Fire-Ant Sensitive Patients Often Don’t Stick With SCIT

HOUSTON — A 3- to 5-year course of subcutaneous immunotherapy (SCIT) was highly effective for preventing anaphylaxis reactions to fire ant stings, but adherence with SCIT was very low, a researcher reported here.

Just 23% of study participants completed 3 years of SCIT, with relocation and fear of shot reactions reported as reasons for discontinuing treatment, according to Brittanie Neaves, MD, of JBSA-Lackland Air Force Base in Lackland, Texas.

The study is among the first to examine fire ant SCIT adherence, she reported at the American College of Allergy, Asthma, & Immunology (ACAAI) annual meeting.

The red imported fire ant (IFA, Solenopsis invicta) is native to Central and South America, but they are now commonly found in the U.S. in Southern and Southwestern states.

IFA stings, while painful, are not often serious. But anaphylaxis deaths have occurred in people who are highly sensitized to fire ant bites. One survey-based study reported 83 deaths out of around 29,000 patients treated for fire ant stings.

IFA SCIT is currently the only disease-modifying treatment available for people who are highly sensitized to bites from the insect.

“It has been shown to decrease the systemic reaction rate to approximately 2%, but for optimal protection, therapy should be continued for at least 3 to 5 years,” Neaves said. “Successful clinical outcomes require commitment both to initiate and sustain adherence to immunotherapy. Non-adherence to clinical therapies has long been a problem, especially for prophylactic or suppressive treatments.”

She noted that studies examining allergen SCIT show non-adherence rates as high as 50%.

“The objective of this study was to assess how patients in an IFA-endemic area adhered to the recommendation to complete a 3- to 5-year course of SCIT,” she said. “I also wanted to look at factors that may affect patient adherence to this potentially life-saving treatment.”

The prospective, observational study involved patients who had previously experienced systemic reactions to IFA, had IFA-specific IgE determined by skin testing or serology, and who had been recommended by an allergist, or other healthcare professional, for a 3 -to 5-year course of IFA SCIT.

Study participants were contacted annually by telephone to determine if they were still on IFA SCIT. If not, they were asked their reason or reasons for discontinuing the therapy.

Among the study participants, 11% had mild initial reactions in skin or serology testing, 76% had moderate reactions, and 13% had severe initial reactions.

At 3 and 5 years, respectively, 23% and 13% of patients not lost to follow-up were still receiving IFA SCIT.

Subgroup analysis at 3 years showed no statistically significant difference in adherence between males and females in the study, nor between children and adults, and those with and without asthma.

All patients with initial mild reactions were non-adherent to SCIT at 3 and 5 years. Those with initial moderate and severe reactions had better adherence rates, but the difference was not statistically significant.

Among the patients included in the analysis, 16% discontinued treatment at the recommendation of their allergist and 77% self-directed. The leading reason for not continuing therapy was relocation to a non IFA-endemic area. Fear of shot reaction, inconvenience, and lack of healthcare insurance were also mentioned.

RUSH immunotherapy was associated with lower sustained adherence, but concurrent venom immunotherapy was associated with better adherence at 3 and 5 years.

“The findings suggest that even though studies have proven that IFA is safe, effective, and potentially lifesaving, a significant majority of patients fail to complete the prescribed duration of treatment,” Neaves said.

Neaves disclosed no relevant relationships with industry.