BACKGROUND: Cystatin C is an alternative biomarker for assessing glomerular filtration rate (GFR), yet lack of standardization could hinder its widespread use. In this study we analytically and clinically validated a newer cystatin C particle-enhanced turbidimetric assay (PETIA) traceable to a certified reference material and compared it to the more commonly used particle-enhanced nephelometric assay (PENIA). METHODS: Samples from four patient cohorts at the Mayo Clinic were studied: 1) clinical convenience samples (n=50); 2) samples from patients undergoing iothalamate urinary clearance testing for clinical indications (n=101); 3) volunteers without kidney disease (n=292); 4) samples from 1999-2000 with previous cystatin C measurements. RESULTS: The cystatin C PETIA was analytically robust between 0.15 mg/L and 8.36 mg/L. PETIA cystatin C values were 27.5% higher than PENIA results. Furthermore, PENIA results were 12.9% lower in 2010 than in 2000. PETIA cystatin C values and existing equations performed reasonably well to estimate GFR with an overall -7.4% bias for all patients analyzed. Age and gender specific reference intervals were established for the PETIA cystatin C. CONCLUSIONS: Cystatin C can be precisely measured by PETIA traceable to the international reference material, ERM-DA471/IFCC, using a routine chemistry autoanalyzer. There are important biases between this assay and the widely employed Siemens PENIA. This study highlights the importance of assay standardization if cystatin C is to be widely used to estimate GFR.
BACKGROUND:Cystatin C is an alternative biomarker for assessing glomerular filtration rate (GFR), yet lack of standardization could hinder its widespread use. In this study we analytically and clinically validated a newer cystatin C particle-enhanced turbidimetric assay (PETIA) traceable to a certified reference material and compared it to the more commonly used particle-enhanced nephelometric assay (PENIA). METHODS: Samples from four patient cohorts at the Mayo Clinic were studied: 1) clinical convenience samples (n=50); 2) samples from patients undergoing iothalamate urinary clearance testing for clinical indications (n=101); 3) volunteers without kidney disease (n=292); 4) samples from 1999-2000 with previous cystatin C measurements. RESULTS: The cystatin C PETIA was analytically robust between 0.15 mg/L and 8.36 mg/L. PETIA cystatin C values were 27.5% higher than PENIA results. Furthermore, PENIA results were 12.9% lower in 2010 than in 2000. PETIA cystatin C values and existing equations performed reasonably well to estimate GFR with an overall -7.4% bias for all patients analyzed. Age and gender specific reference intervals were established for the PETIA cystatin C. CONCLUSIONS:Cystatin C can be precisely measured by PETIA traceable to the international reference material, ERM-DA471/IFCC, using a routine chemistry autoanalyzer. There are important biases between this assay and the widely employed Siemens PENIA. This study highlights the importance of assay standardization if cystatin C is to be widely used to estimate GFR.
Authors: Alina M Allen; W Ray Kim; Joseph J Larson; Colin Colby; Terry M Therneau; Andrew D Rule Journal: Transplantation Date: 2015-07 Impact factor: 4.939
Authors: Simon D S Fraser; Grant Aitken; Maarten W Taal; Jennifer S Mindell; Graham Moon; Julie Day; Donal O'Donoghue; Paul J Roderick Journal: PLoS One Date: 2015-02-20 Impact factor: 3.240
Authors: Jason N Barreto; Joel M Reid; Carrie A Thompson; Kristin C Mara; Andrew D Rule; Kianoush B Kashani; Nelson Leung; Thomas R Larson; Renee M McGovern; Thomas E Witzig; Erin F Barreto Journal: Clin Transl Sci Date: 2021-08-23 Impact factor: 4.689