Prevalence and factors associated with masked hypertension in chronic kidney disease.

OBJECTIVES: Optimal blood pressure (BP) control is key to prevent cardiovascular complications in patients with chronic kidney disease (CKD). We described the prevalence and factors associated with masked hypertension in CKD. METHODS: We analyzed 1113 ambulatory 24-h BP monitoring (ABPM) records of 632 patients referred for kidney function evaluation. Masked hypertension was defined as office BP less than 140/90 mmHg but daytime BP at least 135/85 mmHg or nighttime BP at least 120/70 mmHg. Factors associated with masked hypertension were assessed with mixed logistic regression models. RESULTS: At inclusion, 424 patients (67%) had controlled office BP, of whom 56% had masked hypertension. In multivariable analysis conducted in all visits with controlled office BP ( n  = 782), masked hypertension was positively associated with male sex [adjusted OR (95% confidence interval) 1.91 (1.16-3.27)], sub-Saharan African origin [2.51 (1.32-4.63)], BMI [1.11 (1.01-1.17) per 1 kg/m 2 ], and albuminuria [1.29 [1.12 - 1.47] per 1 log unit), and was negatively associated with plasma potassium (0.42 [0.29 - 0.71] per 1 mmol/L) and 24-h urinary potassium excretion (0.91 [0.82 - 0.99] per 10 mmol/24 h) as well as the use of renin-angiotensin-aldosterone (RAAS) blockers (0.56 [0.31 - 0.97]) and diuretics (0.41 [0.27 - 0.72]). CONCLUSION: Our findings support the routine use of ABPM in CKD, as more than half of the patients with controlled office BP had masked hypertension. Weight control, higher potassium intake (with caution in advanced CKD), correction of hypokalemia, and larger use of diuretics and RAAS blockers could be potential levers for better out-of-office BP control.

[Integrating pathology and biology into medical education: current state and future directions]. / Anatomopathologie et biologie médicale : quelle place dans la formation des étudiants en médecine ?

Pathology and biology are essential in the patient care. However, they suffer from a lack of attractiveness to medicine students. In order to gain insight and improve the visibility and attractiveness of these specialties, we designed a survey and submitted forms to medical students, laboratory medical staff, and clinical staff from the different hospitals and institutes attached to "Université Paris Cité". The responses (363 students (response rate: 9.1%), 109 medical -laboratory staff (25%), 61 clinical staff (10%)) confirmed the poor visibility of these specialties among students as well as the will of the -medical laboratory staff to be more involved in the student's training. The -development of partnerships between laboratories and clinical -departments, which would allow medical students to spend short periods of time in related laboratories during their clinical internship, is a prospect for improving the teaching of these disciplines. The main expected benefits are to "discover a new specialty" and "to better understand the prescription of laboratory tests", which are crucial aspects for understanding the role of laboratory disciplines and their interaction with clinicians to improve patient care.

Rescaling creatinine makes GFR estimation equations generally applicable across populations - validation results for the Lund-Malmö equation in a French cohort of sub-Saharan ancestry.

OBJECTIVES: To make glomerular filtration rate (GFR) estimating equations applicable across populations with different creatinine generation by using rescaled serum creatinine (sCr/Q) where sCr represents the individual creatinine level and Q the average creatinine value in healthy persons of the same population. METHODS: GFR measurements (mGFR, plasma clearance of 51Cr-EDTA) were conducted in 964 adult Black Europeans. We established the re-expressed Lund-Malmö revised equation (r-LMR) by replacing serum creatinine (sCr) with rescaled creatinine sCr/Q. We evaluated the r-LMR equation based on Q-values of White Europeans (r-LMRQ-white; Q-values females: 62 µmol/L, males: 80 µmol/L) and Black Europeans (r-LMRQ-Black; Q-values females: 65 µmol/L, males: 90 µmol/L), and the European Kidney Function Consortium equation (EKFCQ-White and EKFCQ-Black) regarding bias, precision (interquartile range, IQR) and accuracy (percentage of estimates within ±10 % [P10] and ±30 % [P30] of mGFR). RESULTS: Median bias of r-LMRQ-White/r-LMRQ-Black/EKFCQ-White/EKFCQ-Black were -9.1/-4.5/-6.3/-0.9 mL/min/1.73 m2, IQR 14.7/14.5/14.5/15.6 mL/min/1.73 m2, P10 25.1 %/34.8 %/30.3 %/37.2 % and P30 74.2 %/84.1 %/80.6 %/83.6 %. The improvement of bias and accuracy when using proper Q-values was most pronounced in men. Similar improvements were obtained above and below mGFR 60 mL/min/1.73 m2 and at various age and BMI intervals, except for BMI<20 kg/m2 where bias increased, and accuracy decreased. CONCLUSIONS: GFR estimating equations may be re-expressed to include rescaled creatinine (sCr/Q) and used across populations with different creatinine generation if population-specific average creatinine concentrations (Q-values) for healthy persons are established.

Fibroblast growth factor 23 but not copeptin is independently associated with kidney failure and mortality in patients with chronic kidney disease.

Background: Copeptin and intact fibroblast growth factor 23 (iFGF23) increase early during chronic kidney disease (CKD) and may be predictive of unfavourable outcomes. The aim of this study was to evaluate their respective associations with renal and vital outcomes in CKD patients. Methods: We included CKD patients from the NephroTest cohort with concomitant measurements of plasma copeptin and iFGF23 concentrations and isotopic glomerular filtration rate measurement (mGFR). The primary endpoint was a composite outcome including kidney failure (KF) (dialysis initiation, pre-emptive transplantation or a 57% decrease of mGFR, corresponding to doubling of serum creatinine) or death before KF. Hazard ratios (HRs) of the primary endpoint associated with log-transformed copeptin and iFGF23 concentrations were estimated by Cox models. The slope of mGFR over time was analysed using a linear mixed model. Results: A total of 329 CKD patients (243 men, mean age 60.3 ± 14.6 years) were included. Among them, 301 with an mGFR >15 ml/min/1.73 m2 were included in survival and mGFR slope analyses. During a median follow-up of 4.61 years (quartile 1-quartile 3: 3.72-6.07), 61 KFs and 32 deaths occurred. Baseline iFGF23 concentrations were associated with the composite outcome after multiple adjustments {HR 2.72 [95% confidence interval (CI) 1.85-3.99]}, whereas copeptin concentrations were not [HR 1.01 (95% CI 0.74-1.39)]. Neither copeptin nor iFGF23 were associated with mGFR slope over time. Conclusion: Our study shows for the first time in population of CKD patients an independent association between iFGF23 and unfavourable renal and vital outcomes and shows no such association regarding copeptin, encouraging the integration of iFGF23 measurement into the follow-up of CKD.

Diagnostic standard: assessing glomerular filtration rate.

Creatinine-based estimated GFR (eGFR) is imprecise at individual level, due to non-GFR-related serum creatinine determinants, including atypical muscle mass. Cystatin C has the advantage of being independent on muscle mass, a feature that led to the development of race- and sex-free equations. Yet, cystatin C-based equations do not perform better than creatinine-based equations to estimate GFR, unless both variables are included together. The new race-free Chronic Kidney Disease Epidemiology (CKD-EPI) equation, had slight opposite biases between Black and Non-Black subjects in USA, but performs poorer than that the previous version in European populations. The European Kidney Function Consortium (EKFC) equation developed in 2021 can be used both in children and adults, is more accurate in young and old adults, and is applicable to non-white European populations, by rescaling the Q factor, i.e. population median creatinine, in a potentially universal way. A sex- and race-free cystatin C-based EKFC, with the same mathematical design, has also be defined. New developments in the field of GFR estimation would be standardization of cystatin C assays, development of creatinine-based eGFR equations that would incorporate muscle mass data, implementation of new endogenous biomarkers, and the use of artificial intelligence. Standardization of different GFR measurement methods would also be a future challenge, as well as new technologies for measuring GFR. Future research is also needed on discrepancies between cystatin C and creatinine, which is associated with high risk of adverse events: standardize the definition of discrepancy, and understand its determinants.

Development and validation of a new equation based on plasma creatinine and muscle mass assessed by CT scan to estimate glomerular filtration rate: a cross-sectional study.

Background: Inter-individual variations of non-glomerular filtration rate (GFR) determinants of serum creatinine, such as muscle mass, account for the imperfect performance of estimated GFR (eGFR) equations. We aimed to develop an equation based on creatinine and total lumbar muscle cross-sectional area measured by unenhanced computed tomography scan at the third lumbar vertebra. Methods: The muscle mass-based eGFR (MMB-eGFR) equation was developed in 118 kidney donor candidates (iohexol clearance) using linear regression. Validation cohorts included 114 healthy subjects from another center (51Cr-EDTA clearance, validation population 1), 55 patients with chronic diseases (iohexol, validation population 2), and 60 patients with highly discordant creatinine and cystatin C-based eGFR, thus presumed to have atypical non-GFR determinants of creatinine (51Cr-EDTA, validation population 3). Mean bias was the mean difference between eGFR and measured GFR, precision the standard deviation (SD) of the bias, and accuracy the percentage of eGFR values falling within 20% and 30% of measured GFR. Results: In validation population 1, performance of MMB-eGFR was not different from those of CKD-EPICr2009 and CKD-EPICr2021. In validation population 2, MMB-eGFR was unbiased and displayed better precision than CKD-EPICr2009, CKD-EPICr2021 and EKFC (SD of the biases: 13.1 vs 16.5, 16.8 and 15.9 mL/min/1.73 m2). In validation population 3, MMB-eGFR had better precision and accuracy {accuracy within 30%: 75.0% [95% confidence interval (CI) 64.0-86.0] vs 51.5% (95% CI 39.0-64.3) for CKD-EPICr2009, 43.3% (95% CI 31.0-55.9) for CKD-EPICr2021, and 53.3% (95% CI 40.7-66.0) for EKFC}. Difference in bias between Black and white subjects was -2.1 mL/min/1.73 m2 (95% CI -7.2 to 3.0), vs -8.4 mL/min/1.73 m2 (95% CI -13.2 to -3.6) for CKD-EPICr2021. Conclusion: MMB-eGFR displayed better performances than equations based on demographics, and could be applied to subjects of various ethnic backgrounds.

Combining robust urine biomarkers to assess chronic kidney disease progression.

BACKGROUND: Urinary biomarkers may improve the prediction of chronic kidney disease (CKD) progression. Yet, data reporting the applicability of most commercial biomarker assays to the detection of their target analyte in urine together with an evaluation of their predictive performance are scarce. METHODS: 30 commercial assays (ELISA) were tested for their ability to quantify the target analyte in urine using strict (FDA-approved) validation criteria. In an exploratory analysis, LASSO (Least Absolute Shrinkage and Selection Operator) logistic regression analysis was used to identify potentially complementary biomarkers predicting fast CKD progression, determined as the 51CrEDTA clearance-based measured glomerular filtration rate (mGFR) decline (>10% per year) in a subsample of 229 CKD patients (mean age, 61 years; 66% men; baseline mGFR, 38 mL/min) from the NephroTest prospective cohort. FINDINGS: Among the 30 assays, directed against 24 candidate biomarkers, encompassing different pathophysiological mechanisms of CKD progression, 16 assays fulfilled the FDA-approved criteria. LASSO logistic regressions identified a combination of five biomarkers including CCL2, EGF, KIM1, NGAL, and TGF-α that improved the prediction of fast mGFR decline compared to the kidney failure risk equation variables alone: age, gender, mGFR, and albuminuria. Mean area under the curves (AUC) estimated from 100 re-samples was higher in the model with than without these biomarkers, 0.722 (95% confidence interval 0.652-0.795) vs. 0.682 (0.614-0.748), respectively. Fully-adjusted odds-ratios (95% confidence interval) for fast progression were 1.87 (1.22, 2.98), 1.86 (1.23, 2.89), 0.43 (0.25, 0.70), 1.10 (0.71, 1.83), 0.55 (0.33, 0.89), and 2.99 (1.89, 5.01) for albumin, CCL2, EGF, KIM1, NGAL, and TGF-α, respectively. INTERPRETATION: This study provides a rigorous validation of multiple assays for relevant urinary biomarkers of CKD progression which combination may improve the prediction of CKD progression. FUNDING: This work was supported by Institut National de la Santé et de la Recherche Médicale, Université de Paris, Assistance Publique Hôpitaux de Paris, Agence Nationale de la Recherche, MSDAVENIR, Pharma Research and Early Development Roche Laboratories (Basel, Switzerland), and Institut Roche de Recherche et Médecine Translationnelle (Paris, France).

Comparison of 99mTc-DTPA and 51Cr-EDTA for glomerular filtration rate measurement with the continuous infusion method.

BACKGROUND: In late 2018, the production of 51Chromium-labelled ethylenediamine tetra-acetic acid (51Cr-EDTA), a validated and widely used radio-isotopic tracer for measuring glomerular filtration rate, was halted. Technetium-99m-diethylenetriaminepentaacetic acid (99mTc-DTPA) has been validated for GFR measurement with a single bolus injection, a procedure not suitable in patients with extracellular compartment hyperhydration. In such cases, a bolus followed by continuous infusion of the tracer is required. The aim of this study was to evaluate whether 99mTc-DTPA with the infusion protocol can replace 51Cr-EDTA for GFR measurement. METHODS: We conducted a prospective single centre study during February and March 2019. All patients referred for GFR measurement received both radiotracers simultaneously: 51Cr-EDTA and 99mTc-DTPA bolus and continuous infusion were administered concomitantly through the same intravenous route. Over four and a half hours, plasma and urine samples were collected to calculate urinary and plasma clearance. RESULTS: Twenty-two patients were included (mean age 63.4 ± 17.5 years; 68% men). Mean urinary clearance of 51Cr-EDTA and 99mTc-DTPA was 52.4 ± 22.5 mL/min and 52.8 ± 22.6 mL/min, respectively (p = 0.47), with a mean bias of 0.39 ± 2.50 mL/min, an accuracy within 10% of 100% (95% CI 100; 100) and a Pearson correlation coefficient of 0.994. Mean plasma clearance of 51Cr-EDTA and 99mTc-DTPA was 54.8 ± 20.9 mL/min and 54.4 ± 20.9 mL/min, respectively (p = 0.61), with a mean bias of - 0.43 ± 3.89 mL/min, an accuracy within 10% of 77% (95% CI 59; 91) and a Pearson correlation coefficient of 0.983. CONCLUSIONS: Urinary and plasma clearance of 99mTc-DTPA can be used with the infusion protocol to measure GFR.

New developments and future prospects in the field of glomerular filtration rate estimation / Actualités et perspectives dans l'estimation du débit de filtration glomérulaire

Glomerular filtration rate (GFR) is estimated from equations based on serum or plasma concentrations of endogenous markers (creatinine and/or cystatin C), and demographic data (age, sex, ± ethnicity). These equations are accurate at the population level, but often inaccurate at the individual level. The creatinine-based Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation published in 2009 (CKD-EPIcr-2009), and the CKD-EPI equation published in 2012 based on creatinine and cystatin C, were recalibrated in 2021 to remove their dedicated race correction factors for black American subjects. All creatinine-based CKD-EPI equations overestimate true GFR in subjects younger than 30 years. The Full Age Spectrum (FAS) equation, applicable across the entire age spectrum (pediatrics to old age), solved this problem, but remained suboptimal at low GFR values. The European Kidney Function Consortium (EKFC) equation published in 2021 was an improvement of the FAS equation, which also includes the Q factor (median creatinine in the general population). EKFC is applicable across the age spectrum and is efficient at low and normal GFR values. The new creatinine-based CKD-EPI equation (CKD-EPIcr-2021) underestimates GFR in Black Americans and overestimates it in non-Black Americans. In European and African subjects, CKD-EPIcr-2021 overestimates true GFR and should not be adopted. The EKFC equation, which performs well in this population, also performs well in European Black subjects and in African subjects, provided dedicated Q factors are used.

Le débit de filtration glomérulaire (DFG) est estimé à partir d'équations prenant en compte la concentration sérique ou plasmatique de marqueurs endogènes (créatinine et/ou cystatine C) et des données démographiques (âge, sexe, ± origine ethnique). Ces équations sont justes à l'échelle populationnelle, mais fréquemment inexactes à l'échelle individuelle. L'équation Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI), basée sur la créatinine, publiée en 2009 (CKD-EPIcr-2009), et l'équation CKD-EPI de 2012, basée sur la créatinine et la cystatine C, ont été recalibrées en 2021 afin d'éliminer leurs facteurs correctifs ethniques dédiés aux sujets Noirs américains. Toutes les équations CKD-EPI basées sur la créatinine surévaluent le DFG réel chez les sujets de moins de 30 ans. L'équation Full Age Spectrum (FAS), applicable sur tout le spectre d'âge (de la pédiatrie au grand âge), résolvait ce problème, mais restait suboptimale aux valeurs basses de DFG. L'équation European Kidney Function Consortium (EKFC) publiée en 2021 est une amélioration de l'équation FAS, qui inclut également le facteur Q (créatinine médiane en population générale). Elle est applicable sur tout le spectre d'âge, et performante aux valeurs basses et normales de DFG. La nouvelle équation CKD-EPI basée sur la créatinine (CKD-EPIcr-2021) sous-évalue le DFG chez les sujets Noirs américains et le surévalue chez les non-Noirs américains. Chez les sujets européens et africains, CKD-EPIcr-2021 surévalue le DFG réel et ne doit pas être adoptée. L'équation EKFC, qui est performante dans cette population, l'est aussi chez les sujets européens Noirs et les Africains, à condition d'utiliser des facteurs Q dédiés.

Cystatin C-Based Equation to Estimate GFR without the Inclusion of Race and Sex.

BACKGROUND: The accuracy of estimation of kidney function with the use of routine metabolic tests, such as measurement of the serum creatinine level, has been controversial. The European Kidney Function Consortium (EKFC) developed a creatinine-based equation (EKFC eGFRcr) to estimate the glomerular filtration rate (GFR) with a rescaled serum creatinine level (i.e., the serum creatinine level is divided by the median serum creatinine level among healthy persons to control for variation related to differences in age, sex, or race). Whether a cystatin C-based EKFC equation would increase the accuracy of estimated GFR is unknown. METHODS: We used data from patients in Sweden to estimate the rescaling factor for the cystatin C level in adults. We then replaced rescaled serum creatinine in the EKFC eGFRcr equation with rescaled cystatin C, and we validated the resulting EKFC eGFRcys equation in cohorts of White patients and Black patients in Europe, the United States, and Africa, according to measured GFR, levels of serum creatinine and cystatin C, age, and sex. RESULTS: On the basis of data from 227,643 patients in Sweden, the rescaling factor for cystatin C was estimated at 0.83 for men and women younger than 50 years of age and 0.83 + 0.005 × (age - 50) for those 50 years of age or older. The EKFC eGFRcys equation was unbiased, had accuracy that was similar to that of the EKFC eGFRcr equation in both White patients and Black patients (11,231 patients from Europe, 1093 from the United States, and 508 from Africa), and was more accurate than the Chronic Kidney Disease Epidemiology Collaboration eGFRcys equation recommended by Kidney Disease: Improving Global Outcomes. The arithmetic mean of EKFC eGFRcr and EKFC eGFRcys further improved the accuracy of estimated GFR over estimates from either biomarker equation alone. CONCLUSIONS: The EKFC eGFRcys equation had the same mathematical form as the EKFC eGFRcr equation, but it had a scaling factor for cystatin C that did not differ according to race or sex. In cohorts from Europe, the United States, and Africa, this equation improved the accuracy of GFR assessment over that of commonly used equations. (Funded by the Swedish Research Council.).

Clinically relevant urine creatinine underestimation in the low concentration range on the Siemens Dimension Vista®.

While considerable efforts have been accomplished to standardize the measurement of plasma creatinine (PCr), urine creatinine (UCr) has not been subject to the same scrutiny. UCr is importantly used when measuring biomarkers in spot urines, to assess urine output and variable dilution of urine samples. Here, we report underestimation of Jaffe UCr measurements on the Siemens Dimension Vista® analyzer, critically affecting samples with UCr ≤2 mmol/L. We demonstrate that this error is caused by automatic urine pre-dilution by the Vista's «urine mode¼, and that UCr measured in «plasma mode¼ without pre-dilution does not present this error. In the absence of a comprehensive solution proposed by Siemens, we propose simple formulae that can be easily implemented in a laboratory to correct these low UCr measurements. Importantly, the observed UCr underestimation can significantly influence reported results for biomarkers/UCr ratios measured in spot urine. Indeed, these results can be overestimated up to +84.4 % before correction using our formulae. This can sometimes lead to misclassification according to clinical thresholds, e.g. Kidney disease: improving global outcomes (KDIGO) guidelines for urine albumin/creatinine. This highlights the need for every clinical laboratory to assess the detection limits of their assays, including for lesser-discussed parameters such as UCr. Indeed, the error we reported here may affect other urine assays performing systematic urine pre-dilution and could have significant repercussions on the clinical management of patients.

Performance of creatinine-based equations to estimate glomerular filtration rate in White and Black populations in Europe, Brazil and Africa.

BACKGROUND: A new Chronic Kidney Disease Epidemiology Collaboration equation without the race variable has been recently proposed (CKD-EPIAS). This equation has neither been validated outside USA nor compared with the new European Kidney Function Consortium (EKFC) and Lund-Malmö Revised (LMREV) equations, developed in European cohorts. METHODS: Standardized creatinine and measured glomerular filtration rate (GFR) from the European EKFC cohorts (n = 13 856 including 6031 individuals in the external validation cohort), from France (n = 4429, including 964 Black Europeans), from Brazil (n = 100) and from Africa (n = 508) were used to test the performances of the equations. A matched analysis between White Europeans and Black Africans or Black Europeans was performed. RESULTS: In White Europeans (n = 9496), both the EKFC and LMREV equations outperformed CKD-EPIAS (bias of -0.6 and -3.2, respectively versus 5.0 mL/min/1.73 m², and accuracy within 30% of 86.9 and 87.4, respectively, versus 80.9%). In Black Europeans and Black Africans, the best performance was observed with the EKFC equation using a specific Q-value (= concentration of serum creatinine in healthy males and females). These results were confirmed in matched analyses, which showed that serum creatinine concentrations were different in White Europeans, Black Europeans and Black Africans for the same measured GFR, age, sex and body mass index. Creatinine differences were more relevant in males. CONCLUSION: In a European and African cohort, the performances of CKD-EPIAS remain suboptimal. The EKFC equation, using usual or dedicated population-specific Q-values, presents the best performance in the whole age range in the European and African populations included in this study.

Chronic Lithium Therapy and Urine-Concentrating Ability in Individuals With Bipolar Disorder: Association Between Daily Dose and Resistance to Vasopressin and Polyuria.

Introduction: Lithium treatment can induce nephrogenic diabetes insipidus (NDI), but no consensus intervention is offered to date. We evaluated in these patients patterns of urine concentration and the correlates of 24-hour urine output. Methods: Prospective, single-center, observational study of 217 consecutive lithium-treated individuals, with 24-hour urine collection, desmopressin (1-deamino-arginine vasopressin [DDAVP]) concentrating test, fasting plasma vasopressin measurement (copeptin measurement in n = 119), and measured glomerular filtration rate (mGFR). Maximal urine osmolality (MaxUosm) was the highest level during the DDAVP test. Results: Of the individuals, 21% displayed polyuria (>3 l/d), but 55% displayed elevated fasting vasopressin level (>5 pg/ml). Uosm was significantly lower and urinary output and free water clearance were significantly higher in individuals treated for >10 years. MaxUosm was >600 mOsm/KgH2O in 128 patients (59%), among which vasopressin was increased in 51%, associated with higher lithium dose (950 [750-1200] vs. 800 [500-1000] mg/d, P < 0.001). All patients with lithium daily dose ≥1400 mg/d had high vasopressin levels. In multivariable analysis, 24-hour urine output was associated with higher lithium daily dose (ß 0.49 ± 0.17, P = 0.005), female sex (ß -359 ± 123, P = 0.004), daily osmolar intake (ß 2.21 ± 0.24, P < 0.001), MaxUosm (ß -2.89 ± 0.35, P < 0.001), and plasma vasopressin level (ß 10.17 ± 4.76, P = 0.03). Conclusion: Higher lithium daily dose was associated with higher vasopressin levels and higher urine output, independently of other factors. Daily osmolar intake was also associated with higher 24-hour urine output. These results suggest that controlled salt and protein intake and lithium dose might reduce polyuria in these patients.

Estimating Extracellular Fluid Volume in Healthy Individuals: Evaluation of Existing Formulae and Development of a New Equation.

Introduction: Several clinical settings require an accurate estimation of the physiologically expected extracellular fluid volume (ECFV). We aimed to analyze the performances of existing ECFV-estimating equations and to develop a new equation. Methods: The performances of 11 ECFV-estimating equations were analyzed in 228 healthy kidney donor candidates (Bichat Hospital, Paris, France) who underwent ECFV measurement using the distribution volume of 51Cr-labeled EDTA (51Cr-EDTA). An equation was developed using a penalized linear modeling approach (elastic net regression) and externally (Tenon Hospital, Paris, France, N = 142) validated. Results: Participants from Bichat (mean age 45.2 ± 12.0 years, 43.0% men) and Tenon (47.8 ± 10.3 years, 29.6% men) hospitals had a mean measured ECFV of 15.4 ± 2.8 l and 15.1 ± 2.1 l, respectively. Available ECFV-estimating formulae have highly variable precision and accuracy. The new equation incorporating body weight, height, sex, and age had better precision and accuracy than all other equations in the external validation cohort, with a median bias of -0.20 (95% CI: -0.35 to -0.05) l versus -2.63 (-2.87 to -2.42) l to -0.57 (- 0.83 to -0.40) l and 0.21 (0.12 to 0.43) l to 2.89 (2.65 to 3.11) l, for underestimating and overestimating equations, respectively, an interquartile range for the bias of 0.88 (0.70 to 1.08) l versus 0.91 (0.71 to 1.20) l to 1.93 (1.67 to 2.25) l, and an accuracy within 10% of 90.9% (83.8 to 94.4) versus 88.0% (81.0 to 92.3) to 8.5% (4.2 to 13.4). These results were consistent across subgroups defined by sex, body mass index (BMI), body surface area (BSA), age, and ethnicity. Conclusion: We developed and validated a new equation to estimate the individual reference value of ECFV, which is easily usable in clinical practice. Further validation in cohorts including individuals of extreme age and corpulence remains needed.

MRI-based kidney radiomic analysis during chronic lithium treatment.

BACKGROUND: Lithium therapy during bipolar disorder is associated with an increased risk of chronic kidney disease (CKD) that is slowly progressive and undetectable at early stages. We aimed at identifying kidney image texture features as possible imaging biomarkers of decreased measured glomerular filtration rate (mGFR) using radiomics of T2-weighted magnetic resonance imaging (MRI). METHODS: One hundred and eight patients treated with lithium were evaluated including mGFR and kidney MRI, with T2-weighted sequence single-shot fast spin-echo. Computed radiomic analysis was performed after kidney segmentation. Significant features were selected to build a radiomic signature using multivariable Cox analysis to detect an mGFR <60 ml/min/1.73 m². The texture index was validated using a training and a validation cohort. RESULTS: Texture analysis index was able to detect an mGFR decrease, with an AUC of 0.85 in the training cohort and 0.71 in the validation cohort. Patients with a texture index below the median were older (59 [42-66] vs. 46 [34-54] years, p = .001), with longer treatment duration (10 [3-22] vs. 6 [2-10] years, p = .02) and a lower mGFR (66 [46-84] vs. 83 [71-94] ml/min/1.73m², p < .001). Texture analysis index was independently and negatively associated with age (ß = -.004 ± 0.001, p < .001), serum vasopressin (-0.005 ± 0.002, p = .02) and lithium treatment duration (-0.01 ± 0.003, p = .001), with a significant interaction between lithium treatment duration and mGFR (p = .02). CONCLUSIONS: A renal texture index was developed among patients treated with lithium associated with a decreased mGFR. This index might be relevant in the diagnosis of lithium-induced renal toxicity.

Erythrocytosis associated with IgA nephropathy.

BACKGROUND: Erythrocytosis is a hematological disorder usually related to hematopoietic stem cell somatic mutations. However, unexplained erythrocytosis remains frequent. In this study, we evaluated the involvement of IgA1, a regulator of erythropoiesis also implicated in IgA nephropathy (IgAN) pathophysiology, in unexplained polycythemia/erythrocytosis (PE) of IgAN patients. METHODS: IgAN-PE patients' serum was collected, analyzed and used to study IgA1 effect on proliferation and differentiation of erythroid progenitors. Hematological parameters of transgenic mice for human alpha1 heavy chain were studied. Multicentric observational cohorts of chronic kidney disease (CKD) patients, including both native kidney diseases and renal transplants, were studied to analyze patient hemoglobin levels. FINDINGS: We retrospectively identified 6 patients with IgAN and unexplained PE. In large CKD cohorts, IgAN was associated with PE in 3.5% of patients (p<0.001 compared to other nephropathies). IgAN was an independent factor associated with higher hemoglobin levels (13.1g/dL vs 12.2 g/dL, p=0.01). During post-transplant anemia, anemia recovery was faster in IgAN patients. Elevated polymeric/monomeric IgA1 ratio as well as high Gd-IgA1 rate were observed in circulating IgA1 of the 6 IgAN-PE patients as compared with control or IgAN patients without PE. IgA1 from these patients increased the sensitivity of erythroid progenitors to Epo. In mice, we also observed an elevation of hematocrit in alpha1 knock-in mice compared to wild type controls. INTERPRETATION: These data identify a new etiology of erythrocytosis and demonstrate the role of pIgA1 in human erythropoiesis. This syndrome of IgA-related erythrocytosis should be investigated in case of unexplained erythrocytosis and renal disease. FUNDING: This work was supported by INSERM (French national institute for health and medical research), Labex GRex and Imagine Institute (Paris, France).

Kidney function monitoring in inflammatory bowel disease: The MONITORED consensus.

BACKGROUND AND AIMS: Patients with inflammatory bowel diseases (IBD) are exposed to drug-related nephrotoxicity and kidney-related extra-intestinal manifestations (EIMs). Patients should be monitored but guidance is lacking in current international recommendations. The objective of the Kidney Function Monitoring in Inflammatory Bowel Disease (MONITORED) initiative was to achieve an expert consensus about monitoring kidney function in IBD. METHODS: A literature review was first conducted. Then, an expert consensus meeting, involving 28 attendees representing French-speaking gastroenterologists and nephrologists, was held as part of an academic initiative on May 28, 2021. An anonymous Delphi process was used to discuss and vote on statements. Agreement was defined as at least 75% of participants voting for any one statement. RESULTS: Experts reached consensus on 11 criteria for referral to the nephrologist. Concerning kidney function monitoring, participants unanimously validated the use of serum creatinine with estimation of the glomerular filtration rate via the MDRD or CKD-EPI equations. A blood ionogram and a urine sample with measurement of a protein-to-creatinine ratio were also broadly agreed validated. Experts recommended performing this monitoring at IBD diagnosis, prior introducing a new treatment, and annually for EIMs screening and evaluation of treatment tolerance. An evaluation 3 months after starting mesalamine and then every 6 months was felt necessary, while for biologics an annually monitoring was deemed sufficient. CONCLUSION: The MONITORED consensus proposed guidelines on how to monitor kidney function in IBD. These recommendations should be considered in clinical practice to preserve kidney function and ensure the best approach to our patients.

Covid-19 crisis impact on the next generation of physicians: a survey of 800 medical students.

BACKGROUND: Many initiatives have emerged worldwide to handle the surge of hospitalizations during the SARS-CoV-2 pandemic. In France, the University of Paris North called on its medical students, whose status makes them integral members of the healthcare staff, to volunteer in their capacity of medical students and/or as nurses/nursing aids in understaffed intensive care units and other Covid-19 services. We attempted to evaluate their commitment, whether the pandemic affected their certainty for the medical profession and career choices, and how they scored their sadness and anxiety levels. METHODS: The University of Paris North took a weekly official census of the involvement of 1205 4th-6th year medical students during the first lockdown in France. Six weeks after the lockdown began (May 4th), an e-questionnaire was sent to 2145 2nd-6th year medical students. The survey lasted 4 weeks and documented volunteering by medical students, the association between the pandemic and certainty for their profession, their choice of medical specialty and factors that influenced sadness and anxiety scores. RESULTS: 82% of 4th-6th year medical students volunteered to continue their internship or be reassigned to COVID-19 units. Of 802 2nd-6th year students who completed the e-questionnaire, 742 (93%) volunteered in Covid-19 units, of which half acted as nurses. This engagement reinforced the commitment of 92% of volunteers to become physicians. However, at the peak of the outbreak, 17% had doubts about their ability to be physicians, while 12% reconsidered their choice of future specialty. Finally, 38% of students reported a score of 7/10 or more on the sadness scale, and 43% a score of 7/10 or more for anxiety. Neither study year nor service influenced sadness or anxiety scores. However, gender influenced both, with women scoring significantly higher than men (p < 0.0001). CONCLUSION: Medical students of the University of Paris North who made an early and unconditional commitment to help hospital staff handle the pandemic constituted a powerful healthcare reserve force during the crisis. Although the vast majority remained convinced that they want to become physicians, this experience came at a significant psychological cost, especially for women. Alleviating this cost would improve future crisis responses.