A trial of house dust mite extract in bronchial asthma. Mite Allergy Subcommittee of the Research Committee of the British Thoracic Association.

Patients with asthma considered to be due to house dust mite allergy were allocated at random to treatment with (a) increasing weekly injections of house dust mite extract for 18 weeks followed by monthly injections to complete 18 months of treatment; (b) similar injections for 18 weeks followed by placebo injections up to 18 months or (c) placebo injections for 18 months. Fifty-six patients completed at least six months of observation. In patients not on corticosteroids the treated group did a little better than the controls as judged by night asthma scores, discontinuation of bronchodilators and overall blind assessment of the records by a panel of independent physicians. No benefit was apparent by extending treatment from 18 weeks to 18 months. In contrast, patients on corticosteroids given placebo injections did a little better than the treated group. The extract used was stronger than the commercially available preparation and the injections had to be stopped in one-sixth of the patients because of side-effects. The improvement in patients not on corticosteroids in this trial was of doubtful clinical importance.