Aim of the study. - To evaluate the reactivity of the new Elecsys (R) protactin II (PRLII) immunoassay with macroprolactin.Material and methods. - We compared the results of the two Elecsys (R) prolactin assays from Roche Diagnostics, the old protactin (PRL) and the new protactin II in 213 hyperprotactinernic sera as measured with the PRL assay. Macroprolactin was determined after polyethylene glycol (PEG) precipitation using the PRL assay (MPRL). One hundred and two sera were considered as macroprolactin negative (MPRL < 50%), 87 positive (MPRL >= 60%) and 24 undetermined. Monomeric prolactin was measured with the PRL assay (PRLm) in all samples and with the PRLII assay (PRLIIm) in 142 from the 144 samples with increased PRLII values.Results. - In the negative group, PRL and PRLII results were perfectly correlated (r = 0.998) but PRLII values were 20-30% lower than PRL values. In the positive group, macroprolactin was detected to a lesser extent by the PRLII assay than by the PRL assay (49 sera with increased PRL results had PRLII results within the reference interval) but the PRLII assay was still reactive with macroprolactin (among 82 sera with PRLm within the reference interval 33 had increased PRLII results). Correlation (r = 0.98 and concordance (95%) between PRLm and PRLIIm values determined in 142 sera were good.Conclusion. - The prolactin II assay reacts less strongly than the prolactin assay with macroprolactin. However, the PEG precipitation and monomeric protactin determination are still required to confirm hyperprolactinemia. (C) 2008 Elsevier Masson SAS. Tous droits reserves.

AIM:Glargine, a long-acting insulin analogue, is metabolized in the bloodstream and in subcutaneous tissue. Glargine metabolism and its implications for diabetes therapy remain poorly understood. The aim of our study was to assess in vitro the glargine blood biotransformation and its inter-individual variability. METHODS:Formation of M1 glargine metabolite in vitro was studied with Elecsys Insulin immunoassay in pools of sera and sera from patients spiked with glargine. Elecsys Insulin assay is specific of human insulin, does not recognize glargine and its M2 metabolite but does recognize its M1 metabolite. RESULTS:Glargine incubation with serum resulted in M1 metabolite formation which was detected and characterized as an enzymatic process: metabolite kinetics were dependant on temperature, substrate concentration and serum proportion. Carboxypeptidase inhibitors and chelating agents partially inhibited the activity of the enzyme(s). Glargine biotransformation was decreased when blood was collected on EDTA tubes. After 30 min incubation of glargine (100 mU/l) in 69 sera at 37 degrees C, percentage of glargine converted into M1 ranged from 46% to 98% (mean 72%; S.D. 11%). CONCLUSION:Glargine blood biotransformation is an enzymatic process probably involving serum carboxypeptidase(s). Metabolite formation is rapid and non negligible. Inter-individual variability of glargine biotransformation is noteworthy and should be confronted to M1 metabolite bioactivity which has not been fully documented yet.

Aim of the study. - To evaluate the specificity of a direct urinary free cortisol assay. Material and methods. - We studied 27 urinary samples from the Probioqual external quality assessment program. We compared the results obtained in our laboratory using a direct RIA (Immunotech IM1841) with those determined by Probioqual using the reference method, gas chromatography-mass spectrometry (GC-MS).Results. - Correlation between the results of the two methods was good (r = 0.978) and the regression line was the following: RIA (nmol/L) = 1.10 GC-MS (nmol/L) - 3.4. All relative differences but one lay between -20 and +30% and no clear discordance was observed. Conclusion. - This study on quality control material confirms the good specificity of the direct RIA previously observed on clinical samples from untreated and corticoid treated patients. (C) 2007 Elsevier Masson SAS. Tous droits reserves.

Following the introduction of a new formulation of the Elecsys free triiodothyronine (fT3) assay from Roche Diagnostics (Meylan, France) in our laboratory in November 2003, we experienced an increased frequency of high fT3 results not associated with low thyrotropin (TSH) values (1). The Elecsys fT3 assay is a competitive immunoassay involving a specific anti-T3 sheep monoclonal antibody labeled with a ruthenium complex, T3-biotin, and streptavidin-coated microparticles. The occurrence of a high fT3 result without a low TSH level is rare. Apart from the statistical 2.5% of euthyroid patient results found slightly above the upper fT3 limit, this association can be found in sera from patients treated with T3 or triiodothyroacetic acid (2, 3) (these treatments are not frequently used in our patients) or in sera containing an interfering substance: heterophilic antibodies, anti-T3 antibodies (4), anti-ruthenium antibodies (involved in the Elecsys assay) or interfering drugs such as non-steroidal antiinflammatory drugs (5). We report here the results obtained for 15 sera collected between May 2004 and March 2006. In these samples, high Elecsys fT3 results could not be confirmed with the Ria-gnost fT3 radioimmunoassay from CIS biointernational (Gyf-surYvette, France). Run in a two-step format, this assay is free from anti-T3 antibody interference (4). Riagnost fT3 results were within the reference interval (Table 1). The procedures were in accordance with the Helsinki Declaration of 1975 and the subsequent 1996 amendments. No drug known to possibly interfere in fT3 assays identified from clinical notes, interference from hete-

L'interférence des anticorps hétérophiles, généralement détectée par le clinicien confronté à des données cliniques et biologiques discordantes, est un problème encore mal résolu pour les immunodosages. Au laboratoire, nous avons recherché une interférence dans un dosage de triidothyronine libre (T3L) en analysant la cohérence du résultat de T3L Elecsys avec celui de TSH Elecsys. Sur 10 000 couples étudiés entre mai 2004 et octobre 2005, la T3L est apparue élevée 38 fois sans abaissement de la TSH. L'élévation de la T3L n'a été confirmée avec le dosage radioimmunologique en deux étapes Ria-gnost que dans 14 de ces sérums. 24 sérums sont donc suspects d'interférence. Les recherches d'anticorps anti-T3, anticorps hétérophiles et d'interférences médicamenteuses entreprises au laboratoire n'ont pas donné d'explication à ces discordances. En revanche, sur 16 de ces 24 sérums discordants qui ont pu être étudiés complètement par le fabricant, une interférence d'anticorps anti-idiotype a été mise en évidence dans trois cas et d'anticorps anti-ruthénium dans les 13 autres cas. Le fabricant a développé un réactif qui à l'avenir devrait neutraliser l'interférence des anticorps anti-ruthénium. L'interférence des anticorps anti-idiotype reste plus difficile à maîtriser. Sa fréquence de l'ordre de 0,03 % dans cette étude, est compatible avec l'état de l'art des immunodosages actuels : moins de 0,05 % de cas d'interférence d'anticorps hétérophiles.

L’objectif de cette étude est de comparer les propriétés pharmacodynamiques des deux modalités d’administration de l’insuline basale au cours d’une épreuve de jeûne total de 36 heures pratiquée par 24 diabétiques de type 1 lors de leur formation à l’insulinothérapie fonctionnelle. Au cours de l’étude, seule l’insuline basale a été délivrée et la dose a été déterminée individuellement par la formule d’Howorka.Quinze patients étaient traités par une injection quotidienne d’un analogue lent (groupe Glargine) et neuf par perfusion continue à débit unique par pompe d’un analogue rapide (groupe Pompe). En cas d’hyper- ou d’hypoglycémie, une correction insulinique ou une collation glucidique ont été respectivement délivrées afin de maintenir une glycémie normale (0,6-1,2 g/l).L’analyse des courbes de mesure en continu du glucose interstitiel (Glucoday®) a permis de déterminer les paramètres de variabilité glycémique asymptomatique suivants : écart type de la moyenne des concentrations de glucose interstitiel, index MAGE (Mean Amplitude Glycemic Excursions) et MODD (Mean Of Daily blood glucose Differences).Les résultats montrent que la moyenne et l’écart-type de la moyenne des concentrations de glucose interstitiel, les index MAGE et MODD ne diffèrent pas significativement entre les deux groupes. Le nombre de collations glucidiques administrées est identique dans les deux groupes, mais le nombre de corrections insuliniques administrées est plus élevé dans le groupe pompe.En conclusion, le contrôle glycémique au cours d’un jeûne total de 36 heures est au moins aussi satisfaisant avec une injection quotidienne d’un analogue lent de l’insuline (glargine) qu’avec la perfusion continue à débit unique par pompe d’un analogue rapide de l’insuline (lispro ou asparte).The aim of the study was to compare the pharmacodynamics properties of the two modes of basal insulin administration during a 36 hours total fast in 24 type 1 diabetics training for functional insulin therapy. During the course of the study only basal insulin was delivered and dose was determined for each patient using the Howorka formula.Fifteen patients were treated with daily long acting analogue insulin injection (Glargine group) and 9 with continuous subcutaneous insulin infusion (CSII) of a fast acting analogue at a constant basal infusion rate (CSII group). In case of hyper- or hypoglycemia, insulin correction or carbohydrate collation were respectively provided in order to recover normoglycemia (60 - 120 mg/dL).The analysis of the interstitial glucose curves (Glucoday®) has allowed to determine the following asymptomatic glycemic variability indexes: standard deviation of mean interstitial glucose concentration, MAGE (Mean Amplitude Glycemic Excursions) and MODD (Mean Of Daily blood glucose Differences).Results showed that mean interstitial glucose level and standard deviation of the mean interstitial glucose level, MAGE and MODD index were not significantly different between the two groups. The number of « carbohydrate intake » provided was similar in the two groups but the number of insulin corrections provided was higher in the CSII group.In conclusion, maintenance of glycemic stability during a 36 hours total fast is at least as effective with long acting insulin injection (glargine) as it is with CSII at a constant basal infusion rate (lispro or aspart).

Les interférences sont très nombreuses dans les méthodes d’immuno-analyse; elles sont source d’erreurs par défaut ou par excès parfois au détriment de la qualité des soins au patient, en particulier concernant les hormones, les marqueurs cardiaques et les marqueurs tumoraux. La réaction croisée résulte d’un défaut de spécificité des anticorps (AC) de la trousse et de la présence de cross-réactants; elle concerne surtout des dosages hormonaux dans des situations bien connues. La principale cause d’interférence reste la présence d’anticorps dans le sérum du patient, essentiellement des auto-AC et des AC hétérophiles; il est important de les mettre en évidence et de lever l’interférence. Les nouvelles trousses seraient moins sensibles à ce type d’interférences. L’interférence par excès d’antigène doit être anticipée par des tests de dilution et l’adaptation des méthodes. Il existe d’autres types d’interférences, comme par des protéines endogènes (albumine, protéines de transport, complément immunologique) et bien sûr l’effet matrice, ou la présence de biotine dans l’échantillon. Malgré les progrès réalisés en immuno-analyse, il restera toujours des causes d’interférence et il peut en apparaÎtre de nouvelles. Le biologiste doit rester vigilant et formé sur ces méthodes d’analyse et les principales causes d’interférence.Interferences are frequent in immuno-assays; they are the cause of errors with default or excess, sometimes to the detriment of the quality of medical care, in particular for hormones, cardiac markers and tumor markers. Cross-reaction can come from a low specificity of the antibodies and from the presence of cross-reacting products, mostly for hormone assays in well-known situations. The main cause of interference remains the presence of antibodies in patient serum, such as auto-antibodies and heterophilic antibodies. It is particularly important to detect them and to remove the interference. New kits should be less sensitive to this type of interference. The interference with antigen excess or “hook effect” must be anticipated with dilution testing and the adaptation of the methods. Other types of interferences or pitfalls concern endogen proteins, such as specific binding-proteins, albumin, or immunological complement, also matrix effect or the presence of biotin in the sample. In spite of recent progress in immuno-assays, it will always remain some causes for interference and some others can appear. The biologist has to be vigilant and trained on these methods of analysis and on the main causes for interfering.

Parmi les méthodes envisagées pour mettre en évidence la macroprolactine dans le sérum, la comparaison des résultats d'une méthode reconnaissant fortement la macroprolactine telle que l'Elecsys à ceux d'une méthode la reconnaissant faiblement pourrait être une alternative pratique. Malheureusement, cette méthode a donné jusqu'alors des résultats décevants. La mise à disposition du dosage Kryptor ayant une reconnaissance de la macroprolactine plus faible que celle des immunodosages testés précédemment, nous a incités à entreprendre une étude comparative des résultats de prolactine Elecsys et Kryptor. Cette étude a été conduite sur un grand nombre d'échantillons : 149 sérums négatifs en macroprolactine d'après le test au PEG Elecsys (% de précipitation <40) et 149 sérums positifs (% de précipitation ≥60). Les résultats confirment la moindre sensibilité à la macroprolactine du dosage Kryptor par rapport à l'Elecsys. Cependant, bien que l'étude n'ait porté que sur des sérums franchement négatifs ou positifs d'après le test au PEG, l'analyse des différences relatives entre les résultats des deux dosages, (Elecsys-Kryptor)/Elecsys, fait apparaître un chevauchement important entre les résultats des groupes négatif et positif. Ces observations s'expliquent probablement par la grande hétérogénéité des formes circulantes de prolactine et de macroprolactine. Ces différentes formes sont reconnues d'une façon différente par les immunodosages.

In connection with a comparative study of nine kits for the measurement of free thyroxin, we determined reference values in a adult control group of 81 women and 73 men. The correlations observed between the kits are associated with very large differences in the results obtained. The reference ranges are more or less broad according to the kits, but narrower than those offered by the manufacturers.

Serum thyrotropin (TSH) measurements are widely used in the diagnosis of thyroid dysfunction and to monitor l-thyroxine (T4) replacement therapy in primary hypothyroidism. The accepted TSH reference interval in serum is 0.4–4.0 mIU/L, and a TSH concentration between 0.5 and 2.0 mIU/L is generally considered as the optimum therapeutic target during replacement therapy (1). Because of technical problems such as interference from heterophilic antibodies reacting with assay anti-mouse antibodies, immunometric assays may give falsely increased TSH values (1). Chimeric antibodies have been introduced in some assays with a view to eliminate interference from anti-mouse antibodies (2). We report here for the first time two cases of misleading high TSH results obtained with an immunometric assay involving a chimeric anti-TSH antibody. The first case (patient 1), a 56-year-old woman on long-term l-T4 replacement therapy, was referred to the laboratory for biological thyroid follow-up. Her serum TSH concentration had been slightly above the reference interval for 2 years. The TSH value (5.4 mIU/L) measured with the Elecsys immunometric assay performed on the Elecsys 2010 analyzer (Roche Diagnostics) confirmed this finding. This slightly increased TSH value was in agreement with the previous TSH results but disagreed with the free thyroxine (FT4) concentration (20.5 pmol/L) measured on the Elecsys platform, which was within the reference interval (12.2–23.2 pmol/L). As expected, in the serum from this adequately treated patient who was clinically euthyroid, FT4 was in the upper third of the reference interval (1), but surprisingly, TSH remained slightly increased. This unexpected TSH value prompted further TSH measurements with two other methods. The results were 0.51 mIU/L with the ADVIA Centaur TSH-3 assay (Bayer Diagnostics) and 0.27 mIU/L with the Architect TSH assay (Abbott Diagnostics Division). In the one-step Elecsys assay, the first antibody, a mouse biotinylated monoclonal anti-TSH …

La macroprolactine ou big-big prolactine constituée essentiellement de complexes prolactine-IgG inactifs in vivo est reconnue par les immunodosages actuels. Elle est une cause fréquente d’hyperprolactinémie. La précipitation au polyéthylène glycol (PEG) permet d’éliminer la macroprolactine mais peut s’accompagner d’une précipitation significative de prolactine monomérique et de big prolactine. Pour la prolactine monomérique dosée dans le surnageant de précipitation au PEG, un seuil d’hyperprolactinémie doit donc être déterminé. La prolactine a été dosée par méthode Elecsys avant et après précipitation au PEG 25 %, volume à volume, dans 284 sérums sans hyperprolactinémie (prolactine < 600 mUI/L) et sans macroprolactine (prolactine précipitée < 40 %). La prolactine monomérique a été calculée à partir de la prolactine mesurée dans le surnageant multipliée par 2. De plus, ont été étudiés les résultats de prolactine monomérique de 178 sérums avec hyperprolactinémie (prolactine > 600 mUI/L) et macroprolactinémie (prolactine précipitée > 60 %). Le seuil d’hyperprolactinémie monomérique établi à partir des 284 sérums témoins est de 475 mUI/L. Seize pour cent des 178 sérums hyperprolactinémiques et macroprolactinémiques ont une concentration de prolactine monomérique supérieure à ce seuil. En conclusion, la macroprolactine n’est pas toujours la seule cause de l’hyperprolactinémie et la prolactine monomérique doit donc être estimée afin d’éviter des erreurs diagnostiques. Macroprolactin or big-big prolactin, is a high molecular weight prolactin-IgG complex which is, at least partly, measured by commercial immunoassays and can cause hyperprolactinemia. Polyethylene glycol (PEG) precipitation eliminates macroprolactin from serum but can also partly precipitate monomeric prolactin and big prolactin. Regarding monomeric prolactin measurements in the PEG supernatant, a specific threshold of hyperprolactinemia has to be determined. We measured prolactin with the Elecsys assay before and after, volume by volume, 25% PEG precipitation in 284 sera without hyperprolactinemia (prolactin <600 mIU/L) and without macroprolactinemia (PEG precipitation <40%). Monomeric prolactin was estimated by multiplying the prolactin measured in the PEG supernatant by 2. We also studied 178 hyperprolactinemic sera with macroprolactin (PEG precipitation >60%). The hyperprolactinemia threshold obtained from the 284 control sera was 475 mIU/L. Out of the 178 hyperprolactinemic sera, 16% had monomeric prolactin concentrations over this threshold. In conclusion, macroprolactin is not always the sole cause of hyperprolactinemia and monomeric prolactin should be estimated to avoid misdiagnosis.

Le dosage de la prolactine, de réalisation sans doute trop systématique dans le cadre du bilan d’infertilité, pose bien souvent des problèmes d’interprétation et de stratégie diagnostique. L’élévation plasmatique de la prolactine est de constatation fréquente puisque notée dans 20 à 30 % des troubles du cycle et chez 10 % des femmes normalement réglées. Néanmoins, toute hyperprolactinémie ne doit pas faire systématiquement l’objet d’un bilan paraclinique exhaustif même s’il est parfois difficile de faire la part la part des choses entre hyperprolactinémie « organique », fonctionnelle voire artéfactuelle. Il importe donc avant tout d’affirmer la réalité de l’hyperprolactinémie avec une méthode de dosage rigoureuse, puis ensuite d’utiliser à bon escient les tests dynamiques et l’imagerie de la région hypothalamo-hypophysaire, de façon à évoluer dans l’arbre diagnostique souvent complexe des étiologies d’excès de prolactine.Serum prolactin measurement is usually performed in infertility evaluation, even if there’s no specific clinical presentation of hyperprolactinemia. High levels of prolactin are noted in 20 to 30% of menstrual abnormalities and in about 10% of regular menses. It is of importance to determine whether hyperprolactinemia is related to pituitary adenoma, drug administration, general diseases, or circulating large forms of prolactin, in order to avoid heavy, expensive, time consuming and unnecessary clinical investigations or therapeutic actions. We must first to confirm the biological diagnosis of hyperprolactinemia with few repeated plasmatic measurements, and, later, if necessary use TRH-metoclopramide test and/orpituitary magnetic resonance imaging.

Nous avons réalisé une étude analytique du dosage de testostérone VIDAS, technique Elfa (Enzyme Linked Fluorescent Assay) et comparé les résultats à ceux de 2 techniques : l’une automatique, électrochimiluminescence Elecsys et l’autre manuelle, RIA Immunotech. La répétabilité et la reproductibilité du VIDAS sont satisfaisantes. La limite de détection analytique a été trouvée à 0,025 ng ml–1. Les résultats de 6 sérums obtenus par le dosage VIDAS et la spectrométrie de masse (ID-GCMS) sont très bien corrélés. Deux cent dix sérums, dont 40 témoins, adressés au laboratoire pour un dosage de testostérone, ont été dosés par les 3 méthodes. La trousse VIDAS donne des résultats bien corrélés avec ceux de la technique Elecsys, la corrélation est moins bonne avec Immunotech. Les diagrammes des différences font apparaître des écarts inter-techniques importants pour certains échantillons. Chez les témoins, hommes et femmes, les valeurs de référence données par le fabricant ont été confirmées. Chez 7 femmes avec un diagnostic clinique d’hirsutisme, comme attendu, une élévation de la concentration de testostérone a été observée avec le VIDAS et les 2 autres trousses. L’interprétation des résultats des sérums de femmes reste délicate en particulier en cas de traitement, quelle que soit la trousse étudiée.

OBJECTIVE:To assess the antigenicity of the insulin Hoechst 21PH (Hoe21PH) using continuous subcutaneous insulin infusion (CSII) and to compare the antigenicity of this insulin when administered intraperitoneally or subcutaneously. RESEARCH DESIGN AND METHODS; Peritoneal administration of Hoe21PH (Hoechst-Roussel, Somerville, NJ) insulin using implantable devices (continuous peritoneal insulin infusion [CPII]) increases anti-insulin antibody (AIA) levels in type 1 diabetic patients. Intraperitoneal administration, addition of a stabilizer (polyethylene polypropylene glycol), or insulin modifications due to storage in the pump may be involved in this antigenicity. In this nonrandomized study, 24 type 1 diabetic patients were treated with either CSII (n = 11, group 1) or CPII (n = 13, group 2). AIA levels were measured by radioimmunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA) before starting patients on Hoe21PH and again after 3 and 6 months.RESULTS:Patients were comparable in the two groups. AIA levels (RIA) remained stable (24.3 +/- 8.5% [month 0] to 24.9 +/- 8.5.5% [month 6]) in group 1 and increased (21.8 +/- 6.7% [month 0] to 41.8 +/- 6.9% [month 6]) in group 2 (P = 0.005, Wilcoxon's rank-sum test). Using ELISA, AIA remained stable in the patients in group 1 (n = 9; 3.8 +/- 0.8 units/ml [month 0] and 4.1 +/- 1.0 units/ml [month 6]) and tended to increase in the patients in group 2 (n = 12; 4.1 +/- 0.7 units/ml [month 0] to 17.5 +/- 4.6 units/ml [month 6]) (P = 0.07). Comparison of the evolution of AIA formation between the two groups, using RIA at months 0, 3, and 6 showed a significant difference (analysis of variance, P = 0.009).CONCLUSIONS:No increase in AIA levels was demonstrated when Hoe21PH insulin was administered subcutaneously as assessed by two different assays. CPII is proven to be more antigenic than CSII, and this is not related to a specific antigenicity of Hoe21PH insulin. The intraperitoneal route of administration or insulin modifications due to insulin storage in implantable devices might explain this antigenicity.

Background: The Elecsys(R), prolactin (PRL) assay reacts more strongly with macroprolactin than the Centaur(R) PRL assay. We evaluated Elecsys direct and free PRL measurements vs. Centaur direct PRL measurements, in sera with and without macroprolactin. Methods: PRL was measured using Elecsys and Centaur direct assays and the Elecsys assay in the supernatant obtained after PEG precipitation (free PRL) in 34 sera from 34 hyperprolactinemic male subjects (Elecsys direct PRL > 434 mIU/l) classified, according to the PRL recovery after PEG precipitation, as: negative, i.e. without predominant macroprolactin (recovery %>50, n = 12), positive (recovery % < 40, n = 18) or indeterminate (n = 4). Results: The positive bias between Elecsys direct and Centaur PRL results was clearly influenced by the presence of macroprolactin and the mean bias between Elecsys free and Centaur prolactin values was near zero in the negative and positive groups. Among 14 patients from the positive group presenting clinical conditions possibly ascribable to hyperprolactinemia, Elecsys free and Centaur PRL levels were normal in seven and increased in five. In the negative and positive groups considered together, Elecsys free PRL agreed well with Centaur prolactin (28/30). The poor concordance observed for the indeterminate samples underlined the heterogeneity of macroprolactin. Conclusion: Elecsys free PRL determination can be used to reduce the marked influence of macroprolactin in this assay. (C) 2002 Elsevier Science B.V. All rights reserved.

Le but de notre travail a été d'évaluer le nouveau dosage d'anticorps anti-thyroglobuline (anti-Tg) sur automate Elecsys et de comparer les résultats à ceux de la trousse RIA BRAHMS. Le dosage Elecsys est pratique et reproductible. Le seuil de positivité à 115 UI/l a été confirmé avec une positivité de 7 % chez 99 témoins (8 % avec BRAHMS). Avec une spécificité comparable, le dosage Elecsys a présenté une sensibilité supérieure à celle du RIA BRAHMS pour le diagnostic d'une pathologie thyroïdienne auto-immune chez les patients atteints de maladie de Hashimoto (73 % vs 59 %, n = 46) ou de Basedow (39 % vs 31 %, n = 76). Il en a été de même chez 13 autres patients dont les résultats étaient discordants, Elecsys positif / BRAHMS négatif. Les valeurs numériques des deux dosages sont très différentes. Cela souligne une nouvelle fois la difficulté de standardisation du dosage des anti-Tg.

Insulin assays are used in the identification of rare hypoglycemic syndromes, and may be useful in classifying the different types of diabetes (1)(2)(3). Hemolysis (4)(5)(6) and circulating anti-insulin antibodies (7)(8) are sources of interference in insulin determinations. Anti-insulin antibodies may be present in the serum of insulin-treated diabetic patients, even when they are treated with biosynthetic human insulin, and may also be found in the serum of type 1 diabetic patients before insulin administration. These antibodies interfere in competitive and noncompetitive insulin immunoassays. In the increasingly used two-site noncompetitive assays, anti-insulin antibodies may yield increased results. Thus, anti-insulin antibodies must be eliminated, usually through precipitation with polyethylene glycol, before the concentration of free (active) insulin is determined (9). In addition to these considerations, both biosynthetic human insulin and insulin lispro, a fully potent analog with a faster absorption rate, are used therapeutically so that not only human endogenous and exogenous insulin, but also insulin lispro may be present in samples in which the insulin assay is to be used. In the present study we performed a preliminary evaluation of an insulin electrochemiluminescence immunoassay recently developed by Roche Diagnostics (Mannheim, Germany) for the Elecsys® analyzer. We studied the analytical performance of this new insulin assay and assessed the results of insulin measurements in serum samples with and without anti-insulin antibodies. The Elecsys assay uses an 18-min incubation time and a 20-μL sample volume, and has a stated dynamic range of 0.2–1000 mIU/L (1.39–6945 pmol/L). Assays were performed on the Elecsys 2010 analyzer in singleton, according to the manufacturer’s instructions, with two different lot numbers. The Elecsys results were compared with those of our routine method (Bi-Insulin IRMA; Bio-Rad) in EDTA-plasma samples from 110 diabetic patients treated with oral hypoglycemic drugs …

Numerous methods are proposed to quantify antithyroid peroxidase autoantibodies. No standardization exists but most assays use the standard MRC 66/387 with a calibration factor. Costs of the tests vary between the different kits. We evaluated the concordance of eight peroxidase autoantibodies assay kits in two centres, using a panel of sera from 269 subjects: controls (n=100), patients with autoimmune thyroid disease (n=77; Graves' disease, Hashimoto's thyroiditis), patients with non-autoimmune thyroid disease (n=69; nodular goiter, differentiated thyroid carcinoma) and individual sera with thyroglobulin antibodies only (n=23). The concordance between the eight methods was high, ranging from 88.3% to 98.8% with the total panel of sera. The majority of assays demonstrated high diagnostic performance. We encountered some false-positive results at borderline positive levels, and the nonrecognition of some sera by competitive assays.