Evaluation of NGAL TestTM on Cobas 6000

Abstract

Background. Neutrophil Gelatinase-Associated Lipocalin (NGAL) is a promising biomarker for acute kidney injury (AKI). Our objectives were to evaluate the NGAL Test^TM from Bioporto for both urine NGAL and plasma NGAL on the Cobas 6000 c501 (Roche Diagnostics, Rotkreuz, Switzerland) with matched measurements run on Hitachi 917, the method's linearity on the Cobas 6000 in urine, EDTA and Lithium-Heparin (Li-Hep), the influence of using EDTA or Li-Hep tubes and, finally, the impact of freezing and thawing on the sample. Methods. Forty matched samples of Li-Hep and EDTA plasma and 40 urine samples were analyzed for method, anticoagulant, and freeze-thaw comparisons. Linearity was assessed using high NGAL samples diluted in urine, EDTA, and Li-Hep plasma. Commercial internal controls were used for the imprecision study. Results. The Cobas 6000 measured identically with the Hitachi 917, however, not in EDTA plasma (Median_Difference = 17.50 μg/L, p < 0.0001). Freeze-thaw process reduced NGAL ((EDTA: Mean_{Difference =} = 15.13 μg/L, p = 0.0014)(Li-Hep: Median_{Difference =} = 6.5 μg/L, p = 0.0129)). NGAL results were higher in Li-Hep plasma than in EDTA plasma ((Non-thawed: Median_{Difference =} = 14.5 μg/L, p < 0.0001), (Thawed: Median_{Difference =} = 21.5 μg/L, p = 0.0003)). Linearity agreements were observed in all three specimens. Imprecision (CV%) was below 3%. Conclusion. The NGAL Test^TM can be applied on the Cobas 6000 with acceptable performance, although the Cobas 6000 measured higher than the Hitachi 917 in EDTA plasma. Though clinically insignificant, we found that the freeze-thaw process had a reduced effect. NGAL results were higher in Li-Hep tubes than in EDTA tubes. Thus, for blood samples we recommend use of EDTA tubes for NGAL measurements.

Key Words::

• Acute kidney injury
• analytical performance
• immunoassay
• kidney diseases
• NGAL protein
• human
• specimen collection
• specimen handling

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

All reagents, calibrators and controls were provided by BioPorto Diagnostics. For the laboratory work, the laboratory technician's salary was funded by BioPorto Diagnostics.