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Néphrologie & Thérapeutique

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Chronic kidney failure and biotin: A combination inducing unusual results in thyroid and parathyroid investigations, report of 2 cases Volume 13, issue 7, Décembre 2017

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Authors

Introduction

Protein-energy wasting (PEW) is a strong predictive factor for morbidity and mortality in haemodialysis (HD) patients. However, there is no consensus for its assessment. The present study aimed to assess the nutritional status of patients on chronic HD by use of different nutritional assessment parameters, and at verifying which can identify the greatest number of HD patients with PEW. Also, to investigate predictors of nutritional status in a haemodialysis center in Morocco.

Patients and methods

This is a cross-sectional analysis performed on 126 patients aged 44.82±14.01 years, undergoing maintenance HD in the Department of nephrology of the university hospital centre of Casablanca, Morocco. Energy and nutrients intake assessment was obtained by a three-day period food recall. Biochemical parameters, bioelectric impedance analysis, and subjective global assessment (SGA), have been performed to assess nutritional status.

Results

According to SGA the prevalence of PEW was 74.62%. However, when using the ISRMN malnutrition criteria only 36.50% of the patients were diagnosed with PEW. Pearson correlation showed a negative association between the degree of malnutrition evaluated by SGA and serum prealbumin (r=−0.54; P=0.0001), serum albumin (r=−0.50; P=0.001), energy (r=−0.34; P=0.002), protein intake (r=−0.41; P=0.0001), and a significant positive correlation with CRP (r=0.65; P=0.0001) was determined, but not with anthropometric measurements nor lipids profile. The areas under the receiver operating characteristic curve were 0.841 (95% CI: 0.751–0.932) for serum prealbumin, and 0.737 (95% CI: 0.634–0.840) for serum albumin.

Conclusion

Our results showed a high prevalence of PEW among Haemodialysis patients. Also, our findings suggest that SGA, serum albumin and prealbumin may be relative appropriate and practical markers for assessing nutritional status in HD patients.

Purpose

Acetate in hemodialysis solutions exerts inflammatory, vasodilatatory and cardio-depressive effects. Citrate has been proposed as an optimal substitute. The aim of the present trial was the comparison of the hemodynamic and biological parameters on a group of patients dialysed consecutively with 4 acetate-free haemodialysis techniques.

Methods

In a prospective crossover manner, we measured the hemodynamic and biological effects of four acetate-free hemodialysis methods: he acetate-free biofiltration with variable potassium (AFBK) and three methods with a citrate buffer: onventional hemodialysis (HD), on-line hemodiafiltration (HDF) and on-line hemofiltration (HF). Fourteen chronic hemodialysis patients (9 males mean age 72.21±11.21 years old) underwent 6 four-hour dialysis sessions for 2 weeks on each of the 4 studied techniques.

Results

The AFBK technique presented less intradialytic hypotensive episodes (1 in 84 sessions) compared to the other techniques (HD: 29/84, HDF 22/82 and HF: 14/78; P<0.001). The blood pressure after one, two, three hours of dialysis and at the end of the hemodialysis session was significantly higher in the AFBK technique. On AFBK the net ultrafiltration (UF) (P<0.001) and the UF as a percentage of the dry weight (P=0.005) were significantly higher. A significant correlation between the prevalence of hypotensive episodes and the change of serum potassium levels (P=0.002) during the first hour of dialysis was detected.

Conclusions

AFBK is associated with a better intradialytic hemodynamic tolerance and could be an optimal method for frail hypotension-prone hemodialysis patients.

En immunoanalyse, certains tests utilisent des anticorps ou des antigènes biotinylés couplés à des microparticules tapissées de streptavidine. Dans certaines circonstances, une supplémentation en biotine peut être à l’origine de résultats erronés. Dans cet article, nous rapportons deux cas cliniques avec des résultats de thyréostimuline (TSH) et parathormone (PTH) artefactuellement abaissés, et de thyroxine libre (T4L) artefactuellement élevés liés à la prise de biotine per os dans un contexte clinique d’insuffisance rénale chronique. Devant ces interférences franches, nous avons réalisé un travail de surcharge in vitro de sérums en biotine afin d’évaluer l’interférence en fonction de la concentration en biotine. En prenant la place de l’anticorps ou de l’antigène biotinylé au niveau de la streptavidine, la biotine peut provoquer une baisse du signal qui apparaît comme une diminution de la concentration de l’analyte pour une méthode sandwich (cas de la TSH et de la PTH) ou comme une augmentation de l’analyte à doser pour une méthode par compétition (cas de la thyroxine libre). En conclusion, un défaut d’élimination de biotine, du fait de l’insuffisance rénale, est, pour plusieurs méthodes de dosage, un facteur facilitant l’obtention et la persistance d’une concentration sérique interférente de biotine sur plus de 48 heures après arrêt de la supplémentation.

In clinical chemistry, many immunoassays apply biotin and streptavidin in the assay principle. Presence of high levels of biotin in patient samples can produce negative or positive interference depending on the assay format. In this study, we describe 2 clinical cases with chronic kidney failure and with unusual thyroid and parathyroid function test results due to biotin interference. We studied the impact of biotin levels on thyroid stimulating hormone (TSH), free thyroxine (T4L) and parathormone (PTH) results with a pool of sera loaded with several concentrations of biotin. In sandwich assays (TSH and PTH), excess biotin displaces biotinylated antibodies resulting in apparently low concentration of the analyte. With competitive immunoassays (T4L), excess biotin competes with biotinylated analog for the binding sites on streptavidin resulting in low signal and falsely high concentration of the analyte. In conclusion, chronic kidney failure combined to therapeutic biotin is in favour of high levels of biotin which causes seriously misleading results in assays using biotin-streptavidin mechanisms.