Biochimica Clinica: VOL.45 N. Special Supplement 1

The diagnosis and follow-up of acute kidney injury (AKI) has traditionally been based on clinical parameters such as urine output, and/or biomarkers such as serum creatinine (sCr), which are not very sensitive. The identification and validation of novel biomarkers, capable of recognizing an increased risk of AKI, a renal damage before or without a functional renal loss (i.e. subclinical AKI) and a renal dysfunction prior to the increase in sCr levels, has reviewed the diagnosis and classification of AKI. Thanks to these biomarkers, a new conceptual model of AKI, that includes the full spectrum of events and conditions, has been developed. At each stage of this model, biomarkers may contribute to explain the mechanisms and to predict the clinical evolution of kidney damage. Several biomarkers have been identified. They differ in anatomical origin, physiological function, kinetics and detecting time after kidney injury.
The present review describes the main biomarkers’ characteristics and their role in the clinical practice.

Metastatic clear cell renal cell carcinoma is a high vascularized and aggressive tumor characterized by a high intra-tumoral and inter-tumoral heterogeneity. For this reason, despite the wide range of therapy available, these patients often show resistance to chemotherapy. In this scenario, it could be of great benefit the discovery of biomarkers to identify the most suitable treatment for first and second line therapy and the early determination of outcome. Once identified, circulating biomarkers could be introduced in clinical practice and integrated with patient’s clinical features for building a decision algorithm usable by clinicians. The liquid biopsy, defined as the determination in fluids like blood of tumor-released product such as DNA, RNA and protein, exhibits several advantages over tissue biomarkers including a real time correlation with tumor features, lower cost and lower risk for the patient. Our understanding of the liquid biopsy has raised rapidly in the last few years accordingly with the development of new molecular biology techniques. Efforts are under way for the identification of robust and reproducible liquid biopsy assays that could improve soon overall survival (OS) and quality of life of metastatic renal cell carcinoma.

Renal amyloidoses are a group of rare misfolding protein diseases caused by the deposition of a precursor protein in the kidney as insoluble amyloid fibrils, causing renal damage and dysfunction that can progress to end-stage renal failure requiring dialysis. This heterogeneous group includes commoner diseases as light chain (AL) and reactive (AA) amyloidosis as well as rarer entities as hereditary renal amyloidosis. Differential diagnosis is mandatory to avoid therapeutic errors and requires amyloid typing on tissue biopsy and, in selected cases, DNA analysis. In AL and AA amyloidosis, biomarkers are well-established tools that help clinicians in diagnosis, prognosis assessment and evaluation of treatment efficacy, highlighting the important role of the clinical laboratory in the management of these rare diseases. In AL amyloidosis, the identification of the monoclonal protein requires the combination of electrophoresis, immunofixation of both serum and urine, and serum free light chain (FLC) assessment. Severity of renal involvement and risk of progression to dialysis are predicted at diagnosis by 24h-proteinuria and estimated glomerular filtration rate (eGFR). Treatment efficacy is assessed with monoclonal protein studies, including serum FLC measurement; hematologic response can result in improvement of renal damage, evaluated by improvements in 24h-proteinuria and eGFR from baseline. In AA amyloidosis, a periodical evaluation of serum amyloid A (SAA) serum concentration reflects the activity of the underlying inflammatory disease and evaluates the efficacy of treatment. The severity of renal involvement can be assessed at diagnosis with 24h-proteinuria and eGFR. Only few data on prognostic markers are available on other types of renal amyloidosis.

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is a major genetic disorder affecting up to 12.5 million individuals worldwide and it is the fourth most common global cause for renal replacement therapy.
ADPKD is a chronic, progressive condition characterized by the development and growth of cysts in the kidneys and other organs and by additional systemic manifestations. Two causative genes have been identified: PKD1 and PKD2. ADPKD phenotype is highly variable intra and inter-family. Typically, ADPKD is an adult onset disease. However, occasionally, ADPKD manifests as very early onset disease. Heritability of ADPKD is a complex matter due to different causes such as hypomorfic alleles, digenic heritance, mosaicism and modifier genes. The phenotypic variability of ADPKD can be explained at three genetic levels: genic, allelic and gene modifier effects. Recent advances in molecular screening for PKD gene mutations have generated considerable improvement regarding the knowledge of genetic basis of ADPKD. The purpose of this paper is to provide a comprehensive review of the genetics of ADPKD, focusing on new insights in genotype-phenotype correlation and explaining the tremendous hereditability complexity. Evaluation of these new genetic information requires a multidisciplinary approach involving nephrologists and genetists, taking care of patients (and their families) considering clinical and genetic aspects.

Chronic kidney disease is a major type of kidney disease where a gradual loss of kidney function over a period of months to years can be observed. Its early detection is critical in improving the clinical outcome. It may be associated to diabetes, the illness being cause of the nephropathy, and then the condition is known as diabetic kidney disease (DKD). However, it may be associated to diabetes, but the pathogenesis arising could be attributable to other reasons, and then the condition is known as non diabetic kidney disease (NDKD). In this review we will focus on these two conditions, and we will briefly outline the state of the art of some traditional biomarkers (the quantitative determination of albumin in urine, eGFR), the role and the interpretation of some established biomarkers for the evaluation of glycemic control (glycated hemoglobin and glycated albumin) and the potential use of other new biomarkers useful to predict the development of the nephropathy.

Objective: Kidney markers are some of the most frequently used laboratory tests in patient care, and correct clinical decision making depends upon knowledge and correct application of biological variation (BV) data. The aim of this study was to review available BV data and to provide updated BV estimates for the following kidney markers in serum and plasma; albumin, creatinine, cystatin C, chloride, potassium, sodium and urea.  
Content: Relevant studies were identified from a historical BV database as well as by systematic literature searches. Retrieved publications were appraised by the Biological Variation Data Critical Appraisal Checklist (BIVAC). Metaanalyses of BIVAC compliant studies with similar design were performed to deliver global estimates of within-subject (CVI) and between-subject (CVG) BV estimates. Out of the 61 identified papers, three received a BIVAC grade A, four grade B, 48 grade C, five grade D grade and one was not appraised as it did not report numerical BV estimates. Most studies were identified for creatinine (n=48). BV estimates derived from the meta-analysis were in general lower than previously reported estimates for all analytes except urea. For some measurands, BV estimates may be influenced by age or states of health, but further data are required.  
Summary: This review provides updated global BV estimates for kidney related measurands. For all measurands except for urea, these estimates were lower than previously reported.  
Outlook: For the measurands analyzed in this review, there are sufficient well-designed studies available to publish a trustworthy estimate of BV. However, for a number of newly appearing kidney markers no suitable data is available and additional studies are required.  

Introduction: Human Epididymis Secretory Protein 4 (HE4) serum concentrations have been widely investigated in patients with ovarian cancer. However, high levels of HE4 can be also found in other tumors and in renal fibrosis. The aim of this study was to assess serum HE4 levels in a cohort of patients with IgA Nephropathy (IgAN) and the correlation of this potential biomarker with the degree of fibrosis.
Methods: the study included 63 Italian patients with histological diagnosis of IgAN (41 males and 22 females) where HE4 was measured at the time of renal biopsy using a chemiluminescent assay (Abbott Laboratories, Wiesbaden, Germany). The biopsy was scored according to the current Oxford classification using MEST score. The relationship between HE4 and each of the MEST parameters was analyzed by a non-parametric method. A ROC curve analysis was performed to assess the diagnostic accuracy of HE4 in identifying the presence of fibrosis.
Results: serum HE4 concentrations were significantly increased across the progressive degrees of fibrosis related T parameter (p <0.0001) [(median; interquartile range (IQR): T0 = 57.5 pmo/L (43.7-100.7); T1 = 106.0 pmo/L (78.0-149.0); T2 = 210.5 pmo/L (148.2-320.2)]. The ROC curve analysis, after adjusting for age and sex, showed that HE4 is diagnostic for the presence of fibrosis with an Area Under the Curve of 0.79 (95%CI: 0.68-0.91).
Conclusions: the relationship between serum level of HE4 and the degree of interstitial fibrosis suggests the potential role of HE4 as useful biomarker in IgAN.

Introduction: the diagnosis and classification of Chronic Kidney Disease (CKD) are based on laboratory tests. The aim of this paper is to verify their harmonization at national level, through the examination of participants’ results to EQA programs of the Centre of Biomedical Research.
Methods: we considered results of creatinine and eGFR of the last 8 EQA cycles (2013-2020) for a total of 80 lyophilized control samples and results of albumin and albumin/creatinine ratio (ACR) in urine of the last 3 EQA cycles (2018-2020) for a total of 24 lyophilized control materials.
Results: for creatinine measurement, enzymatic assays show the best accuracy, but only 40% of participants use them. For eGFR the 64% of participants use the equation derived by the CKD-Epidemiology Collaboration (CKD-EPI) study and this formula applied to enzymatic creatinine shows the best performances. For urine albumin, analytical variability (median CV%) is lower for all diagnostic systems at pathological concentrations than at concentrations below the cut-off. Important bias still exists between different methods and overall 12% of the albumin results provided by the participating laboratories did not reach the minimum quality level for the clinical use of the measure and for value <30.0 mg/L the number of unacceptable performances increases to 24%. Similar results were found for ACR: overall 14% of the results were unacceptable and for value <3.4 mg/mmol the number of unacceptable performances increases to 21%.
Conclusion: even if some improvements can be observed during the recent years, efforts for a better alignment to international recommendations are needed. A Reference system of higher order is needed to enable standardization of urine albumin measurement results. The participation in specific External Quality Programs is a valuable tool to assess the harmonization of laboratory tests for CKD diagnosis in our country.

In this paper I briefly discuss what the nephrologist means by “renal function” from a clinical point of view, and what can be inferred from the determination of the Glomerular Filtration Rate (GFR). Furthermore, I illustrate the use of serum biomarkers: serum creatinine, and GFR (measured and estimated GFR with different formulas), together with their limitations in different clinical conditions (acute kidney injury versus chronic kidney disease), different ages, different patients (obese, HIV patientsts, different ethnic groups). Forthcoming new methods for the point-of-care, rapid GFR determination are described with their possible implications in the acute kidney injury setting.

Secondary hyperparathyroidism (HPT) is a common issue in dialysis patients; it contributes significantly to their morbidity and mortality. Here we describe the case of a hemodialysis patient with severe secondary HPT, treated with Etelcalcetide, the new intravenous calcimimetic agent, employed after a nephrectomy due to a renal neoplasm to reduce successfully the serum levels of parathyroid hormone (PTH) and bone specific alkaline phosphatase (BAP). No significant change in serum calcium was recorded during treatment, while the already high serum phosphorus concentrations further increased after surgery. By maintaining the calcium mimetic therapy, even if at lower doses, the concentrations of PTH and BAP remained constant over the time.