Diagnosis of atopic conditions in the tropics

Controversy surrounds studies of the incidence and clinical importance of atopic disease in tropical populations. This could be due in part to the methods of evaluation employed. The value of some of the tests commonly used in the diagnosis of atopic disease was therefore examined in a tropical situation. Extracts of environmental allergens are usually obtained from suppliers located in more temperate regions of the world, and skin tests, the radio-allergosorbant test (RAST) and RAST-inhibition demonstrate that these can lack important tropical allergens. In addition, although some local extracts are used in clinical practice, these have great variability in their protein content, allergenicity and toxicity. In the tropical environment serum IgE levels can have a greater relation to intestinal helminthic infestation than to atopic disease, even after anti-parasitic treatment, and thus the definition of "normal" IgE values must take into account the socio-economic status of the groups examined. The helminth-induced elevation of total serum IgE levels can also cause false-positive RAST results.