X-linked hypophosphatemia, obesity and arterial hypertension: data from the XLH21 study.

BACKGROUND: The underlying mechanisms of obesity in X-linked hypophosphatemia (XLH) are not known. We aimed to evaluate whether FGF21, an endocrine FGF involved in the regulation of carbohydrate-lipid metabolism, could be involved. METHODS: We performed a prospective multicenter cross-sectional study comparing FGF23, Klotho, and FGF21 levels in teenagers with XLH compared to healthy controls (VITADOS cohort) after matching for age, gender, and puberty. Non-parametric tests were performed (results presented as median (min-max)). RESULTS: A total of 40 XLH teenagers (n = 20 Standard Of Care, SOC, n = 20 burosumab) were included. While patients receiving burosumab displayed increased BMI as compared to patients receiving SOC, systolic blood pressure expressed as percentile was progressively and significantly lower when comparing the three groups: 77 (4-99) in SOC, 47 (9-98) in burosumab, and 28 (1-94) in controls (p = 0.007). When compared to patients receiving SOC, patients receiving burosumab displayed significantly increased phosphate and 1,25(OH)2D levels. We found increased Klotho levels in patients receiving burosumab. No differences were found for either carbohydrate-lipid biomarkers or FGF21 between the three groups. A total of 21 XLH patients (53%) had insulin resistance (HOMA > 2.4, N = 10 SOC, N = 11 burosumab). CONCLUSION: FGF21 does not explain obesity/overweight in XLH. Of note, this study was performed in France in 2018-2019, early after the approval authorizing burosumab only in case of severe XLH despite SOC. As such, the data on systolic blood pressure highlighting a possible impact of burosumab to decrease blood pressure as well as increase Klotho levels deserve further studies given their potential effect on long-term cardiovascular risk. A higher resolution version of the Graphical abstract is available as Supplementary information.

[Eosinophiluria: accreditation with establishment of an inter-laboratories exchange]. / Éosinophilurie : accréditation avec mise en place d'un échange inter-laboratoires.

Eosinophiluria corresponds to search eosinophils in urine. These are normally absent in urine, their presence could be associated with different clinical conditions affecting kidney or urinary tract. This analysis of medical biology laboratory listed in the French Nomenclature of acts of medical biology has to be validated according to norm NF EN ISO 15189. The principle of eosinophiluria method is based on eosinophils quantification by optical microscopy in a urine sample (urination) after staining. The aim of this article is to provide to biologists the eosinophiluria's clinical interest, but also bibliographic, technical and practical elements that can help them to establish eosinophiluria in their laboratories. The method validation elements were described for each item of SH Form 43. They include the analysis risks study, inter-operator variability, uncertainties, measurement range, comparison of methods based on the comparison of two staining, interferences, robustness, reliability of reagents, reference interval. Regarding accuracy, in absence of external quality assessment for this analysis, an inter-laboratory exchange has been set up in accordance with the requirements of the norm. Its organization is described. The performance of eosinophiluria was verified, recalling the importance of the pre-analytical conditions and the quality of staining. All of these data are presented and led the accreditation of eosinophiluria in our laboratory.

Assessment of mineral and bone biomarkers highlights a high frequency of hypercalciuria in asymptomatic healthy teenagers.

AIM: Assessment of mineral metabolism is complex in paediatrics. METHODS: We assessed the evolution of the main mineral and bone biomarkers (total/bone alkaline phosphatase ALP/BAP, ß-crosslaps, osteocalcin, sclerostin, C-terminal and intact FGF23) in 100 healthy teenagers (10-18 years, 50 boys). RESULTS: At a mean age of 13.7 ± 2.2 years, phosphatemia, tubular phosphate reabsorption, ALP and BAP significantly decreased along puberty in both genders, whilst parathyroid hormone (PTH), 25-vitamin D (25D), FGF23, plasma calcium and urinary calcium were not modified. In girls, osteocalcin, ß-crosslaps and sclerostin significantly decreased at the end of puberty. Calciuria above the crystallisation threshold (>3.8 mmol/L) and urinary calcium/creatinine ratio >0.7 mmol/mmol were found in 39% and 6% of subjects, respectively. Multivariable analyses showed that renal function and PTH were significant predictors of calciuria and urinary calcium/creatinine, whilst 25D remained a predictor only of urinary calcium/creatinine ratio. CONCLUSION: Using the most recent assays, this study provides data for mineral/bone biomarkers across puberty and highlights the risk of hyper-calciuria in apparent asymptomatic healthy teenagers, not related to calcium intake but rather to 25D. Future studies are required to dissect the underlying mechanisms increasing calciuria and prevent nephrolithiasis as early as during childhood.

Urinary albumin measurement methods.

The quantification of urine albumin is a common practice in Medical Biology laboratories. It allows the assessment of renal injury in common pathologies and many studies have confirmed its role in the diagnosis and prognosis of these disorders. The physicochemical characteristics of albumin in the urine, very different from those in the blood, do not allow the use of the same standardized assay techniques for the blood albumin determination and make it difficult its quantification. Indeed, because of a physiological fragmentation phenomenon, urinary albumin is present in the urine as various small specific peptides. We will present here the main methods of determination of albumin in the urine, which are immuno-turbidimetric and immuno-nephelometric methods, high performance liquid chromatography with steric exclusion and liquid chromatography coupled with mass spectrometry. Currently, immunoanalysis techniques are the most used and are not standardized; large bias can be found between the different kits. This observation calls for a standardization of its determination in the urine.

New-generation thyroglobulin assay: performance and implications for follow-up of differentiated thyroid carcinoma.

OBJECTIVES: Differentiated thyroid cancer (DTC) requires long-term follow-up by serum thyroglobulin assay and cervical ultrasound, due to the risk of recurrence. Guidelines recommend basal assay under hormone therapy at 3 months, repeated at 6-12 months post-surgery, with or without associated isotopic ablation, after stimulation by recombinant human TSH to improve assay sensitivity. It was hypothesized that a new-generation assay kit with lower limits of detection and quantification would improve the sensitivity of the basal assay, enhance detection of premature recurrence and decrease the rate of false-negatives, thereby avoiding the need for the complementary stimulation test. MATERIAL AND METHODS: A validation study of the second-generation thyroglobulin serum assay was performed in the laboratory of the Lyon Sud Hospital Centre (Lyon, France), with comparison to stimulation test results. Low-concentration serum pools were constituted, including patients followed for stage I to III DTC for whom basal and post-stimulation samples were available in the serum bank. RESULTS: The new assay proved robust and reliable, with good correlation with the technique presently used in the Lyon hospitals. None of the 54 patients showed false-negative results, which was the objective of our choice of threshold, and 5 were false-positive, for thyroglobulin thresholds of 0.1µg/L at baseline and 1.0µg/L post-stimulation. Positive and negative predictive values were 100% and 87.8% respectively. CONCLUSION: These results allow an improvement in the follow-up algorithm for DTC, replacing the stimulation test by the new-generation thyroglobulin assay in post-therapeutic assessment.

[Focus on preanalytics for Down's syndrome screening during first trimester of pregnancy]. / Dépistage de la trisomie 21 par les marqueurs sériques maternels au premier trimestre Aspect pré-analytique.

The aim of the study is to specify the pre-analytical conditions required for Down's syndrome screening in first trimester by maternal serum markers. The concentration variation of both markers, hCGß and PAPP-A, was analyzed at room temperature, at 4°C and during freezing-thawing cycles. Serum can be kept during 72h between 2 and 8°C with an acceptable bias of 5% for each marker. It can also undergo three freezing-thawing cycles without any variation of results. Preservation at room temperature (between 20 and 25°C) requires an analysis within 24h. From this study, writing recommendations enable to give a precise frame to pre-analytical processing and transport of blood samples, in a field where variations can lead to heavy therapeutic decisions.

Comparison of anti-CCP autoantibodies measurement by ELISA and a bead-based assay in a large patient cohort.

OBJECTIVES: The aims of our study were to compare in a cohort of 705 patients the diagnostic performance of two tests to detect autoantibodies to cyclic citrullinated peptides (CCP) and to determine whether a bead-based assay within a multiplex flow immunoassay (MFA) can be used instead of an enzyme linked immunosorbent assay (ELISA) technique in routine practice. DESIGN AND METHODS: Six hundred and thirty patients with rheumatic symptoms and 75 patients with systemic lupus erythematosus (SLE) were tested for anti-CCP autoantibodies using two techniques: ELISA (Inova) and MFA (BioPlex, Bio-Rad). RESULTS: Using kappa coefficient, there was an excellent agreement between ELISA and MFA when comparing 630 patients with rheumatic symptoms (κ coefficient, 0.82). In this cohort 174 patients were identified as suffering from RA, while 456 patients suffered from other diseases. Sensitivity and specificity values of anti-CCP autoantibodies for RA were 70.7% and 92.3% for ELISA and 64.4% and 92.8% for MFA. The positive and negative predictive values were 77.4% and 89.2% for ELISA and 77.2% and 87.2% for MFA, respectively. There were no differences in the diagnostic performances between the two assays (Z=0.67). The specificity values of anti-CCP autoantibodies analysing patients with SLE were 97.3% with MFA and 96% with ELISA with an excellent agreement between the methods (98.7%; κ coefficient, 0.79). CONCLUSION: Concordance between ELISA and MFA is high in routine practice. Overall, MFA is a powerful tool for rapid assessment of anti-CCP autoantibodies and can replace the ELISA technique, which could be used as a second-line test in some cases.