BACKGROUND: Cystatin C is a low-molecular-weight protein that is freely filtered by the glomerulus and catabolized after reabsorption by the proximal tubular cells in healthy subjects. Urinary cystatin C is a potential biomarker for tubular damage including acute kidney injury (AKI) in the acute phase when patients are submitted to the intensive care unit. METHODS: The aim of this study was to perform a method validation of urinary analysis of cystatin C by particle-enhanced turbidimetric immunoassay (PETIA) on a high-throughput chemical analyzer. Total assay time was 10 min. The antigen excess, linearity, lower limit of quantification (LoQ), recovery, assay precision, stability, and interference caused by hemoglobin were evaluated. RESULTS: The LoQ was calculated to 0.020 mg/l with a coefficient of variation (CV) ≤ 10%. No hook effect was observed and the assay was linear over the studied interval less than 0.020-0.950 mg/l with a regression of R² = 0.9994. The assay had a recovery between 93-100% and the assay precision had a total CV of less than 3.5%. Cystatin C was stable for 3 days in room temperature and 14 days in +4C. The assay did not show any major interference with hemoglobin at a hemoglobin concentration of 10 g/L. The reference interval for urine cystatin C was less than 0.166 mg/l. CONCLUSION: The urinary cystatin C PETIA showed good precision and performance characteristics including short test turnaround times that are necessary qualifications for a biomarker at a routine laboratory.
BACKGROUND:Cystatin C is a low-molecular-weight protein that is freely filtered by the glomerulus and catabolized after reabsorption by the proximal tubular cells in healthy subjects. Urinary cystatin C is a potential biomarker for tubular damage including acute kidney injury (AKI) in the acute phase when patients are submitted to the intensive care unit. METHODS: The aim of this study was to perform a method validation of urinary analysis of cystatin C by particle-enhanced turbidimetric immunoassay (PETIA) on a high-throughput chemical analyzer. Total assay time was 10 min. The antigen excess, linearity, lower limit of quantification (LoQ), recovery, assay precision, stability, and interference caused by hemoglobin were evaluated. RESULTS: The LoQ was calculated to 0.020 mg/l with a coefficient of variation (CV) ≤ 10%. No hook effect was observed and the assay was linear over the studied interval less than 0.020-0.950 mg/l with a regression of R² = 0.9994. The assay had a recovery between 93-100% and the assay precision had a total CV of less than 3.5%. Cystatin C was stable for 3 days in room temperature and 14 days in +4C. The assay did not show any major interference with hemoglobin at a hemoglobin concentration of 10 g/L. The reference interval for urine cystatin C was less than 0.166 mg/l. CONCLUSION: The urinary cystatin C PETIA showed good precision and performance characteristics including short test turnaround times that are necessary qualifications for a biomarker at a routine laboratory.
Authors: Jochen Metzger; Torsten Kirsch; Eric Schiffer; Perihan Ulger; Ebru Mentes; Korbinian Brand; Eva M Weissinger; Marion Haubitz; Harald Mischak; Stefan Herget-Rosenthal Journal: Kidney Int Date: 2010-09-08 Impact factor: 10.612
Authors: Sean M Bagshaw; Christoph Langenberg; Michael Haase; Li Wan; Clive N May; Rinaldo Bellomo Journal: Intensive Care Med Date: 2007-05-09 Impact factor: 17.440
Authors: Yun Kyung Jeon; Mi Ra Kim; Jung Eun Huh; Ji Young Mok; Sang Heon Song; Sang Soo Kim; Bo Hyun Kim; Soo Hyoung Lee; Yong Ki Kim; In Joo Kim Journal: J Korean Med Sci Date: 2011-01-24 Impact factor: 2.153