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Urine stability studies for novel biomarkers of acute kidney injury.

ABSTRACT: 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.Cross-sectional prospective.Hospitalized patients from 2 sites: Yale New Haven Hospital (n=50) and University of California, San Francisco Medical Center (n=36).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.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.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).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).No comparisons to fresh, unfrozen samples; no evaluation of the effect of protease inhibitors.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.

SUBMITTER: Parikh CR

PROVIDER: S-EPMC3969397 | biostudies-other | 2014 Apr

REPOSITORIES: biostudies-other

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Urine stability studies for novel biomarkers of acute kidney injury.

Parikh Chirag R CR Butrymowicz Isabel I Yu Angela A Chinchilli Vernon M VM Park Meyeon M Hsu Chi-Yuan CY Reeves W Brian WB Devarajan Prasad P Kimmel Paul L PL Siew Edward D ED Liu Kathleen D KD

American journal of kidney diseases : the official journal of the National Kidney Foundation 20131105 4

<h4>Background</h4>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.<h4>Study design</h4>Cross-sectional prospective.<h4>Setting & participants</h4>Hospitalized patients from 2 sites: Yale New Haven Hosp ...[more]

PMID: 24200462

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Project description:The interaction between baseline kidney function and the performance of biomarkers of acute kidney injury (AKI) on the development of AKI is unclear.Post hoc analysis of prospective cohort study.The 1,219 TRIBE-AKI Consortium adult cardiac surgery cohort participants.Unadjusted postoperative urinary biomarkers of AKI measured within 6 hours of surgery.AKI was defined as AKI Network stage 1 (any AKI) or higher, as well as a doubling of serum creatinine level from the preoperative value or the need for post-operative dialysis (severe AKI).Stratified analyses by preoperative estimated glomerular filtration rate (eGFR) ? 60 versus > 60mL/min/1.73m(2).180 (42%) patients with preoperative eGFRs?60mL/min/1.73m(2) developed clinical AKI compared with 246 (31%) of those with eGFRs>60mL/min/1.73m(2) (P<0.001). For log2-transformed biomarker concentrations, there was a significant interaction between any AKI and baseline eGFR for interleukin 18 (P=0.007) and borderline significance for liver-type fatty acid binding protein (P=0.06). For all biomarkers, the adjusted relative risk (RR) point estimates for the risk for any AKI were higher in those with elevated baseline eGFRs compared with those with eGFRs?60mL/min/1.73m(2). However, the difference in magnitude of these risks was low (adjusted RRs were 1.04 [95% CI, 0.99-1.09] and 1.11 [95% CI, 1.07-1.15] for those with preoperative eGFRs?60mL/min/1.73m(2) and those with higher eGFRs, respectively). Although no biomarker displayed an interaction for baseline eGFR and severe AKI, log2-transformed interleukin 18 and kidney injury molecule 1 had significant adjusted RRs for severe AKI in those with and without baseline eGFRs?60mL/min/1.73m(2).Limited numbers of patients with severe AKI and post-operative dialysis.The association between early postoperative AKI urinary biomarkers and AKI is modified by preoperative eGFR. The degree of this modification and its impact on the biomarker-AKI association is small across biomarkers. Our findings suggest that distinct biomarker cutoffs for those with and without a preoperative eGFR?60mL/min/1.73m(2) is not necessary.

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Urine stability studies for novel biomarkers of acute kidney injury.

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Urine stability studies for novel biomarkers of acute kidney injury.

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