Insuffisance rénale chronique et biotine : un duo propice aux bilans thyroïdiens et parathyroïdiens erronés, à propos de 2 cas

Free thyroid hormone: Methods and standardization

Free thyroid hormone (FTH) serves as the preferred indicator for the clinical assessment of thyroid function, mainly encompassing free thyroxine and free triiodothyronine. The immunoassay commonly employed in the clinical setting exhibits certain unresolvable deficiencies. The results of over 5,500 clinical laboratories for FTH from China in 2024 demonstrated that the outcomes of immunoassay were not comparable, with robust CVs calculated in accordance with ISO 13528 ranging from 13.82% to 21.42%. Establishing reference methods is an important tool to achieve accurate and comparable results of free hormones. Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) holds a distinct advantage in the precise detection of small molecules, and two reference methods for free thyroxine based on LC-MS/MS are included in the JCTLM list. This article conducts a comprehensive review of the detection methods and standardization of FTH. It presents the metabolism of thyroid hormones, the significance of detection, the techniques, and application examples of free thyroid hormone assays, and deliberates on the current status, prospects, and recommendations for the standardization of FTH assays. Immunoassay and LC-MS/MS, as significant techniques for FTH detection, are predominantly emphasized in the case references. Ultrafiltration and equilibrium dialysis, which are utilized to separate FTH, are also addressed. This article aims to discuss the status quo of FTH detection and clarify the advantages of LC-MS/MS in FTH detection, propose that LC-MS/MS can be utilized as an auxiliary validation method or alternative method in clinical applications, and offer suggestions for the standardization of testing results.

Vitamin Needs and Treatment for Chronic Kidney Disease Patients

This paper summarizes the biochemistry, metabolism, and dietary needs of vitamins in patients with chronic kidney disease (CKD) and kidney transplant recipients. Evidence indicates that the dietary intake, in vivo synthesis, urinary excretion or metabolism of different vitamins may be substantially altered in kidney failure. There are discrepancies in vitamin status assessment depending on whether the assay is functional or measuring the blood vitamin level. Whether vitamin supplements should be routinely prescribed for patients with CKD is controversial. Because low dietary intake and compounds that interfere with vitamin activity are not uncommon in patients with CKD, and water-soluble vitamin supplements appear safe and not costly, the authors recommend that supplements of the water-soluble vitamins should be routinely offered to these individuals. More research is needed to assess vitamin nutrition and function and to determine the daily vitamin needs for all patients with CKD.

Hormone Immunoassay Interference: A 2021 Update

Immunoassays are powerful qualitative and quantitative analytical techniques. Since the first description of an immunoassay method in 1959, advances have been made in assay designs and analytical characteristics, opening the door for their widespread implementation in clinical laboratories. Clinical endocrinology is closely linked to laboratory medicine because hormone quantification is important for the diagnosis, treatment, and prognosis of endocrine disorders. Several interferences in immunoassays have been identified through the years; although some are no longer encountered in daily practice, cross-reaction, heterophile antibodies, biotin, and anti-analyte antibodies still cause problems. Newer interferences are also emerging with the development of new therapies. The interfering substance may be exogenous (e.g., a drug or substance absorbed by the patient) or endogenous (e.g., antibodies produced by the patient), and the bias caused by interference can be positive or negative. The consequences of interference can be deleterious when clinicians consider erroneous results to establish a diagnosis, leading to unnecessary explorations or inappropriate treatments. Clinical laboratories and manufacturers continue to investigate methods for the detection, elimination, and prevention of interferences. However, no system is completely devoid of such incidents. In this review, we focus on the analytical interferences encountered in daily practice and possible solutions for their detection or elimination.

Biotin interference: evaluation of a new generation of electrochemiluminescent immunoassays for high-sensitive troponin T and thyroid-stimulating hormone testing

Background

Biotin is currently a matter of concern for laboratories using biotin-streptavidin-based immunoassays. Biotin interferences have been reported for high-sensitive troponin T (hsTnT) and thyroid-stimulating hormone (TSH) assays. We aimed to evaluate the new generation of hsTnT and TSH electrochemiluminescent immunoassays announced to be less sensitive to biotin.

Methods

Firstly, we assessed the analytical performances of new generation assays (imprecision, bias, total error, limit of quantification) and compared previous and new generation assays in the absence of biotin. Secondly, we challenged both generations of assays with samples spiked with seven different biotin levels. The efficiency of new generation assays was also compared to the streptavidin beads treatment.

Results

New generation assays presented suitable analytical performances. Previous and new generations of hsTnT and TSH assays were commutable in the absence of biotin. In the presence of biotin, we confirmed that previous generation assays were affected by biotin concentration as low as 40.5 ng/mL and that new generation assays were not affected up to the announced tolerance threshold of 1200 ng/mL. After the streptavidin beads treatment, we observed a higher imprecision for both parameters and a constant 10% negative bias for TSH compared to new generation assays.

Conclusions

New generation of electrochemiluminescent immunoassays appears as a reliable systematic solution to prevent biotin interference for hsTnT and TSH testing.

Interferences With Thyroid Function Immunoassays: Clinical Implications and Detection Algorithm

Automated immunoassays used to evaluate thyroid function are vulnerable to different types of interference that can affect clinical decisions. This review provides a detailed overview of the six main types of interference known to affect measurements of thyroid stimulating hormone (TSH), free thyroxine (T4) and free triiodothyronine (T3): macro-TSH, biotin, antistreptavidin antibodies, anti-ruthenium antibodies, thyroid hormone autoantibodies, and heterophilic antibodies. Because the prevalence of some of these conditions has been reported to approach 1% and the frequency of testing for thyroid dysfunction is important, the scale of the problem might be tremendous. Potential interferences in thyroid function testing should always be suspected whenever clinical or biochemical discrepancies arise. Their identification usually relies on additional laboratory tests, including assay method comparison, dilution procedures, blocking reagents studies, and polyethylene glycol precipitation. Based on the pattern of thyroid function test alterations, to screen for the six aforementioned types of interference, we propose a detection algorithm, which should facilitate their identification in clinical practice. The review also evaluates the clinical impact of thyroid interference on immunoassays. On review of reported data from more than 150 patients, we found that ≥50% of documented thyroid interferences led to misdiagnosis and/or inappropriate management, including prescription of an unnecessary treatment (with adverse effects in some situations), inappropriate suppression or modification of an ongoing treatment, or use of unnecessary complementary tests such as an I123 thyroid scan. Strong interaction between the clinician and the laboratory is necessary to avoid such pitfalls.

Prevalence of biotin supplement usage in outpatients and plasma biotin concentrations in patients presenting to the emergency department

BACKGROUND

Several cases of biotin interference with laboratory testing have been reported in the literature. However, there are no publications discussing the extent of biotin use or plasma concentrations observed among the patient population. The objective of this study was to determine the prevalence of biotin consumption using two distinct methods: surveying the outpatient population using a questionnaire and quantifying biotin in plasma samples collected from patients presenting to the Emergency Department (ED).

METHODS

Survey questionnaires (n = 4000) were distributed to Mayo Clinic outpatients over one week (July 10-14, 2017). Biotin was quantified in residual waste plasma samples collected for physician-ordered electrolyte panels from patients presenting to the ED (March 6-12, 2017 and March 26-April 4, 2017, n = 1442 unique patient samples).

RESULTS

1944 patients (972 female, 963 male, 9 no answer) with a median (interquartile range) age of 62 (49-72) years returned completed questionnaires (48.6%). From the completed surveys, 7.7% (95% CI, 6.6-8.9%) indicated biotin use. Quantitation of biotin in plasma samples from ED patients (n = 1442) revealed that 7.4% (95% CI, 6.2-8.9%) had concentrations at or above the lowest known threshold (10 ng/mL) for biotin interference in Roche Diagnostics immunoassay tests.

CONCLUSIONS

According to our survey results, reported use of biotin was common. The range of biotin concentrations in ED patient samples highlights the magnitude of the biotin interference problem and identifies a population at risk for potential harm. These findings should guide laboratorians and clinicians in developing effective strategies to mitigate safety risks and in assessing biotin usage trends within their own patient populations.