Urine Cystatin C Determination in the Establishment of Reference Interval in the Diagnosis and Treatment of Renal Injury

BACKGROUND We evaluated the analytical performance of 4 cystatin C assays (Siemens N Latex on BNII, Roche Tina-quant on Cobas c501, Genzyme on Cobas c501, and Tosoh ST AIA-PACK on Tosoh AIA-600II) according to guidelines published by the Clinical and Laboratory Standards Institute. METHODS We evaluated total imprecision, limit of detection, and limit of quantification for each assay using patient serum pools and linearity/recovery using serial dilutions of a patient serum pool with cystatin C–free serum. We compared patients (n = 102) using the Siemens assay as a comparison method. RESULTS All assays had limits of detection and quantification <0.08 and <0.39 mg/L, respectively. Total CVs were generally higher than the manufacturers' claims for all assays. The Roche assay overrecovered cystatin C, particularly at low concentrations (mean recovery 119%, 142% at 0.587 mg/L). Deming regression equations were y = 1.184x + 0.089, Sy|x = 0.246 for Genzyme; y = 0.937x + 0.231, Sy|x = 0.231 for Roche; and y = 1.010x + 0.216, Sy|x = 0.115 for Tosoh. The Genzyme assay appeared to report higher results than the Siemens assay, which is consistent with a higher reference interval specified by the manufacturer. CONCLUSIONS Although all assays were acceptable for clinical use, their diagnostic performances were not optimal. Limitations include imprecision greater than claimed, overrecovery for the Roche assay on low concentration samples, and differences in results for patient samples. The latter situation requires assay-specific cystatin C–based glomerular filtration rate prediction equations at least until calibration is standardized using the international cystatin C calibrator now being developed.

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SERUM NEUTROPHIL GELATINASE-ASSOCIATED LIPOCALIN (NGAL) AND URINARY NGAL EXCRETION AS A BIOMARKER OF RENAL INJURY IN CHILDREN WITH BETA THALASSEMIA MAJOR

10.36106/ijar/9602275 ◽

2021 ◽

pp. 1-3

Author(s):

Ruchi Bhatt ◽

Alok Hemal ◽

Meetu Singh ◽

Zeeshan Ahmed

Keyword(s):

Cystatin C ◽

Renal Injury ◽

Linear Regression Analysis ◽

Thalassemia Major ◽

Beta Thalassemia ◽

P Value ◽

Urinary Ngal ◽

Urine Ngal ◽

Beta Thalassemia Major ◽

Serum And Urine

Background Frequent blood transfusions among patients with beta thalassemia major leads to iron overload state and leads to damage of various organs including kidney. Very few studies have explored on Serum and urinary NGAL as a biomarkers of renal injury in thalassemia major children. Therefore, this study is planned to investigate the renal injury in beta thalassemic children by measuring serum and urinary NGAL levels and correlating it with cystatin c and creatinine clearance. Methods: The study was a cross-sectional conducted among 25 patients with β thalassemia major, aged 1-18 years, having undergone regular blood transfusion and chelation therapy. Levels of plasma and urinary NGAL were measured and compared to the standard values of the normal range. Linear regression analysis was done. Results: Mean(SD) serum NGAL value in 1- 5 years of age was 1.6(0.26) , in 5-10 years was 2.15(0.23), in 10- 15 years was 2.6 (0.11) and > 15 years it was 18.11(33.76). ( p value <0.005).Mean (SD) urine NGAL value in 1- 5 years of age was 0.66 (0.11) , in 5-10 years was 1.13(0.13), in 10- 15 years was 1.38 (0.18) and > 15 years it was 1.94(0.25). ( p value <0.005).The mean values of plasma N-GAL, and Urinary N-GAL were significantly higher in our patients as compared to that of standard population values(p<0.05). Conclusions: Serum and urine NGAL values are found to be much higher in those with longer duration of transfusion and chelation. Positive correlation was found between urine NGAL levels and cystatin C. Serum and urine NGAL values are fair markers of renal injury in thalassemia major patients on multiple transfusions.

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