TY - JOUR
T1 - Urine stability studies for novel biomarkers of acute kidney injury
AU - Parikh, Chirag R.
AU - Butrymowicz, Isabel
AU - Yu, Angela
AU - Chinchilli, Vernon M.
AU - Park, Meyeon
AU - Hsu, Chi Yuan
AU - Reeves, W. Brian
AU - Devarajan, Prasad
AU - Kimmel, Paul L.
AU - Siew, Edward D.
AU - Liu, Kathleen D.
N1 - Funding Information:
Support: This study was supported by the supplemental American Recovery and Reinvestment Act funds and research grants U01-DK082223, U01-DK082185, U01DK082192, and U01DK082183 from the NIDDK of the National Institutes of Health (NIH) , US Department of Health and Human Services. This publication was also supported by the National Center for Research Resources and the National Center for Advancing Translational Sciences, NIH, through University of California, San Francisco–Clinical and Translational Science Institute grant UL1 RR024131 . Drs Hsu and Siew are additionally supported by grants K24 DK92291 and 5K23DK088964-02, respectively. The opinions expressed in this article are the authors' own and do not reflect the view of the NIH, the Department of Health and Human Services, or the United States government.
PY - 2014/4
Y1 - 2014/4
N2 - Background The study of novel urinary biomarkers of acute kidney injury has expanded exponentially. Effective interpretation of data and meaningful comparisons between studies require awareness of factors that can adversely affect measurement. We examined how variations in short-term storage and processing might affect the measurement of urine biomarkers. Study Design Cross-sectional prospective. Setting & Participants Hospitalized patients from 2 sites: Yale New Haven Hospital (n = 50) and University of California, San Francisco Medical Center (n = 36). Predictors We tested the impact of 3 urine processing conditions on these biomarkers: (1) centrifugation and storage at 4°C for 48 hours before freezing at -80°C, (2) centrifugation and storage at 25°C for 48 hours before freezing at -80°C, and (3) uncentrifuged samples immediately frozen at -80°C. Outcomes Urine concentrations of 5 biomarkers: neutrophil gelatinase-associated lipocalin (NGAL), interleukin 18 (IL-18), kidney injury molecule 1 (KIM-1), liver-type fatty acid-binding protein (L-FABP), and cystatin C. Measurements We measured urine biomarkers by established enzyme-linked immunosorbent assay methods. Biomarker values were log-transformed, and agreement with a reference standard of immediate centrifugation and storage at -80°C was compared using concordance correlation coefficients (CCCs). Results Neither storing samples at 4°C for 48 hours nor centrifugation had a significant effect on measured levels, with CCCs higher than 0.9 for all biomarkers tested. For samples stored at 25°C for 48 hours, excellent CCC values (>0.9) also were noted between the test sample and the reference standard for NGAL, cystatin C, L-FABP and KIM-1. However, the CCC for IL-18 between samples stored at 25°C for 48 hours and the reference standard was 0.81 (95% CI, 0.66-0.96). Limitations No comparisons to fresh, unfrozen samples; no evaluation of the effect of protease inhibitors. Conclusions All candidate markers tested using the specified assays showed high stability with both short-term storage at 4°C and without centrifugation prior to freezing. For optimal fidelity, urine for IL-18 measurement should not be stored at 25°C before long-term storage or analysis.
AB - Background The study of novel urinary biomarkers of acute kidney injury has expanded exponentially. Effective interpretation of data and meaningful comparisons between studies require awareness of factors that can adversely affect measurement. We examined how variations in short-term storage and processing might affect the measurement of urine biomarkers. Study Design Cross-sectional prospective. Setting & Participants Hospitalized patients from 2 sites: Yale New Haven Hospital (n = 50) and University of California, San Francisco Medical Center (n = 36). Predictors We tested the impact of 3 urine processing conditions on these biomarkers: (1) centrifugation and storage at 4°C for 48 hours before freezing at -80°C, (2) centrifugation and storage at 25°C for 48 hours before freezing at -80°C, and (3) uncentrifuged samples immediately frozen at -80°C. Outcomes Urine concentrations of 5 biomarkers: neutrophil gelatinase-associated lipocalin (NGAL), interleukin 18 (IL-18), kidney injury molecule 1 (KIM-1), liver-type fatty acid-binding protein (L-FABP), and cystatin C. Measurements We measured urine biomarkers by established enzyme-linked immunosorbent assay methods. Biomarker values were log-transformed, and agreement with a reference standard of immediate centrifugation and storage at -80°C was compared using concordance correlation coefficients (CCCs). Results Neither storing samples at 4°C for 48 hours nor centrifugation had a significant effect on measured levels, with CCCs higher than 0.9 for all biomarkers tested. For samples stored at 25°C for 48 hours, excellent CCC values (>0.9) also were noted between the test sample and the reference standard for NGAL, cystatin C, L-FABP and KIM-1. However, the CCC for IL-18 between samples stored at 25°C for 48 hours and the reference standard was 0.81 (95% CI, 0.66-0.96). Limitations No comparisons to fresh, unfrozen samples; no evaluation of the effect of protease inhibitors. Conclusions All candidate markers tested using the specified assays showed high stability with both short-term storage at 4°C and without centrifugation prior to freezing. For optimal fidelity, urine for IL-18 measurement should not be stored at 25°C before long-term storage or analysis.
KW - Proteins
KW - acute kidney injury (AKI)
KW - acute renal failure (ARF)
KW - biospecimen handling
KW - concordance
KW - handling
KW - protein stability
KW - storage
KW - urine biomarker
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U2 - 10.1053/j.ajkd.2013.09.013
DO - 10.1053/j.ajkd.2013.09.013
M3 - Article
C2 - 24200462
AN - SCOPUS:84896988610
SN - 0272-6386
VL - 63
SP - 567
EP - 572
JO - American Journal of Kidney Diseases
JF - American Journal of Kidney Diseases
IS - 4
ER -