Interférences dans les immunodosages : mécanismes et conséquences en endocrinologie

Les médicaments qui interfèrent avec les bilans biologiques : revue de la littérature

BACKGROUND

Biological assessment is an integral part of the diagnostic process that guides therapeutic management decisions. However, these analyses remain subject to interference from endogenous or exogenous factors, which may alter the results.

OBJECTIVE

To provide an up-to-date and comprehensive overview of the most commonly documented types of interference attributable to medications, to ensure reliable interpretation of test results and better management of patients.

DATA SOURCES

This comprehensive systematic review of the literature was carried out in 2018. The bibliographic search was carried out in various online databases, specifically PubMed, ScienceDirect and Google Scholar.

STUDY SELECTION

Only publications in French or English concerning medicinal products for human use were retained. The investigators' examination of drug-related interference with laboratory tests was limited to blood assays (serum or plasma).

DATA EXTRACTION

An Excel spreadsheet was used to analyze the results. A total of 82 articles were selected. The interferences studied affected 47 biological parameters corresponding to various types of assessment: hormonal, hepatic, and renal.

DATA SYNTHESIS

The mechanisms reported in the literature identified were analytical (56.9%), physiological (17.82%), and pharmacological (20.11%). The remainder of the mechanisms (5.17%) were not defined.

CONCLUSIONS

Clinicians should be vigilant in validating and interpreting laboratory test results for patients receiving these types of drugs. Dialogue between clinicians and biological scientists is the best way to avoid unnecessary additional testing, which is often cumbersome and costly.

Is insulin intoxication still the perfect crime? Analysis and interpretation of postmortem insulin: review and perspectives in forensic toxicology

Insulin is an anabolic hormone essential to glucose homeostasis. Insulin therapy, comprising human insulin (HI) or biosynthetic analogs, is critical for the management of type-1 diabetes and many of type-2 diabetes. However, medication error including non-adapted dose and confusion of insulin type, and misuse, such as massive self-administration or with criminal intent, can have lethal consequences. The aim of this paper is to review the state of knowledge of insulin analysis in biological samples and of the interpretation of insulin concentrations in the situation of insulin-related death investigations. Analytic aspects are considered, as quantification can be strongly impacted by methodology. Immunoanalysis, the historical technique, has a prominent role due to its sensitivity and ease of implementation. Recently, liquid chromatography coupled to mass spectrometry has provided indispensable selectivity in forensic contexts, distinguishing HI, analogs, and degradation products. We review the numerous antemortem (dose, associated pathology, injection-to-death interval, etc.) and postmortem parameters (in corpore degradation, in vitro degradation related to hemolysis, etc.) involved in the interpretation of insulin concentration. The interest and limitations of various alternative matrices providing a valuable complement to blood analysis are discussed. Vitreous humor is one of the most interesting, but the low diffusion of insulin in this matrix entails very low concentrations. Injection site analysis is relevant for identifying which type of insulin was administered. Muscle and renal cortex are matrices of particular interest, although additional studies are required. A table containing most case reports of fatal insulin poisoning published, with analytical data, completes this review. A logic diagram is proposed to highlight analytical issues and the main parameters to be considered for the interpretation of blood concentrations. Finally, it remains a challenge to provide reliable biological data and solid interpretation in the context of death related to insulin overdose. However, the progress of analytical tools is making the "perfect crime" ever more difficult to commit.

Immunoassay quantification of human insulin added to ternary parenteral nutrition containers: comparison of two methods

Adding insulin directly into infusion bags seems to be a useful method for controlling hyperglycemia in patients under ternary parenteral nutrition (TPN). Its efficacy is assessed by glycemic monitoring but few data are available on insulin stability in this situation. Among the various methods for quantifying insulin levels in human serum, the immunoassay ones seemed potentially appropriate for a TPN admixture containing high lipid concentrations. We sought to identify and validate which of two immunoassay methods was the better to quantify human insulin and consequently be adapted to studying its stability in a TPN admixture. Two immunoassay methods to quantify recombinant human insulin were assessed in industrial TPN: an immunoradiometric assay (IRMA) and an immunoelectrochemiluminometric assay (IECMA). Validation trials for both methods were based on the accuracy profile method. Interference with immunometric assays due to the high lipidic content of TPN was eliminated through an improved preparation protocol using a bovine serum albumin (BSA) diluted in phosphate buffer saline (PBS). The relative total error of IECMA varied from 1.74 to 4.52% while it varied from -0.32 to 8.37% with IRMA. Only IECMA provided an accuracy profile with a 95% confidence interval of calculated-tolerance limits falling between the chosen acceptance limits (i.e., total error ≤±10%). IECMA combined with a BSA dilution is a simple and semi-automatic method that provides an accurate quantification of human insulin in a TPN admixture without any interference from lipids.

Rapid development of sensitive, high-throughput, quantitative and highly selective mass spectrometric targeted immunoassays for clinically important proteins in human plasma and serum

OBJECTIVES

The aim of this study was to develop high-throughput, quantitative and highly selective mass spectrometric, targeted immunoassays for clinically important proteins in human plasma or serum.

DESIGN AND METHODS

The described method coupled mass spectrometric immunoassay (MSIA), a previously developed technique for immunoenrichment on a monolithic microcolumn activated with an anti-protein antibody and fixed in a pipette tip, to selected reaction monitoring (SRM) detection and accurate quantification of targeted peptides, including clinically relevant sequence or truncated variants.

RESULTS

In this report, we demonstrate the rapid development of MSIA-SRM assays for sixteen different target proteins spanning seven different clinically important areas (including neurological, Alzheimer's, cardiovascular, endocrine function, cancer and other diseases) and ranging in concentration from pg/mL to mg/mL. The reported MSIA-SRM assays demonstrated high sensitivity (within published clinical ranges), precision, robustness and high-throughput as well as specific detection of clinically relevant isoforms for many of the target proteins. Most of the assays were tested with bona-fide clinical samples. In addition, positive correlations, (R2 0.67-0.87, depending on the target peptide), were demonstrated for MSIA-SRM assay data with clinical analyzer measurements of parathyroid hormone (PTH) and insulin growth factor 1 (IGF1) in clinical sample cohorts.

CONCLUSIONS

We have presented a practical and scalable method for rapid development and deployment of MS-based SRM assays for clinically relevant proteins and measured levels of the target analytes in bona fide clinical samples. The method permits the specific quantification of individual protein isoforms and addresses the difficult problem of protein heterogeneity in clinical proteomics applications.

Interpretation of hormone levels in older patients: points for consideration

Blood hormone and tumor marker concentrations are usually determined by immunochemical methods which are based on an unique reaction between antigen and assay capture antibody. Despite the speed and simplicity of assays performance on automatic immunochemistry platforms, the interpretation of final results requires a deep knowledge of method fallibility. General lack of immunoassays standardization, presence of cross-reacting substances in patient's sample, limitation of free hormones measurement due to abnormal analyte binding protein concentrations, assay interferences due to patient's autoantibodies, and heterophilic antibodies, as well as proper interpretation of very low- and very high-sample analyte levels, are the main points discussed in respect to hormones and tumor markers measurement in geriatric population.

New onset of heterophilic antibody interference in prostate-specific antigen measurement occurring during the period of post-prostatectomy prostate-specific antigen monitoring

Laboratories evaluated whether an interference was causing a false-positive PSA for the Immulite 2000 immunoassay after a time course of increasing prostate-specific antigen (PSA) in a post-prostatectomy patient led to salvage therapy, which had no effect on the elevated PSA. Serial dilutions of PSA for the patient sample (6.1 ng/mL; post-prostatectomy reference range: <0.1 ng/mL [undetectable]) were linear ( r > 0.99). However, the PSA measurement was reduced to 0.1 ng/mL after pretreatment of the sample with heterophilic antibody blocking reagent. PSA was undetectable (<0.1 ng/mL) when measured using two alternative immunoassays. These results were consistent with the presence of heterophilic antibody interference for the Immulite 2000 assay. In this case, heterophilic antibody interference with PSA measurement must have originated during the period of post-prostatectomy monitoring, and the apparent progressive increases in PSA may have been due solely to the progressive increase of this heterophilic antibody assay interference. In the absence of clinical correlation, positive PSA monitoring results should always be assessed for heterophilic antibody interference for at least one time point.