Enzyme-potentiated desensitization in children with asthma and mite allergy: a double-blind study

The aim of this study was to evaluate the efficacy and safety of enzyme-potentiated desensitization (EPD) in children with asthma. Twenty asthmatic children (14 males and 6 females; median age: 8.5 years) were included in the study. They had positive skin tests to Dermatophagoides pteronyssinus (Dpt), no history of other allergy and had suffered from asthma for at least two years. The children were examined before starting the trial, at the first EPD dose, after 8 weeks, at the second EPD dose and 3 months after the second EPD dose. Blood samples for PRIST and RAST were drawn before the first and at the second EPD dose, and at the last follow-up. Conjunctival provocation tests (CPT) and skin test endpoint determinations were performed with dilutions of a freeze-dried Dpt extract (10-100,000 SQ-U/ml) at the start of the trial and at the last follow-up. Parents kept a diary record of the days with asthma and daily drug usage. The children were randomized to receive either two intradermal placebo injections or the active material with an 8-week interval (November 1991 and January 1992). Ten children received EPD and 10 children placebo. The intradermal injection of EPD (0.05 ml) contained 0.01 ml of beta-glucuronidase (40 Fishman units) and 0.04 ml of a mixture of inhalant allergens (1 Noon unit). The placebo injection consisted of buffer solution only. The EPD-treated children had significantly fewer days with asthma (p = 0.00000). In addition, the EPD-treated children used significantly less medication for the management of asthma attacks (p = 0.00000). At the start of the trial, three out of 10 children in the EPD group and two out of 10 in the placebo group reacted only to the highest dose of allergen used in the CPT (100,000 SQ/ml) (NS). At the last follow-up, the threshold dose in the CPT was 100,000 SQ/ml or more in nine out of 10 children in the EPD group and in four out of 10 children of the placebo group (p = 0.0349). At the last follow-up, one child in the EPD group had a negative CPT with all doses tested. Global clinical evaluation by the investigators showed that eight out of 10 EPD-treated children improved, in comparison with three out of 10 children in the placebo group (p = 0.0349). Assessment by the parents was six out of 10 and four out of 10 improved, respectively (NS). Specific IgE to Dpt, total IgE and skin prick test endpoints before and after EPD showed no significant changes. One child in the placebo group experienced mild urticaria several hours following the second injection. No other local or systemic side effects were reported. The results of the present study provide further data on the effectiveness and safety of EPD in patients with asthma.