Clinical Usefulness of Cystatin C for the Estimation of Glomerular Filtration Rate in Type 1 Diabetes
Reproducibility and accuracy compared with standard measures and iohexol clearance
Article Figures & Tables
Figures
- Figure 1—
Bland-Altmann plots illustrating within-subject variability of cystatin C, plasma creatinine concentration, creatinine clearance, Cockcroft-Gault estimation of GFR, and iohexol clearance. The vertical axis represents the difference of two duplicate tests (second minus first). In each case, the ranges of the vertical and horizontal axes are equal. The dotted lines represent 10% deviations above and below the mean value.
- Figure 2—
Scattergram of the reciprocal of cystatin C versus iohexol clearance expressed per 1.73 m2. Each point represents the mean of two duplicate assessments. Open circles represent nondiabetic subjects and solid diamonds represent diabetic subjects. The dashed line represents the unbiased line of equivalence: the estimate of the underlying linear relationship between the two values, calculated as detailed in the text.
Tables
- Table 1—
Baseline characteristics of patients
No diabetes Type 1 diabetes No proteinuria Microalbuminuria Proteinuria Number of subjects 11 10 10 9 Male:female 6:5 5:5 5:5 5:4 Age (years) 43 ± 11 46 ± 13 60 ± 10 54 ± 15 Duration of diabetes (years) — 24 ± 14 28 ± 13 26 ± 13 BMI (kg/m2) 24.3 ± 2.9 25 ± 3 29.4 ± 5.3 27.7 ± 3.5 HbA1c (%) — 7.9 ± 1.2 9.1 ± 1.6 10.3 ± 1.6 Data are means ± SD.
- Table 2—
Measures of reproducibility
Mean (range) Within-subject SD Between-subject SD Within-subject CV Discriminant ratio (95% CI) Discriminant ratio: P versus iohexol clearance Discriminant ratio: P versus cystatin C Plasma creatinine (μmol/l) 75 (39–131) 7.4 19.0 9.9% 2.5 (1.9–3.2) <0.001 0.065 Creatinine clearance (ml · min · 1.73 m−2) 91 (40–166) 17.6 29.6 19.2% 1.5 (1.1–2.1) <0.001 <0.001 GFR-CG (ml · min · 1.73 m−2) 102 (37–203) 10.1 33.7 9.9% 3.3 (2.5–4.2) <0.001 0.43 Cystatin C (mg/l) 0.98 (0.52–2.03) 0.1 0.3 8.9% 3.4 (2.6–4.4) <0.001 — Iohexol clearance (ml · min · 1.73 m−2) 84 (35–132) 4.7 23.2 5.6% 4.9 (3.9–6.3) — —
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