Superiority of radiobinding assay over ELISA for detection of IAAs in newly diagnosed type I diabetic children.

OBJECTIVE: Liquid- or solid-phase assays have been used for insulin autoantibody (IAA) determination, and the method of IAA measurement has not been standardized. RESEARCH DESIGN AND METHODS: IAAs were determined by radiobinding assay (RBA) and enzyme-linked immunosorbent assay (ELISA) in two large age-matched groups of nondiabetic and newly diagnosed insulin-dependent (type I) diabetic children. RESULTS: Positivity for IAA by RBA (greater than or equal to nondiabetic mean + 3SD) was 2 of 178 (1.1%) and 55 of 173 (32%) in nondiabetic and diabetic children, respectively. Prevalence of IAA by RBA was significantly higher in the youngest age-group (63% between 0-4 yr). Positivity for IAA by ELISA was 1 of 178 (0.6%) and 8 of 169 (4.7%) in nondiabetic and diabetic children, respectively. Concordance rates between both assays were 0 of 3 (0%) in control subjects and 5 of 58 (8.6%) in diabetic children. CONCLUSIONS: We conclude that RBA is more appropriate than ELISA for IAA detection at the onset of the disease. In addition, because available data suggest that IAAs detected by RBA only are high-affinity antibodies, it is tempting to speculate that IAAs reflect a mature immune reaction against endogenous insulin.

[Peri- and postoperative use of low molecular weight heparin in peripheral vascular surgery]. / Utilisation per et postopératoire d'une héparine de bas poids moléculaire en chirurgie vasculaire périphérique.

A pilot study has been conducted in ten consecutive patients undergoing femoro-popliteal reconstruction or distal vascular surgery under epidural anaesthesia. Immediately before arterial cross-clamping, enoxaparin (E) (75 anti-Xa IU.kg-1) was injected intravenously (i.v.). During surgery, washing of the saphenous or polytetrafluoroethylene (PTFE) graft has been performed using enoxaparin. Enoxaparin (75 anti-Xa IU.kg-1) was administered subcutaneously (S.C.) 8 hours after the i.v. injection, and then every 12 hours during 10 days. The patency of the vascular reconstruction and the side-effects of E administration were evaluated clinically before and during surgery, then by a daily clinical examination. Echo-Doppler and/or arteriography were also performed preoperatively and on the 10th postoperative day. Haematocrit, platelet count, activated partial thromboplastin time, prothrombin time, thrombin time, fibrinogen and anti-Xa activity were assessed. None of the patients developed venous or arterial thrombosis and all the by-pass grafts remained patient. Only one minor surgical bleeding occurred on the first post operative day, despite anti-Xa levels in the expected range. One patient developed minor haematomas at the injection site. No bleeding was observed. Further randomized studies comparing LMWH and UH are required in order to substantiate these preliminary clinical and biological findings.

[Insulin autoantibodies and insulin-induced antibodies in children with insulin-dependent diabetes]. / Auto-anticorps et anticorps induits anti-insuline chez l'enfant diabétique insulino-dépendant.

AIM OF THE STUDY: The aim was to study the time course of development of insulin antibodies during the first months of treatment in diabetic children, under human insulin therapy, and to see whether the presence of insulin autoantibodies influenced the subsequent binding to insulin. METHODS: Anti-insulin antibodies were measured using a radio-binding assay in 16 diabetic children, aged 4-13 years, before the first insulin injection and at regular intervals until the 9th month of treatment. RESULTS: Insulin autoantibodies were detected in 11 out of the 16 children at the time of diagnosis. Binding to insulin increased significantly after one month of treatment in these children, and after 2 months in the children with no insulin autoantibodies at diagnosis. After 2 months insulin therapy, all the children demonstrated antibodies against insulin. Insulin binding at 9 months was not correlated to the baseline values. Anti-insulin antibodies develop rapidly and frequently under human insulin, and are not influenced by the presence of insulin autoantibodies.

Protein A-sepharose used to measure free insulin in plasma.

Diabetic patients receiving insulin therapy generally develop anti-insulin antibodies that must be eliminated, usually by extraction with polyethylene glycol (PEG), before determining the concentration of free (active) insulin in plasma. We describe a new method for removing such antibodies, with the use of Protein A coupled to Sepharose microspheres. The results correlate well with those by the PEG method, although values are systematically higher or lower for given samples, according to the initial titer of the antibody measured in terms of binding capacity. Further studies are required to clarify this observation.