Review: Allergen-specific immunotherapies reduce symptoms, medication requirements, and bronchial hyperreactivity in asthmaPDF
ACP J Club. 2004 Jul-Aug;141:18. doi:10.7326/ACPJC-2004-141-1-018
Clinical Impact Ratings
Allerg & Immunol:
Abramson MJ, Puy RM, Weiner JM. Allergen immunotherapy for asthma. Cochrane Database Syst Rev. 2003;(4):CD001186. [PubMed ID: 14583928]
In patients with asthma, how do different allergen-specific (AS) immunotherapies compare for reducing asthma symptoms, medication requirements, and improving bronchial hyperreactivity (BHR)?
Studies were identified by searching MEDLINE (1966 to December 2001), the Cochrane Airways Group trials register (up to June 2001), EMBASE/Excerpta Medica, CINAHL, and Current Contents; and scanning abstracts of dissertations and reference lists.
Study selection and assessment
Studies in any language were selected if they were randomized controlled trials (RCTs) comparing AS immunotherapy with placebo, antigenically inactive controls, untreated controls, or inhaled steroids; or comparing house dust extract with placebo. Studies were assessed for methodological quality using the Jadad scale.
Asthma symptoms, medication requirements, lung function (including peak expiratory flow rate, FEV1, and thoracic gas volume), nonspecific BHR (to histamine or methacholine), and AS BHR.
75 RCTs met the selection criteria (n = 3506). Patients who received AS immunotherapy (particularly mite, pollen, and animal dander allergens) had greater symptomatic improvement, had reduced asthma medication requirements, and were less likely to develop increased nonspecific or AS BHR than those who received placebo (Table). When compared with untreated controls, patients in the AS immunotherapy group had greater improvement in lung function (2 RCTs; weighted mean difference [WMD] −15.20 [95% CI −23.09 to −7.31]); and greater reduction in asthma symptoms (3 RCTs; WMD −6.93 [CI −13.83 to −0.04]), medication requirements (1 RCT; WMD −4.00 [CI −4.79 to −3.21]), and nonspecific BHR (1 RCT; WMD −0.77 [CI −1.11 to −0.43]). No other comparison groups differed for lung function.
In patients with asthma, allergen-specific immunotherapies reduce asthma symptoms, medication requirements, allergen-specific bronchial hyperreactivity (BHR), and the development of increased nonspecific BHR.
Source of funding: Garfield Weston Foundation, UK.
For correspondence: Associate Professor M. Abramson, Monash University, Prahran, Victoria, Australia. E-mail email@example.com.
Table. Allergen-specific immunotherapies (ITs) vs placebo for reducing asthma symptoms*
|Outcomes||Comparisons||Number of trials||Weighted event rates||RRR (95% CI)||NNT (CI)|
|Asthmatic symptoms||Mite IT vs placebo||12||30% vs 51%||38% (13 to 56)||5 (1 to 3)|
|Pollen IT vs placebo||3||21% vs 62%||75% (10 to 93)||3 (2 to 4)|
|Animal dander IT vs placebo||4||27% vs 69%||54% (6 to 78)||3 (2 to 17)|
|Overall IT vs placebo||22||29% vs 60%||49% (35 to 59)||4 (3 to 5)|
|Asthma medication requirements||Overall IT vs placebo||16||48% vs 72%||34% (24 to 42)||5 (4 to 7)|
|Nonspecific BHR||Overall IT vs placebo||5||30% vs 64%||53% (30 to 69)||3 (2 to 6)|
|Allergen-specific BHR||Overall IT vs placebo||16||32% vs 63%||49% (37 to 59)||4 (3 to 5)|
|House dust vs placebo||1||11% vs 39%||71% (29 to 88)||4 (3 to 13)|
*WMD = weighted mean difference; BHR = bronchial hyperreactivity. Other abbreviations defined in Glossary; weighted event rates, RRR, NNT, and CI calculated from data in article using a fixed-effects model. Follow-up not reported.
The updated review by Abramson and colleagues “confirms the efficacy of immunotherapy in terms of a reduction in asthma symptoms and use of asthma medication.”
This review discusses information about the benefits of immunotherapy but does not assess the risks or costs. The biggest concern is anaphylaxis. Using data from 1985 to 1992, the FDA estimated that the crude annual death rate for allergenic extracts is low—0.7 per million injections (1)—roughly similar to fatal reactions to injected penicillin, which range from 0.13 to 0.4 fatalities per million injections (2). Clearly, precautions are needed. Although local reactions for AS immunotherapy injections are common, they are simple to manage.
The second relevant consideration regarding AS immunotherapy is cost. In 1996, the cost of AS immunotherapy for the first year was estimated to be U.S. $800 per year and $170 for each year thereafter (3). In contrast, the newest therapy for asthma (Xolair) may cost U.S. $12 000 per year. Immunotherapy decreases asthma medication use, offsetting its own cost, and may also further decrease costs by limiting the need for concurrent treatment of allergic rhinitis.
Finally, a recent European study tested the hypothesis that AS immunotherapy might prevent the development of asthma. After 3 years of therapy, children with allergic rhinitis who received AS immunotherapy were about half as likely to develop asthma as those who did not (4).
AS immunotherapy is safe and effective when administered by trained health care professionals who observe high standards of care.
Bernard R. Adelsberg, MD
Hamden Internal Medicine Associates
Hamden, Connecticut, USA
2. Idsoe O, Guthe T, Willcox RR, de Weck AL. Nature and extent of penicillin side-reactions, with particular reference to fatalities from anaphylactic shock. Bull World Health Organ. 1968;38:159-88. [PubMed ID: 5302296]
3. Sullivan TJ, Selner JC, Patterson R, Portnoy J, Seligman M. Expert care and immunotherapy for asthma. A review of published studies with emphasis on patient outcome and cost. American College of Allergy, Asthma, and Immunotherapy Monograph. Nov 1996;1-25.
4. Möller C, Dreborg S, Ferdousi HA, et al. Pollen immunotherapy reduces the development of asthma in children with seasonal rhinoconjunctivitis (the PAT-study). J Allergy Clin Immunol. 2002;109:251-6. [PubMed ID: 11842293]