Diagnostic testing for galactose-alpha-1,3-galactose, United States, 2010 to 2018

Background: Alpha-gal syndrome (AGS) is an emerging immunoglobulin E (IgE)-mediated allergy to galactose-alpha-1,3-galactose (alpha-gal). The geographic distribution and burden of AGS in the United States are unknown. Objective: To characterize alpha-gal IgE testing patterns and describe the trends and distribution from 2010 to 2018 in the United States. Methods: This retrospective analysis included all persons tested for alpha-gal IgE antibodies by Viracor-IBT Laboratories (Lee?s Summit, Missouri), the primary site of testing in the United States. Data included age and sex of person tested, specimen state of origin, collection date, and result value; persons with at least 1 positive test result (?0.1 kU/L) were compared with negatives. Proportions tested and with positive test results were calculated using the US Census population estimates. Results: Overall, 122,068 specimens from 105,674 persons were tested for alpha-gal IgE during July 1, 2010, to December 31, 2018. Nearly one-third (34,256, 32.4%) had at least 1 positive result. The number of persons receiving positive test results increased 6-fold from 1110 in 2011 to 7798 in 2018. Of those receiving positive test results, mean [SD] age was 46.9 (19.8) years; men were more likely to test positive than women (43.3% vs 26.0%). Arkansas, Virginia, Kentucky, Oklahoma, and Missouri had the highest number of persons who were tested and had a positive result per 100,000 population. Conclusion: More than 34,000 persons, most presumably symptomatic, have received positive test results for IgE antibodies to alpha-gal, suggesting AGS is an increasingly recognized public health problem. The geographic distribution of persons who tested positive is consistent with exposure to Amblyomma americanum ticks. Published by Elsevier Inc. on behalf of the American College of Allergy, Asthma & Immunology. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

This study characterized the testing patterns, trends, and distribution of alpha-gal IgE in the United States from 2010 to 2018, finding that over 34,000 persons were tested with approximately one-third showing positive results. Men were more likely to test positive than women, and states such as Arkansas and Virginia had higher numbers of individuals tested and with positive results.