Subcutaneous immunotherapy not linked to severe reactions in severe asthma
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Key takeaways:
- The total patient population experienced a rate of 19.9 severe reactions per 10,000 injection visits.
- Patients with severe asthma experienced a rate of 23.9 severe reactions per 10,000 injection visits.
- The patients who did not have asthma and the patients with severe asthma did not experience any difference in rates of grade III or IV severe reactions.
Patients with severe asthma who are on subcutaneous immunotherapy for allergy treatment do not experience an increased risk for moderate to severe systemic reactions, according to a study published in Annals of Allergy, Asthma & Immunology.
However, further studies are needed to identify factors that may influence rates of severe reactions in this population, Timothy G. Chow, MD, of the division of allergy and immunology in the department of internal medicine at the University of Texas Southwestern Medical Center, and colleagues wrote.
The population included 65,855 patients (mean age, 32.5 ± 20.4 years; 58.1% female) treated in a multicenter national network of single-specialty private allergy practices between January 2015 and December 2019.
While 55.6% of these patients had no asthma diagnosis, 16.3% had mild intermittent asthma, 9.9% had mild persistent asthma, 8.5% had moderate persistent asthma, 5.6% had other or unspecified asthma, 2.5% had exercise-induced bronchospasm and 1.6% had severe asthma.
Providers administered 4,815,506 subcutaneous immunotherapy injections across 2,290,908 visits. Specifically, 1,072 patients with severe asthma received subcutaneous immunotherapy.
There were 4,415 systemic reactions overall for a rate of 19.9 systemic reactions per 10,000 injection visits. Patients with severe asthma had 23.9 systemic reactions per 10,000 injection visits (incidence rate [IR], 0.239; 95% CI, 0.189-0.298). Those with no asthma had 16.8 systemic reactions per 10,000 injection visits (IR, 0.168; 95% CI, 0.161-0.175).
The overall systemic reaction total included 155 grade III or IV systemic reactions, with patients with severe asthma experiencing four (5.1%) of the grade III reactions and one (1.3%) of the grade IV reactions.
The researchers did not note any difference in rates of grade III or IV systemic reactions between the patients with severe asthma and those with no asthma, nor was there any difference in rate of total severe reactions between those with severe asthma and those with less severe asthma.
Also, 1,513 (2.3%) of the total patient population received epinephrine, including 2.1% of the patients who did not have asthma and 2.8% of the patients with severe asthma, which the researchers did not call a statistically significant difference.
Age was the only statistically significant predictor of reaction grade, the researchers said, as the likelihood of having a grade III or IV systemic reaction increased with age (B = 0.012; OR = 1.013; 95% CI, 1.003-1.002).
The patients with severe asthma had the highest increases in Asthma Control Test (ACT) scores, with an average boost of 1.92 points, at 120 days after initiation of subcutaneous immunotherapy.
None of the groups stratified by presence or severity of asthma had a decline in ACT scores from baseline to 120 days. However, the researchers cautioned that the minimum important difference for ACT scores is 3.
Based on these findings, the researchers said they did not find any association between a history of severe asthma or of poorly controlled asthma and increased rates of grade III of IV severe reactions, indicating that these histories would not necessarily contraindicate subcutaneous immunotherapy initiation.
But the researchers also warned that their data does not support the administration of subcutaneous immunotherapy to patients who have poorly controlled asthma on the day of that administration, as poorly controlled asthma has been well established as a risk factor for severe or fatal reactions due to subcutaneous immunotherapy.
Further prospective studies, the researchers concluded, would be necessary to identify modifiable risk factors that could influence the rate of severe systemic reactions among patients who have severe asthma.
Perspective
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The results are somewhat surprising in that the rate of systemic reactions was not higher in the severe asthma group, although several factors could be playing a role here.
It is important to understand the difference between asthma severity and asthma control. As the authors noted, this paper does not provide evidence for administering subcutaneous immunotherapy in patients with uncontrolled asthma. Even though the initial diagnosis was severe asthma, with poor control based on the ACT scores, I am sure that the allergists made other changes in asthma care to improve control. Patients may present with severe asthma, but really have undertreated asthma.
There is a potential for bias, as this was a retrospective study, and the diagnosis of severe asthma was based on diagnosis codes. Such severity assessments are usually made on the initial visit, and the practitioner may not have updated or changed them, which has been my experience.
In addition, the severe asthma patients were started on lower doses of subcutaneous immunotherapy, and most did not achieve their maintenance dose. Systemic reactions may be lower when doses of antigen are lower.
There was also a trend toward increased systemic reactions with increasing asthma severity, and patients with asthma of any severity had a higher rate of more severe systemic reactions. Additionally, the small number of severe reactions, particularly in the patients with severe asthma, makes a definite conclusion difficult.
I generally do not prescribe subcutaneous immunotherapy for patients with severe asthma, although in those occasions where I do, it is only in those with controlled severe asthma. In that population, I would say my experience resembles the results of the study.
Subcutaneous immunotherapy may be safe in patients with severe asthma, but more research is needed. This is not evidence for providing subcutaneous immunotherapy to patients with uncontrolled asthma, regardless of severity.
Next, research should include large, controlled trials of subcutaneous immunotherapy in patients with standardized criteria for asthma severity and standardized subcutaneous immunotherapy regimens.
Finally, the data on the efficacy of subcutaneous immunotherapy in asthma patients is contradictory. The evidence for improvement in ACT and Childhood ACT scores in this study may have not been related to subcutaneous immunotherapy, but to other therapies given to the patients. If you are going to administer subcutaneous immunotherapy to asthma patients of any severity, be sure that the history supports the allergens as triggers of asthma and make sure that asthma control is assessed on each injection day.
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