Alpha-gal Syndrome: 42% of U.S. Clinicians Surveyed Had Never Heard of It

Alpha-gal syndrome (AGS) is an emerging allergy linked to tick bites. People with it react to galactose-alpha-1,3-galactose (alpha-gal), a sugar molecule found in most mammals other than primates — and so in red meat and other mammal products, including milk and dairy and some medicines. Reactions range from a rash or stomach upset to life-threatening anaphylaxis, and usually begin 2 hours or more after exposure. There is no treatment or cure.

In the United States the allergy is linked mainly to the bite of the lone star tick (Amblyomma americanum), and cases are most common in the South, Midwest and mid-Atlantic, where that tick lives. The number of people testing positive for alpha-gal antibodies rose from 13,371 in 2017 to 18,885 in 2021. Yet patients say most health care providers know little or nothing about AGS. A CDC survey set out to measure that.

The survey

In spring 2022, a nationwide web survey reached 1,500 providers who actively saw patients and had practiced for more than three years: 1,000 family physicians, general practitioners and internists, 250 pediatricians, and 250 nurse practitioners and physician assistants.

What providers knew

Among the 865 who had heard of AGS:

• 674 (78%) had not diagnosed a case in the previous year; 136 (16%) had diagnosed or managed one to five patients, and 55 (6%) more than five.
• 416 (48%) did not know the right diagnostic tests to order.
• Only 285 (33%) knew people get AGS from a tick bite; 272 (32%) said they did not know how it was acquired.
• 502 (58%) correctly identified what to counsel patients about: preventing tick bites, cutting out red meat, caution with new medicines and vaccines, and recognizing and managing anaphylaxis.
• Just 42 (5%) answered all three knowledge questions — cause, testing and counseling — correctly. Pediatricians did best (12.3%), then internists (4.2%), family practitioners (3.7%), physician assistants (2.6%) and nurse practitioners (0%). Region and years in practice made no significant difference.

About two in three wanted guidelines: 64% for diagnosis and 66% for management.

A worrying pattern

Strikingly, providers who reported diagnosing or managing more AGS patients scored lower on knowledge. The authors suggest some may be misdiagnosing AGS on symptoms or a test alone, and advising diet changes patients don’t need — while others miss or delay the diagnosis.

Diagnosis requires a careful history in a patient with compatible symptoms plus a blood test for alpha-gal–specific IgE antibodies (0.1 kU/L or more is positive). Delays are long: a 2015 study found only 21% of patients were diagnosed within the first year of symptoms, and the other 79% waited an average of 7.1 years. Patients may need repeated visits and referrals — a particular burden for those who struggle to get care or lack access to specialists such as allergists.

Why it matters

AGS is not nationally notifiable, so tracking depends on laboratory data. If providers don’t know to test, cases go uncounted and the true prevalence stays unknown. With positive tests and suspected cases rising and the lone star tick’s range expanding across North America, the authors call for better provider education to speed accurate diagnosis and improve care.

Limits: respondents came from a provider panel and may not represent all U.S. providers, and some may have read the answer options differently — for example, choosing “the cause is not yet known,” since the immunology of how tick bites trigger AGS is still being studied.

Sources

Based on Carpenter A, Drexler NA, McCormick DW, et al., "Health Care Provider Knowledge Regarding Alpha-gal Syndrome — United States, March–May 2022," MMWR Vol. 72, No. 30, CDC; a work of the United States government in the public domain. The source’s spelling of the tick’s genus, “Ambylomma,” is corrected to Amblyomma.