.5316.81−36.48, 29.4127.08%79.58%
        CKiD20.1224.0716.0821.72−26.49, 58.6626.67%78.33%
        Zapitelli-CysCrEq17.4522.4915.7718.78−21.03, 52.5829.58%85.42%
GFR < 60 ml/min per 1.73 m2
    equations with serum cystatin C
        Bökenkamp et al.−14.7913.81−17.7973.35−161.56, 125.9816.13%38.71%
        Filler and Lepage−7.918.18−20.7618.68−57.39, 15.8619.35%58.06%
        Grubb et al.−3.314.862.9236.94−69.48, 75.3316.13%51.61%
        Zapitelli-CysEq−0.027.52−0.7418.85−37.69, 36.2248.39%87.10%
    equations with serum cystatin C and serum creatinine
        Bouvet et al.−14.592.39−38.2018.43−74.33, −2.070.00%32.26%
        CKiD−4.578.08−13.6718.25−49.44, 22.0945.16%77.42%
        Zapitelli-CysCrEq0.837.973.2817.26−30.55, 37.1238.71%96.77%
GFR < 90 ml/min per 1.73 m2
    equations with serum cystatin C
        Bökenkamp et al.−27.8017.85−30.2815.31−60.30, −0.2610.81%39.19%
        Filler and Lepage−6.4913.67−7.5415.08−37.10, 22.0129.73%78.38%
        Grubb et al.−13.0324.10−12.6325.57−62.75, 37.4724.32%59.46%
        Zapitelli-CysEq4.8212.407.4416.13−24.19, 39.0750.00%90.54%
    equations with serum cystatin C and serum creatinine
        Bouvet et al.−11.583.59−23.0917.80−57.98, 11.8018.92%71.62%
        CKiD5.569.777.9013.53−18.62, 34.4345.95%89.19%
        Zapitelli-CysCrEq7.9110.2911.6814.70−17.14, 40.5044.59%94.59%
GFR 90 to 134 ml/min per 1.73 m2
    equations with serum cystatin C
        Bökenkamp et al.−41.9731.25−29.8718.31−65.76, 6.0111.76%47.06%
        Filler and Lepage−8.5024.68−5.7518.77−42.53, 31.0351.76%84.71%
        Grubb et al.−51.1958.57−31.4230.01−90.24, 27.3915.29%40.00%
        Zapitelli-CysEq9.2221.9310.0.3219.54−27.97, 48.6127.06%87.06%
    equations with serum cystatin C and serum creatinine
        Bouvet et al.4.915.244.104.48−4.68, 12.8990.59%100.00%
        CKiD14.6917.9515.0216.80−17.90, 47.9429.41%90.59%
        Zapitelli-CysCrEq10.9720.5611.7318.76−25.03, 48.5030.59%89.41%
GFR ≥135 ml/min per 1.73 m2
    equations with serum cystatin C
        Bökenkamp et al.−26.6937.93−14.4617.63−49.02, 20.1034.57%80.25%
        Filler and Lepage12.6131.209.9618.10−25.52, 45.4429.63%92.59%
        Grubb et al.−52.7773.57−23.8927.90−78.58, 30.7914.81%50.62%
        Zapitelli-CysEq34.5328.2526.7118.61−9.76, 63.1911.11%65.43%
    equations with serum cystatin C and serum creatinine
        Bouvet et al.8.927.006.314.48−2.47, 15.0993.83%100.00%
        CKiD43.0120.1632.9314.993.53, 62.336.17%55.56%
        Zapitelli-CysCrEq35.6921.2426.9815.65−3.69, 57.6614.81%72.84%
GFR ≥150 ml/min per 1.73 m2
    equations with serum cystatin C
        Bökenkamp et al.−24.444.78−11.7719.27−49.55, 26.0136.59%85.37%
        Filler and Lepage17.0237.0212.5619.86−26.38, 51.5029.27%90.24%
        Grubb et al.−61.3189.86−24.6830.09−83.67, 34.3012.20%51.22%
        Zapitelli-CysEq39.8933.5029.0120.43−11.02, 69.064.88%60.98%
    equations with serum cystatin C and serum creatinine
        Bouvet et al.6.339.024.075.26−6.24, 14.4097.56%100.00%
        CKiD49.7521.8135.6615.265.74, 65.572.44%46.34%
        Zapitelli-CysCrEq41.0023.8128.9916.39−3.13, 61.1312.20%70.73%
  • Bias = mean difference between 99mTc DTPA GFR and cystatin C eGFR; relative bias = mean % difference = [100 × (99mTc DTPA GFR − cystatin C eGFR)/99mTc DTPA GFR]; SD of the bias = precision (an increase in the SD of bias means a decrease in the precision); SD of the relative bias = relative precision; accuracy = percentage of cystatin C eGFR values within 10% and 30% of the respective 99mTc DTPA GFR measurements. eGFR, estimated GFR; 99mTc DTPA, technetium-99m–diethylene-triamine penta-acetic acid.