Evaluation of the ARCHITECT urine NGAL assay: assay performance, specimen handling requirements and biological variability.
Author(s): Grenier FC, Ali S, Syed H, Workman R, Martens F, Liao M, Wang Y, Wong PY
Publication: Clin Biochem, 2010, Vol. 43, Page 615-20
PubMed ID: 20026020 PubMed Review Paper? No
Purpose of Paper
Conclusion of Paper
Studies
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Study Purpose
The purpose of this study was to determine the effects of storage temperature and duration, freezing method, freeze-thaw cycling, biological variability based on time of collection, specimen pH, and spiking specimens with additional amounts of endogenous substances on NGAL concentrations measured by the ARCHITECT assay in urine. In addition, measurements taken by the ARCHITECT assay were compared with those from the manual ELISA method. Specimens collected for the assessment of biological variability were stored at 2-8 degrees C and assayed within 5 days of collection. Fresh specimens were used immediately after collection for the comparison of the ARCHITECT assay and ELISA methods.
Summary of Findings:
A correlation coefficient of 0.99 demonstrated good agreement between the automated ARCHITECT assay and the manual ELISA method for the determination of NGAL concentration. The ARCHITECT assay was used for all subsequent analysis. Recovery rates of NGAL ranged between 94 and 105% when specimens were spiked with acetone, ascorbic acid, albumin, bilirubin, creatinine, ethanol, glucose, hemoglobin, sodium chloride, oxalic acid, riboflavin, or urea. ARCHITECT assay results were not affected by specimen pH. Refrigerated storage of specimens for up to 22 d had no significant effects on average NGAL concentrations, however concentrations in individual specimens decreased by as much as 19.7% or increased as much as 18.6% after 22 d. NGAL concentrations increased by an average of 7.8% after 13 months of storage at -75 degrees C but decreased by an average of 12% after 13 months of storage at -20 degrees C, and individual specimen variability was much greater among the specimens held at -20 degrees C. Up to 4 freeze-thaw cycles had no significant effect on NGAL concentrations compared to measurements taken after specimens were stored at 4 degrees C for 1 week when freezing was accomplished slowly in a -75 degrees C freezer. However, there was a small but significant average difference of <5% between NGAL concentrations in specimens that were flash frozen during freeze-thaw cycling compared to specimens stored for 1 week at 4 degrees C (p<0.05). The largest biological variation in NGAL concentrations was found between specimens collected at different times on the same day as opposed to between-day or between-individual variation.
Biospecimens
Preservative Types
- None (Fresh)
- Other Preservative
- Frozen
Diagnoses:
- Not specified
- Normal
Platform:
Analyte Technology Platform Protein Clinical chemistry/auto analyzer Protein ELISA Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Clinical chemistry/auto analyzer Specific Technology platform ELISA
Biospecimen Aliquots and Components Biospecimen components Acetone
Ascorbic acid
Albumin
Bilirubin
Creatinine
Ethanol
Glucose
Hemoglobin
Sodium chloride
Oxalic acid
Riboflavin
Urea
Storage Storage temperature 2-8 degrees C
-20 degrees C
-75 degrees C
Biospecimen Preservation Type of fixation/preservation Frozen
None (fresh)
Refrigeration
Storage Storage duration 0 d
1 d
3 d
7 d
15 d
22 d
6 months
13 months
Storage Freeze/thaw cycling 1 cycle
2 cycles
4 cycles
Biospecimen Preservation Cooling or freezing method/ rate Direct transfer to freezer
Ethanol dry ice bath
Biospecimen Acquisition Time of biospecimen collection Multiple times on the same day
Different days within a 2 week period
Biospecimen Aliquots and Components pH 4
5
6
7
8
9