Should kidney tubular markers be adjusted for urine creatinine? The example of urinary cystatin C
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Marc Conti
Abstract
Background: Evaluation of specific urinary markers with respect to urine creatinine (uCreat) is common. However, as uCreat is a function of both glomerular filtration and tubular secretion, using uCreat for specific tubular markers, suggests that glomerular function is normal, and there is no tubular secretion. Thus, adjusting values of any tubular marker to uCreat, especially in patients with acute or even moderate chronic renal failure, can be misleading.
Methods: Using urine cystatin-C (uCST3) as a model tubular marker for following 120 kidney graft recipients daily, we evaluated the utility of either uCST3 alone or the uCST3/uCreat ratio to detect tubular damage. All positive kidney biopsies were always associated with a uCST3>0.18 mg/L.
Results: Using the uCST3/uCreat ratio, discrepancies regarding biopsy status were observed in nine patients (4 false positive, 5 false negative results). In two patients, variability of uCreat appeared to be the most important factor causing inconsistent uCST3/uCreat ratios. With a negative predictive value (NPV) of 85.7%, uCST3/uCreat can lead to errors in clinical interpretation. These errors can be avoided when estimates of tubular damage are based on uCST3 concentrations alone (NPV=100%).
Conclusions: We recommend using the uCST3 value to evaluate the extent of renal tubular damage. Indeed, our conflicting results on uCST3/uCreat can be extended to every marker of tubular function. Evaluating a urine marker specific for renal tubular damage to a second urine marker that is itself strongly dependent upon glomerular or other renal or non-renal conditions, impairs its clinical relevance and may lead to incorrect interpretations. Correction with uCreat can be performed only in pure glomerulopathy, when specific markers of glomerular function are measured (i.e., urinary albumin). In all other cases of renal diseases, such correction is inappropriate and should be avoided.
Clin Chem Lab Med 2009;47:1553–6.
©2009 by Walter de Gruyter Berlin New York
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- Validation and Outcome Studies
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- Acknowledgement
- Acknowledgement
- Contents
- Contents, Volume 47, 2009
- Author Index
- Author Index
- Subject Index
- Subject Index
Artikel in diesem Heft
- Review
- Multiple gene interaction and modulation of hemostatic balance
- Minireview
- Appropriate utilization of clinical laboratory tests
- Genetics and Molecular Diagnostics
- Quantitation of RNA decay in dried blood spots during 20 years of storage
- ROS1 Asp2213Asn polymorphism is not associated with coronary artery disease in a Greek case-control study
- Association of glutathione-S-transferase polymorphisms with atopic dermatitis risk in preschool age children
- Haplotype-based association of regulator of G-protein signaling 5 gene polymorphisms with essential hypertension and metabolic parameters in Chinese
- A new automated human leukocyte antigen genotyping strategy to identify DR-DQ risk alleles for celiac disease and type 1 diabetes mellitus
- General Clinical Chemistry and Laboratory Medicine
- Serum thyrotropin and free thyroxine reference ranges as defined in a disease-free sample of French middle-aged adults
- Screening for M-proteinemia: serum protein electrophoresis and free light chains compared
- Temporal profile and clinical significance of serum neuron-specific enolase and S100 in ischemic and hemorrhagic stroke
- Salivary neuron specific enolase: an indicator for neuronal damage in patients with ischemic stroke and stroke-prone patients
- Antibodies to mutated citrullinated vimentin and antibodies to cyclic citrullinated peptides in juvenile idiopathic arthritis
- Age-associated developmental changes in the activated partial thromboplastin time (APTT) and causes of prolonged APTT values in healthy Chinese children
- Nucleated red blood cells and soluble transferrin receptor in thalassemia syndromes: relationship with global and ineffective erythropoiesis
- Serum chitotriosidase enzyme activity in patients with Crimean-Congo hemorrhagic fever
- Preanalytical mistakes in samples from primary care patients
- Should kidney tubular markers be adjusted for urine creatinine? The example of urinary cystatin C
- Validation and Outcome Studies
- Development and analytical performance evaluation of an automated chemiluminescent immunoassay for pro-gastrin releasing peptide (ProGRP)
- Development and validation of a liquid chromatography-tandem mass spectrometry assay for serum 25-hydroxyvitamin D2/D3 using a turbulent flow online extraction technology
- Letters to the Editor
- Lack of association between eNOS Glu298Asp gene polymorphism and carotid atherosclerosis in a Serbian population
- Falsely elevated troponin I attributed to collection tubes using the Vitros ECiQ system
- Processing effects and storage conditions on A Disintegrin And Metalloprotease (ADAM12s), a maternal serum marker for adverse pregnancy outcome
- Serum γ-glutamyltransferase: linking together environmental pollution, redox equilibria and progression of atherosclerosis?
- The impact factor for evaluating scientists: the good, the bad and the ugly
- Acknowledgement
- Acknowledgement
- Contents
- Contents, Volume 47, 2009
- Author Index
- Author Index
- Subject Index
- Subject Index
