Table 2A.
Stability of urinary biomarkersa
| Collection and Processing | Mean Percentage Difference (95% confidence interval of mean % difference) when Compared to Immediate Storage at −80°C
|
||
|---|---|---|---|
| KIM-1, n = 6 | NAG, n = 6 | NGAL, n = 6 | |
| Remain at RMb for 2 h, then storage at −80°C | −0.26 (−5.52 to 5.01) | 0.05 (−3.09 to 3.20) | −2.45 (−6.54 to 1.64) |
| Remain at RM for 4 h, then storage at −80°C | 1.43 (−5.39 to 8.25) | 0.48 (−3.19 to 4.15) | −5.3 (−14.89 to 4.30) |
| Remain at RM for 6 h, then storage at −80°C | −3.97 (−10.80 to 2.86) | 0.48 (−2.42 to 3.38) | 2.54 (−7.86 to 12.93) |
| Remain at RM for 24 h, then storage at −80°C | −6.52 (−11.73 to −1.30) | −0.43 (−1.46 to 0.60) | −9.78 (−22.55 to 3.00) |
| Remain at 4°C for 2 h, then storage at −80°C | 1.25 (−4.98 to 7.48) | 0.04 (−4.10 to 4.17) | −3.97 (−9.91 to 3.77) |
| Remain at 4°C for 4 h, then storage at −80°C | 0.43 (−5.37 to 6.23) | 2.38 (−1.75 to 6.51) | 6.65 (0.46 to 12.84) |
| Remain at 4°C for 6 h, then storage at −80°C | 0.16 (−5.61 to 5.92) | 2.07 (−0.69 to 4.83) | −5.19 (−13.47 to 3.09) |
| Remain at 4°C for 24 h, then storage at −80°C | −2.33 (−7.94 to 3.27) | 2.26 (−1.90 to 6.42) | −1.01 (−14.52 to 12.5) |
| Protease inhibitor versus no protease inhibitor | 1.23 (−3.76 to 6.23) | −0.21 (−4.53 to 4.11) | −1.51 (−7.23 to 4.20) |
| Prolonged storage at −80°C | |||
| 1 yr with 3 repeat freeze and thaw cycles | −0.53 (−8.57 to 7.50) | 4.96 (1.51 to 8.41) | −2.43 (−13.53 to 8.66) |
| 2 yr with 3 repeat freeze and thaw cycles | NA | 2.13 (−4.47 to 8.72) | NA |
a
Immediate storage at −80°C and place urine samples at −80°C within first 20 min after initial collection.
b
RM, room temperature; NA, not applicable.