Description of a specific bronchial provocation test for the diagnosis of occupational asthma due to platinum salts.

Occupational exposure to platinum salts may cause the onset of skin and respiratory disorders with an IgE-mediated allergic mechanism. The diagnosis of occupational asthma due to platinum salts was, in a small number of cases, achieved also via occupational specific bronchial provocation tests (sBPT), which until now were conducted by pouring platinum salt dusts from one tray to another or by direct aerosoling of hexachloroplatinate solutions into the patient's airways. Here we describe an original occupational sBPT based on atomization of solutions of ammonium hexachloroplatinate, at increasing concentrations, in a 5 m3 challenge room: the starting solution is a 1:100 dilution of the preset threshold of the patient's skin reactivity to the substance. In the absence of a bronchoconstrictive response, the following concentration is atomized (each time 10 times higher than the previous one), until the maximum concentration, 10(-2) M, is reached. The patient is not in the challenge room during atomization of the solutions, but enters when this operation has been completed and remains there for 15 minutes, unless he/she shows signs of respiratory trouble before that time. After each exposure, the patient is clinically monitored, with respiratory function tests at preset times, until at least 8 hours after the end of the exposure. The test allowed identifying a respiratory hypersensitivity specifically to platinum as cause of asthma in two precious metal workers, with the onset of immediate bronchospasm in one patient and biphasic bronchospasm in the other. Compared to the sBPT by pouring a mixture of platinum salt dusts from one tray to another, the method we designed offers a better standardization of bronchial stimulation and, compared to direct aerosoling of hexachloroplatinate into the patient's airways, it has the advantage of reproducing the respiratory risk conditions occurring in the workplace and offers better safety guarantees for the patient, since it reduces the risk of onset of serious asthmatic or even systemic responses in subjects highly hypersensitive to this metal.