HOUSTON (FRONTLINE MEDICAL NEWS)For rituximab patients undergoing desensitization, mast cell degranulation is a more effective predictor of hypersensitive reactions (HSR) than are the traditionally employed skin tests, according to a study presented at the annual meeting of the American Academy of Allergy, Asthma, and Immunology.

“In this particular study, we were interested in investigating the roles of immunoglobulin E (IgE) in the mast cells in rituximab hypersensitivity,” said Dr. Johnson T. Wong of Massachusetts General Hospital, Boston, who presented the findings during a session dedicated to “Novel Insights in Drug Allergy.”

The study comprised 25 patients with persistent or severe rituximab sensitivity (RITS) who were treated at Massachusetts General between 2008 and 2013. Dr. Wong and his coinvestigators performed skin testing on 18 subjects, of which 7 (39%) reacted positively at least once during the course of testing.

HSR reactions occurred at similar rates in subjects who reacted positively and negatively to skin testing. Tryptase levels were taken in 18 subjects (72%), during 67% of the HSR desensitizations and 21% of the asymptomatic desensitizations.

Overall, elevated levels were noted in 21% of the HSR desensitizations.

The elevated tryptase levels in patients experiencing HSR indicates that mast cell degranulation is likely a major contributing factor in causing HSR, with cytokine release and tumor lysis also playing an important role, Dr. Wong said. Mast cell degranulations also points to an association with IgE mechanisms as a reliable indicator of HSR likelihood.

Dr. Wong and his coauthors concluded via tryptase level testing that asymptomatic mast cell degranulation happened very rarely, as only 1 out of 27 assessments (3%) indicated that result. One patient was excluded from the HSR desensitization cohort’s results because of probable mast cell activation syndrome, which caused abnormally elevated tryptase levels throughout the study period.

“In both positive and negative skin test patients, our desensitization protocol was able to reduce the reaction rate to less than 30%, so around 70% of patients had no reaction at all during desensitization,” said Dr. Wong, adding that nearly all desensitizations were completed successfully.

Dr. Wong had no disclosures.


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