Long-term Stability of Urinary Biomarkers of Acute Kidney Injury in Children.
Author(s): Schuh MP, Nehus E, Ma Q, Haffner C, Bennett M, Krawczeski CD, Devarajan P
Publication: Am J Kidney Dis, 2016, Vol. 67, Page 56-61
PubMed ID: 26032628 PubMed Review Paper? No
Purpose of Paper
This paper investigated the effects of short-term storage temperature, freeze-thaw cycling and long-term storage at -80˚C on levels of neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule 1 (KIM-1), and interleukin 18 (IL-18) in urine from children with or without acute kidney injury (AKI).
Conclusion of Paper
NGAL, KIM-1, and IL-18 levels decreased significantly when urine was stored at 25˚C for 24 h before analysis but were unaffected by 24 h of storage at -80 or 4˚C. KIM-1, NGAL, and IL-18 levels declined slightly with freeze-thaw cycling with significant declines from baseline in KIM-1 and IL-18 first observed after a single cycle and in NGAL after 2 cycles. Compared to baseline, urine stored at -80˚C had significantly lower levels of KIM-1 and IL-18 after 3 years and NGAL after 5 years. The findings were similar when only patients with or without AKI were considered but significant at three years, depending on AKI and biomarker.
Studies
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Study Purpose
This study investigated the effects of short-term storage temperature, freeze-thaw cycling, and long-term storage at -80˚C on levels of NGAL, KIM-1, and IL-18 in urine from children with or without AKI obtained after cardiac bypass surgery. Urine was collected by an unspecified method from 40 children with AKI and 40 children without AKI 2 to 6 hours after cardiac bypass surgery. Immediately following collection, urine was centrifuged and the supernatant was aliquoted. Aliquots of urine from 10 patients with AKI and 10 patients without were analyzed immediately; after 24 h of storage at -80, 4, and 25˚C; and after one, two, and three freeze (-80˚C)-thaw (unspecified method) cycles. Aliquots of urine from 60 patients (30 with AKI, 30 without AKI) were analyzed immediately and again after 3 months and 5 years at -80˚C. Levels of NGAL, KIM-1, and IL-18 were determined by ELISA.
Summary of Findings:
NGAL, KIM-1, and IL-18 levels decreased 5.6%, 6.1%, and 10.1%, respectively when urine was stored at 25˚C for 24 h before analysis (P<0.05) but were unaffected by 24 h of storage at -80 or 4˚C. KIM-1, NGAL, and IL-18 levels declined progressively with increased freeze-thaw cycles, with significant declines from baseline in KIM-1 and IL-18 first observed after a single cycle (P<0.05), and in NGAL after two cycles (P<0.05). However, even after three cycles the declines were limited to 3% from baseline. Significant declines in KIM-1 and IL-18 compared to baseline were found after three years or more of storage at -80˚C (-0.38% and -1.31%, respectively, P<0.05, both) and a significant 0.84% decline in NGAL was found after five years (P<0.05). The findings were similar when only urine from patients with AKI were considered but the decrease in IL-18 was not significant until five years of storage. When only urine from patients without AKI were considered, the difference in KIM-1 levels were not significant after three years but the difference in IL-18 after three years was significant.
Biospecimens
Preservative Types
- Frozen
- None (Fresh)
Diagnoses:
- Other diagnoses
- Cardiovascular Disease
Platform:
Analyte Technology Platform Protein ELISA Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Preaquisition Diagnosis/ patient condition Acute kidney injury
No acute kidney injury
Storage Storage temperature -80˚C
4˚C
25˚C
ELISA Specific Targeted peptide/protein NGAL
KIM-1
IL-18
Storage Freeze/thaw cycling 0 cycles
1 cycle
2 cycles
3 cycles
Biospecimen Preservation Type of fixation/preservation None (fresh)
Frozen
Storage Storage duration 0 h
24 h
3 years
5 years