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See detailCalibration and precision of serum creatinine and plasma cystatin C measurement: impact on the estimation of glomerular filtration rate
DELANAYE, Pierre ULg; CAVALIER, Etienne ULg; Cristol, Jean-Paul et al

in Journal of Nephrology (2014), 27(5), 467-75

Serum creatinine (SCr) is the main variable for estimating glomerular filtration rate (GFR). Due to interassay differences, the prevalence of chronic kidney disease (CKD) varies according to the assay ... [more ▼]

Serum creatinine (SCr) is the main variable for estimating glomerular filtration rate (GFR). Due to interassay differences, the prevalence of chronic kidney disease (CKD) varies according to the assay used, and calibration standardization is necessary. For SCr, isotope dilution mass spectrometry (IDMS) is the gold standard. Systematic differences are observed between Jaffe and enzymatic methods. Manufacturers subtract 0.30 mg/dl from Jaffe results to match enzymatic results (‘compensated Jaffe method’). The analytical performance of enzymatic methods is superior to that of Jaffe methods. In the original Modification of Diet in Renal Disease (MDRD) equation, SCr was measured by a Jaffe Beckman assay, which was later recalibrated. A limitation of this equation was an underestimation of GFR in the high range. The Chronic Kidney Disease Epidemiology (CKD-EPI) consortium proposed an equation using calibrated and IDMS traceable SCr. The gain in performance was due to improving the bias whereas the precision was comparable. The CKD-EPI equation performs better at high GFR levels (GFR[60 ml/ min/1.73 m2). Analytical limitations have led to the recommendation to give a grade ([60 ml/min/1.73 m2) rather than an absolute value with the MDRD equation. By using both enzymatic and calibrated methods, this cutoff-grade could be increased to 90 ml/min/1.73 m2 (with MDRD) and 120 ml/min/1.73 m2 (with CKD-EPI). The superiority of the CKD-EPI equation over MDRD is analytical, but the precision gain is limited. IDMS traceable enzymatic methods have been used in the development of the Lund– Malmo¨ (in CKD populations) and Berlin Initiative Study equations (in the elderly). The analytical errors for cystatin C are grossly comparable to issues found with SCr. Standardization is available since 2011. A reference method for cystatin C is still lacking. Equations based on standardized cystatin C or cystatin C and creatinine have been proposed. The better performance of these equations (especially the combined CKD-EPI equation) has been demonstrated. [less ▲]

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See detailHypervitaminémie B12 : un piège diagnostique pour le biologiste et pour le clinicien ?
LUYCKX, Françoise ULg; Texeira, J; VALDES SOCIN, Hernan Gonzalo ULg et al

in Abstract book - Annales d'Endocrinologie : 31ème Congrès de la Société Française d'Endocrinologie, Lyon 5-8 novembre 2014 (2014, October)

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See detailDosage de la vitamine D: Point de vue du Biologiste
CAVALIER, Etienne ULg

Conference (2014, September 27)

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See detailEpidémiologie de la lithiase urinaire en Province de Liège
GADISSEUR, Romy ULg; Castiglione, Vincent ULg; JOURET, François ULg et al

in Néphrologie & Thérapeutique (2014, September), 10(5), 270

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See detailDephosphorylated-uncarboxylated Matrix Gla protein concentration is predictive of vitamin K status and is correlated with vascular calcification in a cohort of hemodialysis patients.
DELANAYE, Pierre ULg; KRZESINSKI, Jean-Marie ULg; Warling, X et al

in BMC Nephrology (2014), 15

Background: Matrix Gla protein (MGP) is known to act as a potent local inhibitor of vascular calcifications. However, in order to be active, MGP must be phosphorylated and carboxylated, with this last ... [more ▼]

Background: Matrix Gla protein (MGP) is known to act as a potent local inhibitor of vascular calcifications. However, in order to be active, MGP must be phosphorylated and carboxylated, with this last process being dependent on vitamin K. The present study focused on the inactive form of MGP (dephosphorylated and uncarboxylated: dp-ucMGP) in a population of hemodialyzed (HD) patients. Results found in subjects being treated or not with vitamin K antagonist (VKA) were compared and the relationship between dp-ucMGP levels and the vascular calcification score were assessed. Methods: One hundred sixty prevalent HD patients were enrolled into this observational cohort study, including 23 who were receiving VKA treatment. The calcification score was determined (using the Kauppila method) and dp-ucMGP levels were measured using the automated iSYS method. Results: dp-ucMGP levels were much higher in patients being treated with VKA and little overlap was found with those not being treated (5604 [3758; 7836] vs. 1939 [1419; 2841] pmol/L, p <0.0001). In multivariate analysis, treatment with VKA was the most important variable explaining variation in dp-ucMGP levels even when adjusting for all other significant variables. In the 137 untreated patients, dp-ucMGP levels were significantly (p < 0.05) associated both in the uni- and multivariate analysis with age, body mass index, plasma levels of albumin, C-reactive protein, and FGF-23, and the vascular calcification score. Conclusion: We confirmed that the concentration of dp-ucMGP was higher in HD patients being treated with VKA. We observed a significant correlation between dp-ucMGP concentration and the calcification score. Our data support the theoretical role of MGP in the development of vascular calcifications. We confirmed the potential role of the inactive form of MGP in assessing the vitamin K status of the HD patients. [less ▲]

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See detailInter-method variability in bone alkaline phosphatase measurement : clinical impact on the management of dialysis patients
CAVALIER, Etienne ULg; Souberbielle, Jean-Claude; GADISSEUR, Romy ULg et al

in Clinical Biochemistry (2014), 47(13-14), 1227-30

BACKGROUND: Bone-specific alkaline phosphatase (BAP) is now recommended to assess bone turnover in hemodialysis (HD) patients. However, little is known about potential variability between methods ... [more ▼]

BACKGROUND: Bone-specific alkaline phosphatase (BAP) is now recommended to assess bone turnover in hemodialysis (HD) patients. However, little is known about potential variability between methods available to measure BAP. METHODS: We measured BAP in 76 HD patients with six different assays (Beckman-Coulter Ostase IRMA, Beckman-Coulter Ostase Access, IDS iSYS Ostase, IDS Ostase enzyme immunoassay, DiaSorin Liaison Ostase and Quidel MicroVue BAP). RESULTS: We observed a high correlation between all the assays ranging from 0.9948 (IDS iSYS vs. IDS EIA) to 0.9215 (DiaSorin Liaison vs. Quidel MicroVue). However, using the regression equations, the equivalent concentration of a Beckman-Coulter Access value of 10μg/L can range from 7.7 to 14.4μg/L and of 20μg/L can range from 16.9 to 27.9μg/L with other assays. According to Beckman-Coulter Access, 13%, 50% and 37% of the patients presented BAP values ≤10, between 10 and 20 and ≥20μg/L, respectively. Discrepancies are observed when other assays are used (concordance from 10 to 100%). CONCLUSIONS: Analytical problems leading to inter-method variation should be overcome to improve the usefulness of this marker in clinical practice. According to correlation results, recalibration of BAP assays is necessary but should not be a major issue. [less ▲]

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See detailStandardization of DiaSorin and Roche automated third generation PTH assays with an international standard: impact on clinical populations
CAVALIER, Etienne ULg; DELANAYE, Pierre ULg; LUKAS, Pierre ULg et al

in Clinical Chemistry & Laboratory Medicine (2014), 52(8), 1137-41

Background: Standardization of parathyroid hormone (PTH) assays is a major issue, especially in hemodialyzed (HD) patients. Two automated third generation PTH assays (Roche Elecsys and DiaSorin Liaison ... [more ▼]

Background: Standardization of parathyroid hormone (PTH) assays is a major issue, especially in hemodialyzed (HD) patients. Two automated third generation PTH assays (Roche Elecsys and DiaSorin Liaison) are now available. These assays are specific for the (1-84) PTH and do not cross-react with the (7-84) fragment, contrary to second generation (intact) assays. We aimed to calibrate the two methods against the WHO International PTH Standard (IS) 95/646 to see if the two assays could provide comparable results in a population of healthy subjects, HD patients and patients suffering from primary hyperparathyroidism (PHP). Methods: We selected 79 healthy subjects and two populations of patients presenting PTH disorders: 56 HD and 27 PHP patients. We reconstituted the IS in a pool of human serum containing undetectable levels of 1-84 PTH and prepared 13 serum standards ranging from 0 to 2000 pg/mL. The standards were run on the two instruments to calibrate the assays on the IS. The different populations were run before and after restandardization. Results: As these kits were differently calibrated, the results obtained after restandarization were significantly different. Restandardization process improved concordance between assays and, taking the analytical variability of the two kits into account, the results could be considered to be similar. Conclusions: Restandardization of automated third generation PTH assays with the WHO 1-84 PTH Standard significantly reduces inter-method variability. Reference ranges and raw values are totally transposable from one method to the other in healthy subjects, but also in diseased patients, e.g., with HD or those suffering from PHP. [less ▲]

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See detailEvaluation of circulating irisin levels in healthy young individuals after a single 100,000 IU vitamin D dose.
CAVALIER, Etienne ULg; Mismetti, Valentine; Souberbielle, Jean-Claude

in Annales d'Endocrinologie (2014), 73(3), 162-164

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See detailGalectin-3: a new promising cardiac biomarker in sports endurance?
LE GOFF, Caroline ULg; Devaux, Séverine; BREVERS, Eric ULg et al

in Cardiovascular Research (2014, July), 103(Supplement 1), 255

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See detailBone markers in patients with CKD
CAVALIER, Etienne ULg

Conference (2014, June 26)

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See detailStandardisation of 25(OH)-vitamin D assays: beware of limitations
CAVALIER, Etienne ULg

Conference (2014, June 24)

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See detailURINARY AND SALIVARY CORTISOL IN LIQUID CHROMATOGRAPHY–TANDEM MASS SPECTROMETRY: METHOD VALIDATION AND EXPECTED VALUES DETERMINATION
LE GOFF, Caroline ULg; DELCOUR, Sandra ULg; PEETERS, Stéphanie ULg et al

in Clinical Chemistry & Laboratory Medicine (2014, June), 52(Special Suppl), 1241

BACKGROUND: Cortisol measurement is useful in evaluation of Cushing syndrome, adrenal insufficiency, mineralocorticoid excess and congenital adrenal hyperplasia. We developed a liquid ... [more ▼]

BACKGROUND: Cortisol measurement is useful in evaluation of Cushing syndrome, adrenal insufficiency, mineralocorticoid excess and congenital adrenal hyperplasia. We developed a liquid chromatography–tandem mass spectrometry (LCMS/MS) method for salivary and urinary cortisol and we determined the 95th percentile (p95) for the urinary and salivary cortisol. We compared them to the Mayo Clinic expected values. METHODS: Saliva at 8 am and 11 pm and 24h urine were obtained from 32 healthy (22 female, 34.3±9.3 yo) volunteers. We performed validation with the enoval software (Arlenda, Belgium). For the validation, we used water or urine with spiked known amounts of cortisol for the CORS and CTU respectively. For the CORS, samples were centrifuged, deuterium labelled cortisol was added as internal standard and the protein precipated by acetonitril. The supernatant was evaporated, dissolved in methanol acidified with acetic acid and analyzed by LCMS/MS. For CTU, samples were centrifuged, deuterium labelled cortisol was added as internal standard and diluted by the ammonium acetate and analyzed by LCMS/MS. At the Mayo Clinic, the expected values were 1-7.5 μg/L (7 a.m-9 a.m) and <1 μg/L (11-12 p.m) for CORS and 3.5-45 μg/24h (<18yo) for CTU. RESULTS: For the CTU, the with-in run did not exceed 3% (0.4-3%) and the between-run did not exceed 3.1% (0.4-3.1%) for 1.5-750 μg/L. The limit of quantification was 1.5 μg/L. The linearity was good between 1.5 and 750 μg/L. The recovery is 97.9±2.2% (95%CI for the mean: 92.4-101.1%). For the CORS, the with-in run and between run did not exceed 8% (1.9-8%) for 1.15-8.65 μg/L. The limit of quantification was 1.15 μg/L. The analyse presents a good linearity between 1.15 and 8.65 μg/L. The recovery is 99.9±2.9% (95%CI for the mean: 94.2-108.7%). The p95 for the CTU according to the CLSI C28-A3 was 33 μg/24h, and for the CORS was 5.42 μg/L at 8 am and 0.7 μg/L at 12 pm. CONCLUSIONS: Our developed method in liquid chromatography tandem mass spectrometry was validated for the measurement of urinary and salivary cortisol. Our findings indicate that the proposed analytical methods were suitable for routine purposes and useful in many pathological conditions.The expected values confirm these defined by the Mayo Clinic. [less ▲]

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See detailEvaluation of troponin T on AQT90 Flex and COBAS 8000 as a rule in/out tool in an emergency ward
LE GOFF, Caroline ULg; EVRARD, Séverine ULg; BREVERS, Eric ULg et al

in Clinical Chemistry & Laboratory Medicine (2014, June), 52(Special Suppl), 510

BACKGROUND: Troponin measurement is the gold standard for diagnosis of Acute Myocardial Infarction (AMI). Troponin (highly sensitive (hs), T or I) is measured by immunochemistry instrument or by Point of ... [more ▼]

BACKGROUND: Troponin measurement is the gold standard for diagnosis of Acute Myocardial Infarction (AMI). Troponin (highly sensitive (hs), T or I) is measured by immunochemistry instrument or by Point of Care (POCT). POCT can be useful in emergency lab or ward for a faster diagnosis of patients with chest pain. Our study compared analytical performance of a POCT AQT90 Flex (Radiometer Medical) (AQT) and TnThs Cobas 8000 (Roche Diagnostics) (Cobas). We also compared the clinical performance of both methods at recommended cut-off (14 ng/L for Cobas and 30 ng/ L for AQT). METHODS: We selected 104 patients (296 samples) (range: 6-13822 ng/L) admitted in the Emergency ward for which at least 1 troponin determination (Cobas 8000) had been re-quested in the past 24 hours according to rule in/out procedure applied by this ward. Samples were then measured with the AQT. Inter-assay CV was maximum 8.6% and 9.6% for Cobas and AQT respectively. The cut-off defined as the 99th percentile for Roche was 14 ng/L and the recommended decision threshold value was 30 ng/L for Radiometer. Retrospective analysis of final diagnostic was obtained for all participants: we considered as “true positive” patients for whom a final diagnostic was ST segment-Elevation Myocardial Infarction (STEMI) or non STEMI (NSTEMI). RESULTS: On the whole range of measure, the 2 methods showed a good correlation (r2=0.98). Regression equation was Cobas = 0.98 AQT + 31 ng/L (95%CI of the intercept: (26.7;37.7) and 95% CI of the slope (0.96;1)). When we stratified, for the values <54 ng/L, the equation became Cobas = 0.52 AQT +1.1 ng/L (95%CI of the intercept: (-4.8;5.5) and 95% CI of the slope (0.39;0.69)). Bland and Altman plot did not show any bias. At admission [2-7 hours], 78 (81%) of admitted patients were finally considered as AMI, sensitivity was 92 % [96%] for Cobas and 78% [91%] for AQT. Specificity was 15% for Cobas (cut-off 14ng/L) or 73% (cut-off 54 ng/L) and 76% for AQT. CONCLUSIONS: Overall, there was a good correlation between the 2 methods. However, using a cut-off of 14 ng/L for Cobas is questionable for a rule in/out procedure in an emergency ward. Using 54 ng/L for Roche and 30 ng/L for AQT would have led to the best discrimination between patients presenting AMI or not. [less ▲]

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See detailSUITABILITY OF 24,25(OH)2 VITAMIN D3 DETERMINATION WITH AN ADAPTED VERSION OF THE CHROMSYSTEMS® MASSCHROM® 25-OH-VITAMIN D3/D2– LC-MS/MS KIT
SCHLECK, Marie-Louise ULg; NETCHACOVITCH, Matthieu ULg; CRINE, Yannick ULg et al

in Clinical Chemistry & Laboratory Medicine (2014, June), 52(Special Suppl), 1235

BACKGROUND: The enzym CYP24A1 catalyses the conversion of 25(OH)D3 in 24,25(OH)2D3. Recently, loss-of-function mutation of CYP24A1 has been identified in idiopathic infantile hypercalcemia (IIH). This ... [more ▼]

BACKGROUND: The enzym CYP24A1 catalyses the conversion of 25(OH)D3 in 24,25(OH)2D3. Recently, loss-of-function mutation of CYP24A1 has been identified in idiopathic infantile hypercalcemia (IIH). This genetic defect can be highlighted by high 1,25(OH)2D3 and undetectable 24,25(OH)2D3 levels. 24,25(OH)2D3 is also known to interfere with 25(OH)D3 determinations with immunoassays, leading to an overestimation of the 25(OH)D3 concentrations. We adapted the MassChrom kit on the AB SCIEX TQ 5500 in order to systematically provide, next to 25(OH)D3, 25(OH)D2 and C3 epimer, the concentrations of 24,25(OH)2D3. The aim of this study was to evaluate the performance of 24,25(OH)2D3 determination with this modified method. We also wanted to establish the reference value of 24,25(OH)2D3. METHODS: We modified the Chromsystems MassChrom method by adding the 24,25(OH)D3 correspondent transitions and performed a calibration by spiking known amounts of 24.25(OH)2D3. The LOQ was determined with 10 concentration levels of 24,25(OH)2D3. We selected 92 healthy children (40 girls; 2.4±1.51 years) presenting normal calcium levels (2.49±0.13mmol/l) to determine the 95th percentile (p95). RESULTS: The 24,25(OH)2D3 LOQ was 4.7 ng/ml. 85.9% of our subjects were below this LOQ. The p 95 for the 24,25(OH)2D3, according to the CLSI C28-A3, was <6.2 ng/ml. The average serum concentrations (mean±SD) of 25(OH)D3 and 3-epi-25(OH)D3 were 24.48±10.22ng/ml and 2.07±1.86 ng/ml respectively. The 24,25(OH)2D3 levels (r2=0.64) correlated with the 25(OH)D3 levels. CONCLUSIONS: Our adapted method from Chromsystems Vitamin D determination is available to quantify 24,25(OH)2D3. In this context, this method is able to determine high levels of 24,25(OH)2D3 that can possibly cross react with immunoassays. However, as the LOQ was not low enough, we couldn’t establish correct reference value for 24,25(OH)2D3. A derivatization step in the sample preparation would be interesting to improve the sensibility of the method. [less ▲]

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See detailCan we use circulating biomarkers to monitor bone turnover in CKD haemodialysis patients? Hypotheses and facts
DELANAYE, Pierre ULg; Souberbielle, Jean-Claude; Lafage-Proust, Marie-Hélène et al

in Nephrology Dialysis Transplantation (2014), 29(5), 997-1004

Assessing bone turnover is a key diagnostic tool in the global management of chronic kidney disease-mineral and bone disorder (CKD-MBD). Since bone biopsy is invasive and cannot be repeated in clinical ... [more ▼]

Assessing bone turnover is a key diagnostic tool in the global management of chronic kidney disease-mineral and bone disorder (CKD-MBD). Since bone biopsy is invasive and cannot be repeated in clinical practice and because bone histomorphometry is less available due to the lack of specialized laboratories, we will focus on potential biomarkers used to assess and monitor bone turnover. After briefly reviewing the pathophysiology of bone turnover in CKD and haemodialysis patients, we will focus on the strengths and limitations of the now recommended biomarkers, i.e. parathormone and bone-specific alkaline phosphatase. We will consider the clinical and also the biological aspects of the topic and also insist on the use of these biomarkers for the monitoring, and the follow-up of the turnover in haemodialysis subjects. Finally, we will discuss some of the most promising, but still not recommended, emerging biomarkers. [less ▲]

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