Skin Prick Tests and Allergy Diagnosis

Skin testing remains an essential diagnostic tool in modern allergy practice. A signifi cant variability has been reported regarding technical procedures, interpretation of results and documentation. This review has the aim of consolidating methodological recommendations through a critical analysis on past and recent data. This will allow a better understanding on skin prick test (SPT) history; technique; (contra-) indications; interpretation of results; diagnostic pitfalls; adverse reactions; and variability factors.

Drug Provocation Tests to Betalactam Antibiotics: Experience in a Paediatric Setting

Background: Few studies have been performed in children withs uspected betalactam allergy.We aimed to assess the role of the drug provocation test(DPT)with betalactams in a paediatric setting and to study the association between allergy to betalactam antibiotics and other allergic diseases. Methods:We included all the patients under 15 years old who were consecutively referred to the Immunoallergy Department, Dona Estefânia Hospital,Portugal(January 2002 to April 2008)for a compatible history of allergic reaction to betalactam. All were submitted to a DPT.Children were proposed to performs kintests(ST)to betalactam antibiotics followed by DPT. If they decline ST,a DPT with the culprit drug was performed. Results: We studied 161 children,60%were boys,with a median age of 5years old at the time of the DPT.Thirty-three patients(20.5%)had an immediate reaction and 33(20.5%)a non-immediate reaction. These verity of there porte dreactions was low in most cases. Skin tests to betalactams were performed in 47 children and were positive in 8.DPT was positive inonlyone(3.4%)of the patients skin tested and in 11(13.4%)of those not skin tested. These verity of the DPT reaction was low.Asthma and food allergy were associated with a positive DPT in the later group. Conclusions: DPT seems a safe procedure even in the absence of ST in non-severe cases. This could be a practical optionin infants and pre-school children,where ST are painful and difficult to perform.Additional caution should be taken in children with asthma and food allergy.

Methacholine Dose-Response Slopes from Maximal Bronchial Challenge Tests in Asthmatic Children: Methodological Aspects

To determine whether the slope of a maximal bronchial challenge test (in which FEV1 falls by over 50%) could be extrapolated from a standard bronchial challenge test (in which FEV1 falls up to 20%), 14 asthmatic children performed a single maximal bronchial challenge test with methacholin(dose range: 0.097–30.08 umol) by the dosimeter method. Maximal dose-response curves were included according to the following criteria: (1) at least one more dose beyond a FEV1 ù 20%; and (2) a MFEV1 ù 50%. PD20 FEV1 was calculated, and the slopes of the early part of the dose-response curve (standard dose-response slopes) and of the entire curve (maximal dose-response slopes) were calculated by two methods: the two-point slope (DRR) and the least squares method (LSS) in % FEV1 × umol−1. Maximal dose-response slopes were compared with the corresponding standard dose-response slopes by a paired Student’s t test after logarithmic transformation of the data; the goodness of fit of the LSS was also determined. Maximal dose-response slopes were significantly different (p < 0.0001) from those calculated on the early part of the curve: DRR20% (91.2 ± 2.7 FEV1% z umol−1)was 2.88 times higher than DRR50% (31.6 ± 3.4 DFEV1% z umol−1), and the LSS20% (89.1 ± 2.8% FEV1 z umol−1) was 3.10 times higher than LSS 50% (28.8 ± 1.5%FEV1 z umol−1). The goodness of fit of LSS 50% was significant in all cases, whereas LSS 20% failed to be significant in one. These results suggest that maximal dose-response slopes cannot be predicted from the data of standard bronchial challenge tests.

Evidence for Nevirapine Bioactivation in Man: Searching for the First Step in the Mechanism of Nevirapine Toxicity

Despite its efficacy, including in the prevention of vertical transmission, the antiretroviral nevirapine is associated with severe idiosyncratic hepatotoxicity and skin rash. The mechanisms underlying nevirapine toxicity are not fully understood, but drug bioactivation to reactive metabolites capable of forming stable protein adducts is thought to be involved. This hypothesis is based on the paradigm that drug reactive metabolites have the potential to bind to self-proteins, which results in drug-modified proteins being perceived as foreign by the immune system. The aim of the present work was to identify hemoglobin adducts in HIV patients as biomarkers of nevirapine haptenation upon bioactivation. The ultimate goal is to develop diagnostic methods for predicting the onset of nevirapine-induced toxic reactions. All included subjects were adults on nevirapine-containing antiretroviral therapy for at least 1month. The protocol received prior approval from the Hospital Ethics Committees and patients gave their written informed consent. Nevirapine-derived adducts with the N-terminal valine of hemoglobin were analyzed by an established liquid chromatography-electrospray ionization-tandem mass spectrometry method and characterized on the basis of retention time and mass spectrometric fragmentation pattern by comparison with adduct standards prepared synthetically. The nevirapine adducts were detected in 12/13 patient samples, and quantified in 11/12 samples (2.58±0.8 fmol/g of hemoglobin). This work represents the first evidence of nevirapine-protein adduct formation in man and confirms the ability of nevirapine to modify self-proteins, thus providing clues to the molecular mechanisms underlying nevirapine toxicity. Moreover, the possibility of assessing nevirapine-protein adduct levels has the potential to become useful for predicting the onset of nevirapine-induced adverse reactions.