PRECISION, BIAS, AND LINEAR RANGE OF THE CYSTATIN C ASSAY ON THE ROCHE COBAS C502 SYSTEM
Main Article Content
Abstract
Background: Accurate estimation of the glomerular filtration rate (eGFR) is crucial for managing chronic kidney disease. Cystatin C is a superior biomarker that addresses the “creatinine blind spot”. According to ISO 15189:2022, verifying assay performance on specific analytical systems is mandatory.
Objective: To evaluate the precision, bias, and linearity of the Cystatin C assay on the Roche Cobas c502 system.
Methods: A cross-sectional descriptive study was conducted from November 2024 to July 2025. Precision and bias were assessed using two levels of internal quality control (QC). The linear range was determined across five dilution levels (0.4–6.8 mg/L). Data were analyzed using ANOVA and linear regression, then compared against the total allowable error (TEa = 7.61%).
Results: Precision: Short-term precision (%CV) was 1.04% and 0.81%; long-term precision was 0.82% and 0.72% for the two QC levels, both meeting manufacturer specifications. Accuracy: Experimental bias (0.24% and 0.29%) and Total Error (1.59% and 1.48%) were well within acceptable limits. Linearity: A strong correlation was observed with the equation y = 1.0163x + 0.0315 and R2 = 0.9992 within the range of 0.4–6.8 mg/L.
Conclusion: The Cystatin C assay on the Roche Cobas c502 system fulfills all quality requirements for precision, accuracy, and linearity. This procedure ensures high reliability for the clinical diagnosis and monitoring of renal diseases.
Keywords
Cystatin C, method verification, precision, bias, linearity
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References
2. Hương Bùi Thị Thu, Giang Nguyễn Thu. Giá trị của Cystatin C trong chẩn đoán sớm tổn thương thận ở bệnh nhân đái tháo đường typ 2 tại Bệnh viện Trung ương Thái Nguyên, Tạp chí Y học Việt Nam, 2021, 498(2).
3. SW Benoit, EA Ciccia, P Devarajan. Cystatin C as a biomarker of chronic kidney disease: latest developments, Expert Rev Mol Diagn, 2020, 1019-1026.
4. Clinical and Laboratory Standards Institute, User Verification of Precision and Estimation of Bias; Approved Guideline-Third Edition (EP15-A3), Clinical and Laboratory Standards Institute, 2014, 1-48.
5. International Organization for Standardization, Medical laboratories - Requirements for quality and competence (ISO 15189:2022), International Organization for Standardization, 2022, 1-104.
6. Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group, KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease, Kidney Int, 2024, S117-S314.
7. EJ Lamb, J Barratt, EA Brettell và cộng sự. Accuracy of glomerular filtration rate estimation using creatinine and cystatin C for identifying and monitoring moderate chronic kidney disease: the eGFR-C study, Health Technol Assess, 2024, 1-169.
8. WA Mula-Abed, K Al Rasadi, D Al-Riyami. Estimated Glomerular Filtration Rate (eGFR): A Serum Creatinine-Based Test for the Detection of Chronic Kidney Disease and its Impact on Clinical Practice, Oman Med J, 2012, 108-113.