Cetuximab, a chimeric mouse-human IgG1 monoclonal antibody against the epidermal growth factor receptor, has proven effective in the treatment of metastatic colorectal cancer and squamous cell carcinoma of the head and neck. However, a high incidence of immediate hypersensitivity reactions (HSR) to cetuximab after the first infusion has been observed. We have developed a test for identification of patients likely to show treatment-related HSR to cetuximab. An enzyme-linked immunosorbent assay (ELISA) for detecting anti-cetuximab IgEs was developed and tested on serum samples collected from cancer patients before start of cetuximab treatment, and from healthy blood donors. Similar levels of anti-cetuximab IgE were detected in pre-treatment patient sera (24/92, 26.1%) and sera from healthy blood donors (33/117, 28.2%). HSR were observed in 14 out of the 92 patients (15.2%), and 8 of these (57.1%) were grade 3-4. Anti-cetuximab IgEs were detected in 7/8 of the patients (87.5%) with severe HSRs as compared with 14/78 patients (17.9%) with no HSR (p=0.0002). Predictive value of the anti-cetuximab IgE test for HSR events of grades 3-4 was calculated using Receiver Operating Characteristics analysis. With a cut-off value of 29 arbitrary units for the anti-cetuximab IgE, the ELISA test showed a sensitivity of 87.5%, specificity of 82.1%, positive predictive value of 33.3% and negative predictive value of 98.5%. Anti-cetuximab IgE ELISA detection could be a valuable tool to help the physician anticipate an anaphylaxis episode following cetuximab infusion and opt for a suitable alternative treatment.
SummaryThe performances of nine commercial kits and an in-house method (HM) for the quantitation of anticardiolipin antibodies (ACA) have been evaluated in a multicenter study. Ninety control and patient samples and six standards from Louisville University were run with kits and with the HM. Marked differences in positivity rate between kits were observed, ranging from 31 to 60% for IgG and 6 to 50% for IgM. Concordance between kits occurred in 59 and 51% of samples for IgG and IgM respectively. Concordance coefficients (kappa) ranged from 0.13 to 0.92. Slopes of regression lines between the declared units of Louisville standards and the units measured from the calibrators of the kits showed great diversity and ranged from 0.159 to 0.931 for IgG and from 0.236 to 0.836 for IgM. The β2-glycoprotein I (β2-GPI) content of the dilution buffers and the wells supplied with the kits revealed noticeable differences. However samples containing anti-(β2-GPI antibodies were classified similarly by all but one kit. In contrast the ability to measure samples devoid of anti-β2-GPI antibodies differed markedly between the kits.This study shows that differences in positivity rates between the commercial kits may contribute to the differences in ACA prevalence rate found in the literature. The choice of cut-off levels may partly explain the moderate concordance between the kits. In addition some samples behave very differently depending on the kits. In spite of the expression of results in PL units, standardization of ACA assays has not been achieved.
SUMMARY Anticardiolipin antibodies (aCL) were investigated in 137 individuals chronically exposed to malaria and living in Africa and Asia. They belonged to several groups according to parasite (Plasmodium falciparum or vivax) and clinical manifestations (i.e. asymptomatic parasite carriers, acute uncomplicated attack or severe malaria episodes). aCL were measured in an enzyme immunoassay (ELISA) performed in the presence of either goat serum (aCLs) or gelatin (aCLg). In a group of 53 patients with autoimmune manifestations (i.e. antiphospholipid syndrome and/or lupus), detection of IgG but not IgM aCL was markedly reduced in the presence of gelatin. In malaria donors, high prevalence of serum co‐factor‐independent IgG and IgM were detected, and the presence of goat serum in the assay consistently decreased their detection. aCLg levels were found to be related to the clinical/endemic status of donors. IgG aCLg were found to be higher in asymptomatic P. falciparum carriers than in patients with uncomplicated acute or cerebral malaria. IgM aCLg were higher in the cerebral malaria group than in groups with uncomplicated acute malaria patients or asymptomatic individuals. Data suggest that using a serum co‐factor independent, sensitive ELISA, aCL are commonly detected during malarial infections and related to malarial infection status.
IgE multiple myeloma is a rare disease characterized by a high frequency of Bence-Jones proteinuria and plasma cell leukaemia when compared to other isotypes of monoclonal proteins. Only 35 cases have been reported. We describe a 70-year-old woman with a stage III IgE kappa multiple myeloma presenting with a sacral plasmacytoma. Immunological and biochemical studies showed IgE kappa producing tumoral plasma cells. Serum total IgE was high without clinical symptoms suggesting an hyperIgE syndrome or mast cell activation. The patient underwent surgical removal of the sacral tumor and monthly melphalan-prednisone treatment together with intravenous pamidronate infusions. Magnetic Resonance Imaging (MRI) of the dorsolumbar spine revealed an epidural process leading to T6-T9 radiotherapy. Bone densitometry showed a decreased bone mineral content supporting the management of myeloma-related osteoporosis with bisphosphonate infusions. A good partial response with plateau-phase and increase of bone mineral content was achieved after 1 year of treatment and still persists after a 28 months follow-up.
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