ABSTRACT
BACKGROUND: Erythropoietic protoporphyria (EPP) is a rare, inherited disorder of haem biosynthesis owing to deficient ferrochelatase (FECH) and accumulation of protoporphyrin IX (PPIX). This results in acute cutaneous photosensitivity upon light exposure with production of reactive oxygen species (ROS) and ultra-weak photon emission (UPE) as a by-product. We investigated if UPE evaluated the light sensitivity in EPP patients and influence of zinc treatment. METHODS: Fourteen EPP patients took zinc sulphate (3 × 200 mg/day) during spring and summer. Using a photomultiplier (PM), UPE was measured from the buttock skin and dorsal hand before and after solar-simulated light (SUN) exposure. Blood samples were analysed routinely for plasma zinc, iron, ferritin, transferrin, haemoglobin, erythrocyte PPIX and Zn-PPIX. RESULTS: UPE in EPP patients resembled that seen in healthy individuals. Without treatment, a seasonal decrease was seen from spring to summer in four control patients. However, oral zinc treatment reduced ROS formation significantly regardless of SUN exposure. After SUN exposure, the initial burst was correlated to plasma iron and erythrocyte PPIX. During treatment, an inverse correlation was found between plasma zinc concentration and the initial burst. CONCLUSION: Measurements of UPE can be used for monitoring UVA-induced oxidative processes in vivo in the skin of EPP patients.
Subject(s)
Photometry/methods , Photosensitivity Disorders/diagnosis , Photosensitivity Disorders/drug therapy , Porphyria, Erythropoietic/diagnosis , Porphyria, Erythropoietic/drug therapy , Reactive Oxygen Species/analysis , Zinc Sulfate/administration & dosage , Administration, Oral , Antioxidants/administration & dosage , Astringents/administration & dosage , Dermatologic Agents/administration & dosage , Female , Humans , Male , Photons , Photosensitivity Disorders/metabolism , Pilot Projects , Porphyria, Erythropoietic/metabolism , Reproducibility of Results , Sensitivity and Specificity , Treatment OutcomeABSTRACT
OBJECTIVE: To develop and evaluate a liquid phase immunoassay for accurate determination of allergen-specific IgE (sIgE) as a useful tool in the diagnosis of allergy patients. DESIGN AND METHODS: A fully automated, quantitative sIgE assay was developed for the ADVIA Centaur technology platform using a unique calibration method based on a recombinant reference allergen. Compared to most other IgE-assays, the assay employs a reverse sandwich architecture using monoclonal mouse anti-human IgE antibody covalently bound to paramagnetic particles in the solid phase and capturing the sample IgE. Bound sIgE reacts with liquid biotin-labeled allergen, which is detected as chemiluminescence using acridiniumester-labeled streptavidin. RESULTS: The ADVIA Centaur sIgE assay (Centaur assay) has exclusive reactivity to human IgE and performs with excellent linearity in the assay range 0.35-100 kU/L and high precision (imprecision within-run <2.6%, between-run <4.9%, and total imprecision <7.1%). The analytical sensitivity is <0.10 kU/L. Using Pharmacia CAP system FEIA (CAP) as a comparative method, positive/negative concordance was 94% at 0.35 kU/L cut-off, and the Centaur assay has a sensitivity of 90% and a specificity of 98%. Validation of the assay in a general population sample (The Copenhagen allergy study) revealed that sIgE was highly associated with a clinical diagnosis of inhalation allergy. CONCLUSIONS: The Centaur assay is an allergen-specific assay for measurement of IgE without interference from other types of immunoglobulins or nonspecific IgE. The assay performs with a linear reaction, high assay range, and good reproducibility. The assay correlates well with the CAP system and is in agreement with clinical diagnosis.