Transcutaneous bilirubin measurement in preterm infants]

Transcutaneous bilirubinometry is an effective screening tool for neonatal jaundice in full-term babies. But its accuracy is not shown yet in preterm infants. METHODOLOGY: We carried out a prospective study in a neonatal intensive care unit. The study included 47 preterm infants. From birth, a transcutaneous bilirubin measurement (BTc) using the BiliCheck was made on the forehead of each newborn every 8 h. Blood sampling for determination of total serum bilirubin (BS) was combined with BTc: 1) if value of BTc was higher than limits values for phototherapy; 2) on the second day of life and 3) 4 hours after cessation of phototherapy. RESULTS: Mean gestational age was 30 week and mean birth weight was 1419 g. We studied 151 pairs of BTc and BS. Mean values obtained by BTc and BS were respectively 160.6+/-50 mumol/L and 190.6+/-61.4 mumol/L. A significant correlation between BTc and BS was found. But the limits of agreement were very wide. The negative predictive value (NPV) of BTc was above 90% in each group of gestational age. DISCUSSION: The need for phototherapy cannot be determined by BTc in preterm infants. But the BTc is reliable when its value is under the limits for phototherapy. CONCLUSION: With a very high incidence of neonatal jaundice (87%) in our cohort, a value of BTc under the limits for phototherapy has a good NPV in preterm infants.     

Radioimmunoassay method for the detection of IgE antibodies specific to alcuronium

A radio-immunoassay (RIA) was used to screen for specific IgE to myorelaxants. Alcuronium was coupled to epoxy-activated Sepharose. Sixteen patients with anaphylaxis to alcuronium (n = 2), gallamine (n = 2) or suxamethonium (n = 12) were studied. The diagnosis was established by intradermal tests (ID), passive cutaneous anaphylaxis tests and human basophil degranulation tests. The amount of non specific label retained by Sepharose-ethanolamine (with sera of patients) and Sepharose-alcuronium (with sera of 11 control subjects) was estimated. The RIA was positive 10/16 (8/14 patients having reacted to a muscle relaxant other than alcuronium). The RIA seemed to be useful in the diagnosis of anaphylaxis to muscle relaxants. Drug-reactive antibodies were specific of the quaternary ammonium radical, which was the common allergenic determinant of all molecules of muscle relaxants. This test accounted for in vitro cross-reactivity, but had no predictive value for the clinical risk of crossed-anaphylaxis. This risk was best assessed by ID; it was positive in three cases. Although it was not possible to compare ID and RIA, the interpretation of which was different, both tests should be recommended for the detection of sensitivity to muscle relaxants.     

Les plantes transgéniques (OGM végétaux) : connaissances et inconnues sur les risques d'allergénicité…

Much attention is now being focused on foods from genetically modified plants because of the risk of allergenicity. No such risk has been reported for the first generation of GM plants made resistant to herbicides and insect larvae. Current experiments with hypoallergenic GM plants are reported and discussed in the present paper. The second generation of GM plants will improve the nutritional aspects of natural foods. Transgenic proteins could reach from 4 up to 8% of the total protein content in these foods. Any potential difference in allergenicity between second generation GM plants and the natural varieties must be examined with respect to the risk for food allergy caused by food products made from these plants and the risk for respiratory allergies in the people living near the crops caused by airborne pollen originating from the plants. WHO–FAO directives as well as the Codex Alimentarius proposals and the European Food Safety Authority (EFSA) guidelines recommend that transgenic proteins be screened for homology (by in silico study) and cross-reactivity with known allergens, as well as being examined carefully for modifications of host-plant proteomes. In vivo animal studies are also to be carried out to assess any potential immunogenicity. Lacking adequate safety data, the absence of potential allergenicity of transgenic plants cannot be ruled out. This is why data that do not meet the recommended safety criteria required for commercialization of GM plants do not allow us to rule out absolutely the risk that may be associated with products that are going to be commercialized. Therefore, it is essential that commercialized GM plants be monitored. We propose the establishment of public reference serum banks based on up-to-date WHO–FAO recommendations concerning the selection of sera according to precise criteria. We also propose establishing a system of allergovigilance linking national and European health and food safety agencies and a network of university hospital-based clinical and laboratory reference centres, together with a network of clinical allergists, responsible for the creation of the serum banks. Allergists working through these networks would be able to identify new sensitizations to transgenic foods in the population, just as they now identify new types of food allergies, which, in this case, would be GM foods. Such a project is now being established in France.     

Recognition of an extensive range of IgE-reactive proteins in cod extract

Allergy to fish is one of the most common food allergies. Gad c 1 is the only fish allergen which has been purified and characterized. Other allergens have been detected by Western blot in cod extracts. We have now improved the Western-blot procedure in order to characterize fish IgE-reactive proteins from extracts prepared under different conditions: pre-rigor mortis and postrigor mortis. EDTA addition or not. and DEAE ion-exchange chromatography. Several IgE-reactive protein bands have been identified over a wide molecular-weight range. In particular, the 104- and 130-kDa IgEreactive protein bands were detected. These new bands may correspond to aggregates, as EDTA increased the relative amount of the 60-, 67-, 104-, and 130-kDa IgE-reactive protein bands in Western blot. All these bands were also detected by an antiparvalbumin monoclonal antibody, specific to the first calcium-binding site. The longer period of storage increased the relative amounts of the 41-, 80-, 104-. and 130-kDa IgE-reactive protein bands. The 18-kDa band was detected only in fish stored for several days. In conclusion, we have described IgE-reactive protein bands over a wide molecular-weight range (12–130 kDa) in Western blot of cod extract, and shown that EDTA and storage conditions may influence the relative distribution of IgE-reactive protein bands.     

Cox proportional hazards survival regression in haplotype-based association analysis using the Stochastic-EM algorithm

It is now widely recognized that haplotype information inferred from genotypes can be of great interest to better characterize the role of a candidate gene in the etiology of a complex trait in the context of association studies. Several works have recently advocated the simultaneous estimation of haplotype frequencies and haplotype effects in order to get a better efficiency in parameter estimation. Most of the available models can deal with a binary or a quantitative phenotype, but none has yet discussed the application of haplotype-based association analysis to a survival outcome. We describe how the recently proposed Stochastic-EM (SEM) algorithm can be applied to estimate haplotype effects in censored data analysis using a standard Cox proportional hazards formulation. This model has been implemented in the THESIAS software freely available at http://www.genecanvas.org.     

Factors affecting the determination of threshold doses for allergenic foods: how much is too much?

BACKGROUND: Ingestion of small amounts of an offending food can elicit adverse reactions in individuals with IgE-mediated food allergies. The threshold dose for provocation of such reactions is often considered to be zero. However, because of various practical limitations in food production and processing, foods may occasionally contain trace residues of the offending food. Are these very low, residual quantities hazardous to allergic consumers? How much of the offending food is too much? Very little quantitative information exists to allow any risk assessments to be conducted by the food industry. OBJECTIVE: We sought to determine whether the quality and quantity of existing clinical data on threshold doses for commonly allergenic foods were sufficient to allow consensus to be reached on establishment of threshold doses for specific foods. METHODS: In September 1999, 12 clinical allergists and other interested parties were invited to participate in a roundtable conference to share existing data on threshold doses and to discuss clinical approaches that would allow the acquisition of that information. RESULTS: Considerable data were identified in clinical files relating to the threshold doses for peanut, cows' milk, and egg; limited data were available for other foods, such as fish and mustard. CONCLUSIONS: Because these data were often obtained by means of different protocols, the estimation of a threshold dose was very difficult. Development of a standardized protocol for clinical experiments to allow determination of the threshold dose is needed.     

Food allergy diagnosis

The diagnosis of food allergies (FA) relies upon the sequential use of different means and tools, according to a decision tree. Ten clinical characteristics point to a potential FA. A diary for food consumption during a week surveys all labellings, in order to detect masked food allergens. The second step is based on skin prick tests to natural foods, and epicutaneous tests to a few proteins (casein, gluten...). Biological tests using multi detection tests of specific IgEs to numerous allergens are not advised owing to the frequency of clinically not relevant in vitro cross-reactivity. Single determination of specific IgEs, have a 95% predictive positive value of high levels in cases of allergy to milk, egg, fish and peanut, and can spare oral challenges. The primary use of biological tests is not currently advised but may be of interest in litigious cases. Standardized oral challenges are the golden standard. Eviction regimens are an alternative used for cow's milk allergy in infancy, or for suspected digestive allergies in adults.