Marie Courbebaisse

BACKGROUND: The Chronic Kidney Disease in Children Study (CKiD) equation for children and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation for adults are recommended serum creatinine (SCr)-based calculations for estimating glomerular filtration rate (GFR). However, these equations, as well as their combination, have limitations, notably the problem of implausible changes in GFR during the transition from adolescence to adulthood and overestimation of GFR in young adults. The full age spectrum (FAS) equation addresses these issues but overestimates GFR when SCr levels are low. OBJECTIVE: To develop and validate a modified FAS SCr-based equation combining design features of the FAS and CKD-EPI equations. DESIGN: Cross-sectional analysis with separate pooled data sets for development and validation. SETTING: = 13) with measured GFR available. PATIENTS: 11 251 participants in 7 studies (development and internal validation data sets) and 8378 participants in 6 studies (external validation data set). MEASUREMENTS: Clearance of an exogenous marker (reference method), SCr level, age, sex, and height were used to develop a new equation to estimate GFR. RESULTS: ] in adults) across the FAS (2 to 90 years) and SCr range (40 to 490 µmol/L [0.45 to 5.54 mg/dL]) and with fewer estimation errors exceeding 30% (6.5% [CI, 3.8% to 9.1%] in children and 3.1% [CI, 2.5% to 3.6%] in adults) compared with the CKiD and CKD-EPI equations. LIMITATION: No Black patients were included. CONCLUSION: The new EKFC equation shows improved accuracy and precision compared with commonly used equations for estimating GFR from SCr levels. PRIMARY FUNDING SOURCE: Swedish Research Council (Vetenskapsrådet).

Both acute and chronic dehydration can have important implications for human behaviour and health. Young children, non-autonomous individuals and the elderly are at a greater risk of dehydration. Mild hypertonic dehydration could be related to less efficient cognitive and physical performance and has been reported to be associated with frequently occurring pathological conditions, especially nephrolithiasis. The assessment of hydration status in a large sample appears to be of interest for conducting epidemiological and large clinical studies aimed at improving preventive and curative care. Especially in large-population studies, methods that are used have to be accurate, cheap, quick and require no technical expertise. Body weight change is widely used to determine acute hydration changes, but seems to be insufficiently accurate in longitudinal studies. Bioimpedance analysis methods enable the assessment of total body water content, but their use is still under debate. Because plasma osmolality directly reflects intracellular osmolality, it constitutes a good marker to assess acute hydration changes, but not chronic hydration status because it changes constantly. Moreover, venepuncture is considered to be invasive and is not suitable for a large-sample study, especially in children. Urinary markers appear to be good alternatives for assessing hydration status in large populations. Collection of urine samples is non-invasive and cheap. High technical expertise is not required to perform urinary marker measurements and these measurements can be carried out quickly. Thus, methods based on urinary markers are very well suited for field studies. Urine colour is probably the least sensitive marker despite its high specificity. Urine osmolality and especially urine specific gravity could be easily used for determining hydration status in large-sample studies.

• Vitamin D deficiency is very common. • Randomised controlled trials showed that vitamin D decreases acute respiratory infections (ARIs). • Vitamin D deficiency is an easily modifiable factor of ARIs. • Daily vitamin D supplementation with moderate doses is safe and cheap. • Even a small decrease in COVID-19 infections would easily justify this intervention.

BACKGROUND AND OBJECTIVES: Cystinuria is an autosomal recessive disorder affecting renal cystine reabsorption; it causes 1% and 8% of stones in adults and children, respectively. This study aimed to determine epidemiologic and clinical characteristics as well as comorbidities among cystinuric patients, focusing on CKD and high BP. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: This retrospective study was conducted in France, and involved 47 adult and pediatric nephrology and urology centers from April 2010 to January 2012. Data were collected from 442 cystinuric patients. RESULTS: Median age at onset of symptoms was 16.7 (minimum to maximum, 0.3-72.1) years and median diagnosis delay was 1.3 (0-45.7) years. Urinary alkalinization and cystine-binding thiol were prescribed for 88.8% and 52.2% of patients, respectively, and 81.8% had at least one urological procedure. Five patients (1.1%, n=4 men) had to be treated by dialysis at a median age of 35.0 years (11.8-70.7). Among the 314 patients aged ≥16 years, using the last available plasma creatinine, 22.5% had an eGFR≥90 ml/min per 1.73 m(2) (calculated by the Modification of Diet in Renal Disease equation), whereas 50.6%, 15.6%, 7.6%, 2.9%, and 0.6% had an eGFR of 60-89, 45-59, 30-44, 15-29, and <15, respectively. Among these 314 patients, 28.6% had high BP. In multivariate analysis, CKD was associated with age (odds ratio, 1.05 [95% confidence interval, 1.03 to 1.07]; P<0.001), hypertension (3.30 [1.54 to 7.10]; P=0.002), and severe damage of renal parenchyma defined as a past history of partial or total nephrectomy, a solitary congenital kidney, or at least one kidney with a size <10 cm in patients aged ≥16 years (4.39 [2.00 to 9.62]; P<0.001), whereas hypertension was associated with age (1.06 [1.04 to 1.08]; P<0.001), male sex (2.3 [1.3 to 4.1]; P=0.003), and an eGFR<60 ml/min per 1.73 m(2) (2.7 [1.5 to 5.1]; P=0.001). CONCLUSIONS: CKD and high BP occur frequently in patients with cystinuria and should be routinely screened.