Table 2.

Median values of urine creatinine concentration, albumin concentration, and albumin-to-creatinine ratio at baseline, overall and by level of albuminuria

AnalyteMedian (IQR) Values of Fresh SamplesMedian Percentage Change from Samples with no Preservative (IQR)aP Value for Difference between Samples Typesa
PreservativeNo Preservative
All participants
 No. of samplesb9088
 Creatinine, mg/dl74.4 (45.6–111.5)76.9 (47.2–114.3)−2.5% (−3.1% to −1.9%)<0.001
 Albumin, mg/L65.4 (20.3–328.7)62.7 (20.7–289.3)−2.1% (−4.5% to −0.4%)<0.001
 Albumin-to-creatinine ratio, mg/g86.8 (19.5–499.1)90.0 (21.4–479.4)0.7% (−2.0% to 2.3%)0.43
Normo- or microalbuminuria
 No. of samplesb6160
 Creatinine, mg/dl80.7 (53.1–115.6)87.0 (58.3–121.3)−2.6% (−3.0% to −2.0%)<0.001
 Albumin, mg/L27.9 (14.9–69.8)32.5 (14.8–74.7)−2.4% (−4.5% to −0.4%)<0.001
 Albumin-to-creatinine ratio, mg/g33.3 (13.5–92.4)32.9 (13.9–98.0)0.5% (−3.0% to 2.3%)0.74
 No. of samplesb2928
 Creatinine, mg/dl53.6 (36.7–85.0)54.1 (34.8–85.7)−2.3% (−3.3% to −1.5%)<0.001
 Albumin, mg/L553.1 (328.7–973.5)491.0 (289.3–887.1)−1.6% (−3.7% to −0.4%)<0.001
 Albumin-to-creatinine ratio, mg/g857.1 (523.4–1473.4)803.2 (508.3–1391.2)1.3% (−1.6% to 3.2%)0.29
  • IQR, interquartile range.

  • a Among participants with measurements from both preservative and no preservative samples, the percentage change was calculated as the difference in concentration between the sample with preservative and the sample with no preservative divided by the concentration in the sample with no preservative, and it was compared using the Wilcoxon signed rank test (19).

  • b Of the 93 patients in this study with detectable creatinine and albumin, 85 had measurements in both sample types; five only had measurements in samples with preservative, and three only had measurements in samples with no preservative.