Review: Allergen immunotherapy reduces asthma symptoms and medications
ACP J Club. 1995 Sept-Oct;123:39. doi:10.7326/ACPJC-1995-123-2-039
Abramson MJ, Puy RM, Weiner JM. Is allergen immunotherapy effective in asthma? A meta-analysis of randomized controlled trials. Am J Respir Crit Care Med. 1995 Apr;151:969-74.
To determine whether allergen immunotherapy reduces asthma symptoms or the need for medications or improves lung function and bronchial hyperreactivity in adults with asthma.
English-language studies were identified with MEDLINE (1966 to 1990) using the terms allergen immunotherapy, desensitization, and asthma and through bibliographies of textbooks and relevant papers.
Studies were selected if they were double-blind (patients and investigators), placebo-controlled, randomized trials. Excluded studies compared different immunotherapy regimens, used untreated control groups, or studied allergen-antibody complexes or inhaled immunotherapy.
Data were extracted on asthma symptoms, medications, lung function, bronchial hyperreactivity, allergen solutions, age of participants, and adverse effects. Data extraction was done in duplicate.
20 trials were included (9 dealing with the house dust mite allergen, 5 with pollen, 5 with animal dander, and 1 with mold). Compared with placebo, dust mite immunotherapy involving 286 patients reduced symptoms (odds ratio [OR] 2.7, 95% CI 1.7 to 4.4) reduced medications (OR 4.2, CI 2.2 to 7.9) and led to a reduction in bronchial hyperreactivity (OR 13.7, CI 3.8 to 50.0). Combining data for animal dander, pollen, and mold immunotherapy involving 140 patients improved asthma symptoms (OR 4.8, CI 2.3 to 10.1) and bronchial hyperreactivity (OR 5.5, CI 2.8 to 10.7). When all studies were combined, patients receiving immunotherapy had improved asthma symptoms (OR 3.2, CI 2.2 to 4.9) and bronchial hyperreactivity (OR 6.8, CI 3.8 to 12.0). A mean of 32% of patients receiving active immunotherapy had systemic reactions compared with 18% of patients receiving placebo. Heterogeneity was shown for the effect of mite immunotherapy on symptoms but not for the nonmite studies or all studies combined. The mean effect size for immunotherapy on continuous outcomes was 0.71 (CI 0.43 to 1.00) (a mean of 7.1% predicted improvement in forced expiratory volume in 1 s).
Allergen immunotherapy improves asthma symptoms and bronchial hyperreactivity. Dust mite immunotherapy is associated with reduced medication requirements. One third of patients with asthma have adverse reactions from immunotherapy.
Source of funding: None.
For article reprint: Dr. M.J. Abramson, Department of Epidemiology and Preventive Medicine, Monash Medical School, Alfred Hospital, Prahran, Victoria 3181, Australia. FAX 61-3-9903 0556.
Many studies during the past 40 years have shown statistically and clinically significant dose-dependent benefit with allergen immunotherapy. Most, however, focused on patients with allergic rhinitis because asthma is more multifactorial. Consequently, controversy has existed on the utility of allergen immunotherapy in asthma management (1). Recent studies show that immunotherapy can inhibit late-phase response and may work through induction of T-cell tolerance (2); in contrast to medication that affects only symptoms, immunotherapy can favorably affect the disease process that underlies asthma symptoms.
The meta-analysis by Abramson and colleagues contributes to the substantial evidence that allergen immunotherapy is efficacious and safe for properly selected patients with asthma. Studies are also being done that show the cost-effectiveness of allergen immunotherapy (3); other studies are being done with modified antigens that offer less risk for anaphylaxis (1). These studies offer the promise of advancing the practice of allergen immunotherapy for asthma, which is now unambiguously established as “science” as well as “art.”
Identifying patients with asthma who will benefit from allergen immunotherapy requires documenting allergic potential by cutaneous or in vitro testing, establishing a corroborative history, and determining that avoidance measures combined with appropriate medication are undesirable, unfeasible, or ineffective in achieving optimal asthma control (1, 4, 5).
In the United States, 7 to 10 million immunotherapy injections are given each year (4). Because adverse reactions are not uncommon, immunotherapy should be given only in a setting in which adequate precautions are taken and life-threatening anaphylaxis can be treated (4, 5).
David M. Lang, MD
The Medical College of Pennsylvania and Hahnemann University Philadelphia, Pennsylvania, USA
2. Varney VA, Hamid QA, Gaga M, et al. Influence of grass pollen immunotherapy on cellular infiltration and cytokine mRNA expression during allergen-induced late-phase cutaneous responses. J Clin Invest. 1993;92:644-51.
Update for 2000
In an updated meta analysis of 62 randomized control trials, Abramson and colleagues (1) found that patients with asthma randomized to receive inhalant allergen immunotherpay experienced fewer symptoms, had less medication reliance, and exhibited reductions in nonspecific and allergen-specific bronchial hyperresponsiveness. Other more recent studies have supported the contention that allergen immunotherapy can modify long-term asthma outcomes by reducing symptoms (2) and lowering the likelihood of de novo allergen sensitization (3). Recent work in this area has also provided additional insights into the immunopathogenesis of asthma and will direct development of targeted immunologic treatment approaches to asthma management (4).
2. Cools M, Van Bever HP, Weyler JJ, Stephens WJ. Long-term effects of specific immunotherapy, administered during childhood, in asthmatic patients allergic to either house dust mite or to both house dust mite and grass pollen. Allergy. 2000;55:69-73.
3. Des Roches A, Paradis L, Menardo JL, et al. Immunotherapy with a standardized dermatophagoides pteronyssinus extract. VI. Specific immunotherapy prevents the onset of new sensitizations in children. J Allergy Clin Immunol. 1997;99:450-3.