[Propositions for the standardized expression of HbA 1c results]. / Propositions pour l'expression standardisée des résultats d'HbA 1c.

The 2007 international consensus about the standardization of HbA(1c) determination and expression of results is progressively implemented in most countries. In France, a common working group of the Société française de biologie clinique (SFBC) and the Société francophone de diabétologie (SFD) has expressed the following recommendations. HbA(1c) results are expressed in percentage of total hemoglobin and in mmol HbA(1c)/mol Hb, but are not converted into estimated average glucose. A table indicating the correspondence between HbA(1c) and estimated average glucose may be given with the results, subject to precautions of interpretation at the individual level.

[Hemoglobin A1C determination and hemoglobinopathies: problems and strategies]. / Dosage de l'hémoglobine A(1c) et hémoglobinopathies: problèmes posés et conduite à tenir.

The semiological value of hemoglobin A1c (HbA1c) as a retrospective and cumulative marker of glycemic balance in diabetic patients is greatly weakened in case of hemoglobinopathy. The presence of an abnormal hemoglobin raises methodological problems due to the interferences generated in most assay methods, but also alters the normal process of HbA glycation to HbA1c, and often induces a certain level of hemolysis, very variable and impossible to quantify. This paper reviews methodological and semiological problems related to the presence of abnormal hemoglobin species, and proposes a standardized strategy in case of hemoglobinopathies.

[Considerations on delocalized HbA1c assays]. / Réflexions sur les dosages délocalisés d'hémoglobine A1C.

Availability and knowledge of HbA(1c) value during consultation is an important feature for diabetologists, that permits a better adaptation of therapy and a better motivation of patients. This expectation explains the request for delocalized assays of HbA(1c), even though life prognosis is not affected, like in the other cases of point of care testing. One of the most frequent solutions is the use of immunological delocalized HbA(1c) assays. Technically, these methods have to meet the same criteria as those used in laboratories. They have to be standardized, and controlled according to the "Guide de Bonne Exécution des Analyses de Biologie Médicale" (GBEA) rules. Solutions chosen for delocalization must respect specific skills of clinicians and biologists and cope with cost limitations. This paper reviews rationales for delocalized HbA(1c) assays, steps of their implementation, and their use in practical routine, with a special emphasis given on the necessary complementarity between clinicians and biologists.

HBA1c: clinical and biological agreement for standardization of assay methods. Report by the experts of ALFEDIAM (Association de Langue Française pour lEtude du Diabète et des Maladies Métabolique) and SFBC (Société Française de Biologie Clinique). / HbA1c: concertation clinico-biologique pour la standardisation des méthodes de dosage. Rapport des experts de l'ALFEDIAM et de la SFBC.

Glycohaemoglobin, and particularly haemoglobin A1c(HbA1c), assays have been used for many years to retrospectively evaluate the glycaemic control of diabetic patients. Cut-off values have been established for deciding treatment modifications. The techniques used in the laboratories however exhibit varying quality, and all of them are not yet standardized. The consequence is an under-utilization of this test, especially in non-hospital practice. In this context, working groups of Société Française de Biologie Clinique (SFBC), Association de Langue Française pour l'Etude du Diabète et des Maladies Métaboliques (ALFEDIAM) and Société Française d'Endocrinologie (SFE) have met together, in order to analyze the national status, and to propose practical recommendations for implementing a standardization process on the basis of international experiences. It is recommended to exclusively express results as HbA1c percentage, using methods standardized and certified by comparison to reference methods such as those using Diabetes Control and Complications Trial (DCCT) values. Simultaneously, contacts have been established with manufacturers, and the realisation of periodic quality control surveys was encouraged.

A sensitive time-resolved immunofluorometric assay for the measurement of apolipoprotein B in cerebrospinal fluid. Application to multiple sclerosis and other neurological diseases.

Although low density lipoprotein receptors have been described on oligodendrocytes, apolipoprotein B was thought to be absent or present in only very small amounts in cerebrospinal fluid (CSF). Several immunoassays have been used for the measurement of apolipoprotein B in serum. However, the majority of methods cannot be used to measure small amounts of apolipoprotein B in CSF. In this study, we describe a highly sensitive time resolved immunofluorometric assay (TR-IFMA) using europium as label (detection limit: 0.3 microgram/l). The reliability of the TR-IFMA for the measurement of apolipoprotein B was first studied in serum. Serum and CSF apolipoprotein B concentrations were then determined in subjects free of neurological disorders and in patients with multiple sclerosis. Local intrathecal apolipoprotein B synthesis was calculated. Although the high sensitivity of the TR-IFMA allowed low amounts of apolipoprotein B in CSF to be detected (0.11 +/- 0.06; 0.12 +/- 0.06 mg/l in controls and multiple sclerosis patients, respectively), no apolipoprotein B could be detected in CSF by electroimmunodiffusion. As suggested by the blood/CSF apolipoprotein B ratio (about 6000), no apolipoprotein B synthesis was observed by both using apolipoprotein B index and formula. This indicates its probable serum origin. Moreover, there was no difference between controls and multiple sclerosis patients in CSF, serum, blood/CSF, index, and local intrathecal apoliprotein B synthesis. Finally, these results suggest that the role of apolipoprotein B in lipid transport in the central nervous system may be questionable.

[Respective value of glycated hemoglobin and fructosamine assays in the care of diabetes mellitus]. / Intérêts respectifs des dosages d'hémoglobine glyquée et de fructosamines dans la surveillance du diabète sucré.

The monitoring of metabolic balance in diabetes mellitus involves the assay of cumulative markers of protein glycation. Glycated hemoglobin, particularly the major component HbA1c, and fructosamine, which reflects glycated plasma protein levels, are the most commonly used parameters. Nevertheless, their utilization is still under discussion with respect to methodologies used, as well as to their respective interest in clinical diabetology. This review shows current opinion concerning the analytical and physiopathological use of these biological indicators.

Application of the time-resolved immunofluorometric assay to the study of C3 complement component glycation in vitro and in vivo.

A time-resolved immunofluorometric assay (TR-IFMA) was used for the measurement of glycated C3. The very high sensitivity of this technique allowed the direct measurement of glycated and non-glycated proteins (especially C3) in chromatography eluates. C3 glycation in vitro after incubation with 20 mmol/l glucose was always less than 3.5% by day 5. As determined with the TR-IFMA, the means +/- standard deviations of glycated C3 were 0.20% +/- 0.04 for non-diabetic subjects and 0.88% +/- 0.06 for insulin-dependent diabetic patients. The low percentages of glycated C3 in both our in vitro and in vivo studies show that this protein is subject to only moderate rates of glycation.