Pitfalls in the diagnosis of hematuria.

Detection of hemoglobin (Hb) and red blood cells in urine (hematuria) is characterized by a large number of pitfalls. Clinicians and laboratory specialists must be aware of these pitfalls since they often lead to medical overconsumption or incorrect diagnosis. Pre-analytical issues (use of vacuum tubes or urine tubes containing preservatives) can affect test results. In routine clinical laboratories, hematuria can be assayed using either chemical (test strips) or particle-counting techniques. In cases of doubtful results, Munchausen syndrome or adulteration of the urine specimen should be excluded. Pigmenturia (caused by the presence of dyes, urinary metabolites such as porphyrins and homogentisic acid, and certain drugs in the urine) can be easily confused with hematuria. The peroxidase activity (test strip) can be positively affected by the presence of non-Hb peroxidases (e.g. myoglobin, semen peroxidases, bacterial, and vegetable peroxidases). Urinary pH, haptoglobin concentration, and urine osmolality may affect specific peroxidase activity. The implementation of expert systems may be helpful in detecting preanalytical and analytical errors in the assessment of hematuria. Correcting for dilution using osmolality, density, or conductivity may be useful for heavily concentrated or diluted urine samples.

Incidence, evolution and risk factors of hypophosphatemia in patients with solid tumors receiving ferric carboxymaltose: a retrospective cohort study.

OBJECTIVES: Ferric carboxymaltose (FCM) is increasingly used in the management of cancer-related anemia, yet it may cause hypophosphatemia. This retrospective study describes the incidence, evolution and risk factors of hypophosphatemia in a cohort of patients with solid tumors receiving FCM. METHODS: Serum phosphorus concentration was assessed longitudinally using a random intercepts model. The probability of developing hypophosphatemia, as graded by CTCAE version 4.0, was investigated using a multi-state model. Transition hazards were modeled non-parametrically and semi-parametrically by a Cox model. Causal marginal risk differences between baseline interventions on serum phosphorus and/or FCM dose were obtained via G-computation. RESULTS: In 174 ambulatory patients with solid tumors receiving FCM at two university hospitals between October 2020 and September 2021, the risk of developing moderate-to-severe hypophosphatemia was 36.0% (95% confidence interval (CI) 28.2-43.9%) and peaked within 16 days after first FCM administration. The average duration of moderate-to-severe hypophosphatemia was 12.4 days. After adjustment for confounders, lower baseline serum phosphorus (adjusted hazard ratio (aHR) 0.88 per 0.1 mmol/L increase, 95% CI 0.79-0.98) and higher FCM dose (first dose: aHR 1.12 per 1 mg/kg increase, 95% CI 1.01-1.25; second dose: aHR 1.06 per 1 mg/kg increase, 95% CI 1.00-1.13) significantly increased the hazard of moderate-to-severe hypophosphatemia. CONCLUSION: Approximately one out of three ambulatory patients with solid tumors may develop moderate-to-severe hypophosphatemia after FCM administration. Baseline serum phosphorus and FCM dose may be modifiable risk factors that should be considered for intervention in order to mitigate the risk of hypophosphatemia.

Shunt Nephritis: A Case of Mistaken Identity.

BACKGROUND: Membranoproliferative glomerulonephritis is a histological pattern of glomerular injury due to the deposition of immune complexes and complement factors. It is associated with bacterial and viral infections, auto-immune diseases such as systemic lupus erythematosus and Sjögren's syndrome, monoclonal gammopathy, and complement disorders (dense deposit disease and C3 glomerulopathy).  Case presentation: This is the report of a 25-year-old male with membranoproliferative glomerulonephritis who was initially treated for systemic lupus erythematosus, but who was later diagnosed with nephritis due to a chronic infection of a central nervous system shunt, last revised at the age of 3 years old. DISCUSSION: We highlight the challenges in making an early diagnosis of shunt nephritis, and succinctly discuss the clinical, biochemical, histopathological findings, and differential diagnosis of this type of infection-related glomerulonephritis.

Truth or dare: switching BRAF/MEK inhibitors after acute interstitial nephritis in a patient with metastatic melanoma - A case report and review of the literature.

INTRODUCTION: The introduction of BRAF/MEK inhibitors has significantly improved overall survival of patients with BRAF V600-mutant advanced or metastatic melanoma. Most patients treated with BRAF/MEK inhibitors will experience adverse events during the course of their treatment. Kidney impairment, however, was rarely reported in the pivotal trials. To date, there are only three cases of biopsy-proven acute interstitial nephritis associated with dabrafenib and trametinib reported in the literature. CASE REPORT: A 50-year-old man diagnosed with metastatic melanoma was hospitalized in August 2021, 5 months after treatment initiation with dabrafenib and trametinib. He presented with acute kidney injury, with serum creatinine of 3.34 mg/dL and eGFR of 20.3 mL/min/m². Kidney biopsy revealed acute interstitial nephritis. MANAGEMENT & OUTCOME: He was treated with methylprednisolone 16 mg qd, and both dabrafenib and trametinib were permanently discontinued, with recuperation of his kidney function. Another BRAF/MEK inhibitor combination, encorafenib and binimetinib, was introduced, with preserved kidney function and excellent disease control. DISCUSSION: We report the first case of biopsy-proven interstitial nephritis in a patient treated with dabrafenib and trametinib, with successful introduction of another BRAF/MEK inhibitor combination. Although rare, clinicians should be aware of the risk of renal adverse events associated with BRAF/MEK inhibitors. Renal biopsy is mandatory in the absence of a clear explanation or rapid recovery of renal failure. In case of proven interstitial nephritis, corticosteroids should be initiated. Switching to another BRAF/MEK inhibitor combination can be considered for patients with complete recovery of renal function and limited treatment options.

Immune Complex Glomerulonephritis in a Patient with Myelodysplastic Syndrome with Ring Sideroblasts Treated with Luspatercept.

Myelodysplastic syndromes (MDS) are a group of clonal myeloid disorders distinguished by dysplastic bone marrow and peripheral blood cells, ineffective hematopoiesis, and an increased risk of developing acute myeloid leukemia (AML). MDS with ring sideroblasts (MDS-RS) is a favorable outcome subtype with a lower frequency of AML transformation. The FDA recently approved luspatercept for the treatment of patients with very-low-, low-, and intermediate-risk MDS-RS who have failed to correct anemia with an erythropoiesis-stimulating agent (ESA) and require two units of red blood cells over an eight-week period. This drug's pharmacology is based on the critical role of the transforming growth factor-beta (TGF-ß) pathway in regulating erythropoiesis. In this case report, we describe for the first time an acute kidney injury caused by membranoproliferative glomerulonephritis (MPGN) in a patient with MDS-RS who was treated with luspatercept. We propose that a multi-hit hypothesis could explain the immunopathogenesis. A first unknown hit may stimulate IgA immune complex production, whereas luspatercept administration acts as a second hit, causing Smad1-5-8 phosphorylation. This intriguing case report on immune-complex-mediated proliferative glomerulonephritis following luspatercept treatment generates hypotheses and stimulates further research in this area.

Prediction of cardiac surgery associated - acute kidney injury (CSA-AKI) by healthcare professionals and urine cell cycle arrest AKI biomarkers [TIMP-2]*[IGFBP7]: A single center prospective study (the PREDICTAKI trial).

PURPOSE: Cardiac surgery associated acute kidney injury (CSA-AKI) is a contributor to adverse outcomes. Preventive measures reduce AKI incidence in high risk patients, identified by biomarkers [TIMP-2]*[IGFBP7] (Nephrocheck®). This study investigate clinical AKI risk assessment by healthcare professionals and the added value of the biomarker result. MATERIALS AND METHODS: Adult patients were prospectively included. Healthcare professionals predicted CSA-AKI, with and without biomarker result knowledge. Predicted outcomes were AKI based on creatinine, AKI stage 3 on urine output, anuria and use of kidney replacement therapy (KRT). RESULTS: One-hundred patients were included. Consultant and ICU residents were best in AKI prediction, respectively AUROC 0.769 (95% CI, 0.672-0.850) and 0.702 (95% CI, 0.599-0.791). AUROC of NephroCheck® was 0.541 (95% CI, 0.438-0.642). AKI 3 occurred in only 4 patients; there was no anuria or use of KRT. ICU nurses and ICU residents had an AUROC for prediction of AKI 3 of respectively 0.867 (95% CI, 0.780-0.929) and 0.809 (95% CI, 0.716-0.883); for NephroCheck® this was 0.838 (95% CI, 0.750-0.904). CONCLUSIONS: Healthcare professionals performed poor or fair in predicting CSA-AKI and knowledge of Nephrocheck® result did not improved prediction. No conclusions could be made for prediction of severe AKI, due to limited number of events.

Carbamoylated Nail Proteins as Assessed by Near-Infrared Analysis are Associated with Load of Uremic Toxins and Mortality in Hemodialysis Patients.

Carbamoylation is an important risk factor for accelerated atherogenesis and mortality in patients undergoing hemodialysis (HD). We intended to explore whether carbamoylation as assessed by near-infrared (NIR) analysis of nail proteins is associated with (a) serum concentrations of representative uremic toxins and (b) mortality in HD patients. A total of 53 healthy volunteers and 84 consecutive HD patients were enrolled in this cross-sectional cohort study. Standard laboratory methods were used to measure routine parameters, whereas levels of uremic toxins were determined using reversed-phase high-performance liquid chromatography (RP-HPLC). Spectra of distal fingernail clippings were obtained using an Avantes NIR spectrometer and processed using chemometric data analysis. The second derivative of the peak intensity at 1494 nm attributed to N-H amide bands from NH2 of carbamoyl (-CONH2) groups was higher in HD patients than in control subjects (p < 0.0001). Peak intensity levels were associated with age and plasma levels of representative uremic toxins. Cox-regression analysis revealed a significant association with all-cause mortality, even after adjustment for age. In conclusion, our data revealed that carbamoylation as assessed by NIR analysis of nail proteins is associated with serum concentrations of uremic toxins and also with mortality in HD patients. Further research to explore whether it is a surrogate marker or a hard indicator of mortality risk is warranted.

Detection and Characterization of a Biochemical Signature Associated with Diabetic Nephropathy Using Near-infrared Spectroscopy on Tissue Sections.

Histological evaluation of renal biopsies is currently the gold standard for acquiring important diagnostic and prognostic information in diabetic nephropathy (DN) patients. Nevertheless, there is an unmet clinical need for new biomarkers that allow earlier diagnosis and risk stratification. As biochemical changes in tissues must precede any symptomatic or morphological expression of a disease, we explored the potential of near-infrared (NIR) spectroscopy in the detection of a biochemical signature associated with DN. Kidney tissue sections were investigated using NIR spectroscopy, followed by principal component analysis and soft independent modelling of class analogy. A biochemical signature indicative of DN was detected, which enabled perfect discrimination between tissue sections with normal histological findings (n = 27) and sections obtained from DN patients (n = 26). Some spectral changes related to carbamoylation and glycation reactions appeared to be similar to the ones obtained in patients with DN. In addition, treatment with the deglycating enzyme fructosamine-3-kinase resulted in partial to pronounced restorations of the spectral pattern. Significant relationships were found between spectral features and laboratory parameters indicative of glycemic and uremic load, such as hemoglobin A1c, urea, creatinine, estimated glomerular filtration rate, and proteinuria. The presented method could be a useful tool to complement histopathological analysis in order to prevent or delay further disease progression, especially in the setting of post-transplant surveillance kidney biopsies.

Estimating the Level of Carbamoylated Plasma Non-High-Density Lipoproteins Using Infrared Spectroscopy.

BACKGROUND: The increased cardiovascular morbidity and mortality observed in chronic kidney disease (CKD) patients can be partly explained by the presence of carbamoylated lipoproteins. Lipid profiles can be determined with infrared spectroscopy. In this paper, the effects of carbamoylation on spectral changes of non-high-density lipoproteins (non-HDL) were studied. METHODS: In the present study, fasting serum samples were obtained from 84 CKD patients (CKD stage 3-5: n = 37 and CKD stage 5d (hemodialysis): n = 47) and from 45 healthy subjects. In vitro carbamoylation of serum lipoproteins from healthy subjects was performed using increasing concentrations of potassium cyanate. Lipoprotein-containing pellets were isolated by precipitation of non-HDL. The amount of carbamoylated serum non-HDL was estimated using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, followed by soft independent modelling by class analogy analysis. RESULTS: Carbamoylation resulted in a small increase of the amide I band (1714-1589 cm-1) of the infrared spectroscopy (IR) spectrum. A significant difference in the amide II/amide I area under the curves (AUC) ratio was observed between healthy subjects and CKD patients, as well as between the two CKD groups (non-dialysis versus hemodialysis patients). CONCLUSIONS: ATR-FTIR spectroscopy can be considered as a novel method to detect non-HDL carbamoylation.

Binding of bromocresol green and bromocresol purple to albumin in hemodialysis patients.

BACKGROUND: Colorimetric albumin assays based on binding to bromocresol purple (BCP) and bromocresol green (BCG) yield different results in chronic kidney disease. Altered dye binding of carbamylated albumin has been suggested as a cause. In the present study, a detailed analysis was carried out in which uremic toxins, acute phase proteins and Kt/V, a parameter describing hemodialysis efficiency, were compared with colorimetrically assayed (BCP and BCG) serum albumin. METHODS: Albumin was assayed using immunonephelometry on a BN II nephelometer and colorimetrically based on, respectively, BCP and BCG on a Modular P analyzer. Uremic toxins were assessed using high-performance liquid chromatography. Acute phase proteins (C-reactive protein and α1-acid glycoprotein) and plasma protein α2-macroglobulin were assayed nephelometrically. In parallel, Kt/V was calculated. RESULTS: Sixty-two serum specimens originating from hemodialysis patients were analyzed. Among the uremic toxins investigated, total para-cresyl sulfate (PCS) showed a significant positive correlation with the BCP/BCG ratio. The serum α1-acid glycoprotein concentration correlated negatively with the BCP/BCG ratio. The BCP/BCG ratio showed also a negative correlation with Kt/V. CONCLUSIONS: In renal insufficiency, the BCP/BCG ratio of serum albumin is affected by multiple factors: next to carbamylation, uremic toxins (total PCS) and α1-acid glycoprotein also play a role.

Mechanisms and consequences of carbamoylation.

Protein carbamoylation is a non-enzymatic post-translational modification that binds isocyanic acid, which can be derived from the dissociation of urea or from the myeloperoxidase-mediated catabolism of thiocyanate, to the free amino groups of a multitude of proteins. Although the term 'carbamoylation' is usually replaced by the term "carbamylation" in the literature, carbamylation refers to a different chemical reaction (the reversible interaction of CO2 with α and ε-amino groups of proteins). Depending on the altered molecule (for example, collagen, erythropoietin, haemoglobin, low-density lipoprotein or high-density lipoprotein), carbamoylation can have different pathophysiological effects. Carbamoylated proteins have been linked to atherosclerosis, lipid metabolism, immune system dysfunction (such as inhibition of the classical complement pathway, inhibition of complement-dependent rituximab cytotoxicity, reduced oxidative neutrophil burst, and the formation of anti-carbamoylated protein antibodies) and renal fibrosis. In this Review, we discuss the carbamoylation process and evaluate the available biomarkers of carbamoylation (for example, homocitrulline, the percentage of carbamoylated albumin, carbamoylated haemoglobin, and carbamoylated low-density lipoprotein). We also discuss the relationship between carbamoylation and the occurrence of cardiovascular events and mortality in patients with chronic kidney disease and assess the effects of strategies to lower the carbamoylation load.

Sensitive albuminuria analysis using dye-binding based test strips.

BACKGROUND: Populations at increased risk for chronic kidney disease should be screened for albuminuria. Possibilities of advanced urine strip readers based on complementary metal oxide semiconductor (CMOS) sensor technology were investigated for obtaining quantitative albuminuria results. METHODS: Reflectance data of test strips (Sysmex UFC 3500 reader+CMOS) were compared with albuminuria (BNII) and with proteinuria (Cobas 8000). Urinary creatinine was assayed using a Jaffe-based creatinine assay (Cobas 8000). RESULTS: Calibration curve was made between 11.5 and 121.5mg/L with detection limit of 5.5mg/L. Within-run CV values of reflectance data were 0.21% (UC-Control L; 10mg/L) and 0.37% (UC-Control H; >150mg/L) for albumin, and 0.71%/3.97% for creatinine. Between-run CV values were 0.24%/0.42% for albumin and 0.93%/5.13% for creatinine. A strong correlation (r=0.92) was obtained between albuminuria (BNII) and protein strip reflectance data. Creatinine reflectance data correlated well with Jaffe-based urinary creatinine data (r=0.90). Albumin:creatinine ratio obtained by test strip and by wet chemistry showed a good correlation (r=0.59). Carbamylated, glycated and partially hydrolyzed isoforms of albumin could be detected by test strip. CONCLUSIONS: Dye-binding based albumin test strip assay in combination with a CMOS based reader would potentially allow quantitative analysis of albuminuria and determination of albumin:creatinine ratio.

Quantification of carbamylated albumin in serum based on capillary electrophoresis.

Protein carbamylation, a nonenzymatic posttranslational modification promoted during uremia, is linked to a poor prognosis. In the present study, carbamylation of serum albumin was assayed using the symmetry factor on a capillary electrophoresis instrument (Helena V8). The symmetry factor has been defined as the distance from the center line of the peak to the back slope, divided by the distance from the center line of the peak to the front slope, with all measurements made at 10% of the maximum peak height. Serum albumin, creatinine, and urea concentrations were assayed using routine methods, whereas uremic toxins were determined using HPLC. In vitro carbamylation induced a marked albumin peak asymmetry. Reference values for the albumin symmetry factor were 0.69-0.92. In kidney patients, albumin peak asymmetry corresponded to the chronic kidney disease stage (p < 0.0001). The symmetry factor correlated well with serum urea (r = -0.5595, p < 0.0001) and creatinine (r = -0.5986, p < 0.0001) concentrations. Several protein-bound uremic toxins showed a significant negative correlation with the symmetry factor. Morphology of the albumin fraction was not affected by presence of glycated albumin and protein-bound antibiotics. In conclusion, the presented method provides a simple, practical way for monitoring protein carbamylation.