Tool stratifies reaction severity among patients with fish allergy
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Key takeaways:
- The food allergy severity score classifies reactions by the bodily systems that are involved.
- Tuna and cod were associated with the most severe reactions.
- Higher scores were associated with anaphylaxis.
The validated food allergy severity score was useful in classifying the severity of reactions among patients with allergies to various fish, according to a letter published in Annals of Allergy, Asthma & Immunology.
“Fish consumption is increasing worldwide, leading to more reported cases of food allergy reactions,” Helena Pires Pereira, MD, allergy and clinical immunology department, Coimbra University Hospital Center, told Healio.
However, data on how to accurately characterize the severity of these allergies is limited, especially pertaining to the diversity of fish species consumed, she continued.
“We aimed to use the [ordinal Food Allergy Severity Score (oFASS)], a clinical tool designed to categorize allergic reactions by severity, to better understand the specific factors influencing fish allergy reactions, particularly in a Portuguese population where fish is a dietary staple,” Pires Pereira said.
Study design, results
The retrospective study comprised 73 patients (median age, 14 years; 61.6% male) aged 2 to 79 years with an IgE-mediated fish allergy.
Atopic comorbidities, reported by 68.5% overall, included allergic rhinitis (57.5%), asthma (16.9%) and atopic dermatitis (27.4%). Also, 60.3% had a food allergy other than fish, of whom 56.8% reported a shellfish allergy.
Allergic reactions by species included tuna (31.5%), codfish (23.3%), hake (12.3%), salmon (12.3%), sardine (9.6%), and pilchard (5.5%), with single reactions to other fishes (5.5%).
Perciformes, or perch-like fish, accounted for 41.1% of reactions. Gadiformes, or cod-like fish, accounted for 35.6%.
Also, 68.5% of the patients ate cooked fish and 31.5% ate raw fish, and the authors noted that 65.22% of the reactions to tuna occurred after these patients ate it raw. Reactions occurred in dining establishments (61.6%) and at home (38.4%).
Among the 31 patients (42.5%) who were positive for parvalbumin (Gad c 1), 35.8% were triggered by tuna, 32.3% reached to codfish, 19.4% reacted to salmon and 12.9% reacted to other fish species. Half of the patients who were allergic to multiple fish species were positive for Gad c 1 as well.
The researchers assessed these reactions via three grades of 1-3 on the oFASS-3. Mild reactions (1) on this scale only involve the oral cavity. Moderate reactions (2) include one or more systems on a list encompassing the skin, nose, eyes, digestive system or uterus and may include the oral cavity. Severe reactions (3) include one or more of the systems on the moderate list in addition to one or more systems from a list including the larynx/bronchi, cardiovascular system and nervous system.
The cohort included 53.4% (n = 39; median age, 17 years; 53.8% male) with mild reactions, 26% (n = 19; median age, 8.5 years; 73.7% male) with moderate reactions and 20.5% (n = 15; median age, 16; 66.7% male) with severe reactions.
The median reaction was mild (1; interquartile range, 1-2). There were no fatal reactions.
The most common triggers in the severe group were tuna (n = 7; 46.7%) and cod (n = 4; 26.7%), which also were associated with milder reactions, the researchers said.
“One of the most surprising findings was that tuna, despite being perceived as lower-risk due to its lower parvalbumin levels, was the most frequently implicated fish in severe allergic reactions,” Pires Pereira said.
These findings run counter to previous research indicating that cod and other fish species with higher parvalbumin levels usually are more allergenic, she continued, in addition to contradicting the common belief that tuna is less allergenic.
“This may be related to different preparation methods,” Pires Pereira said. “Raw tuna was a significant trigger in our population, and raw fish typically contains higher levels of allergenic proteins like parvalbumin compared to cooked fish.”
The correlation between shellfish co-allergy and more severe fish allergy reactions also was significant and may indicate a pan-allergen effect, Pires Pereira continued, especially with proteins such as tropomyosin.
“The strong association between shellfish co-allergy and reaction severity underscores the importance of identifying cross-reactive allergens, such as tropomyosin, which could affect patients allergic to both fish and shellfish,” Pires Pereira said.
Additionally, the researchers noted significant correlations between oFASS-3 and allergy to more than one fish regardless of its subtype (r = 0.306; P = .009) and co-allergy to shellfish (r = 0.32; P = .02). There was a strong correlation between anaphylaxis due to fish allergy and higher oFASS scores as well (r = 0.756; P = < .001), the researchers continued.
Conclusions, next steps
Based on these findings, the researchers said that oFASS scores could be valuable in characterizing reaction severity, adding that they are easy to apply and have strong correlations with fish anaphylaxis and other variables.
“These findings highlight the importance of comprehensive fish allergy assessment, including molecular testing,” Pires Pereira added.
Clinicians also should be aware that patients can still have severe reactions to tuna and other fish species that are seen as less allergenic, she added.
“The oFASS score can help stratify patients by reaction severity, allowing for tailored management strategies,” Pires Pereira said.
The researchers also called for larger studies that involve more detailed characterizations of molecular fish allergen patterns including enolase and aldolase to provide more insights into fish allergy.
“Expanding the scope to different populations would help validate our findings and improve global understanding of fish allergy patterns,” Pires Pereira said. “Additionally, further investigation into the role of tropomyosin and other pan-allergens in cross-reactivity could aid in better predicting reaction severity.”
For more information:
Helena Pires Pereira, MD, can be reached at helenapereira089@gmail.com.
Perspective
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Fish is a protein source that can be invaluable to healthy eating. When compared with other animal sources of protein such as beef, pork, or poultry, it tends to be the most lean. This means it has a lower content of saturated fats, which are inflammatory fats that increase one’s risk for heart disease. Due to the lower fat content, fish also tends to be higher in protein by weight when compared with other animal products.
Additionally, fatty fish contains omega-3 fats, an anti-inflammatory unsaturated fat with a myriad of health benefits that include brain health, heart health and even improved athletic performance. Omega-3 also happens to be an essential nutrient, meaning the body cannot make it on its own. We must obtain it from food, and fish are the richest dietary sources of omega-3.
Given that fatty fish twice a week is how the USDA recommends Americans obtain their omega-3, an allergy to fish can present a problem. Although there are some plant sources of omega-3 such as chia seeds, flaxseeds and walnuts, they aren’t nearly as well absorbed by the body as the omega-3 found in fish. Furthermore, you can supplement with omega-3, but the most common supplement forms are fish and krill oil, which are not safe to take if you have a fish allergy.
The severity of fish allergies identified in the study highlights the need for doctors to explain to patients what nutrients they are missing out on by excluding fish from their diet and what foods they should consume to obtain those nutrients.
Allergists would benefit from collaborating with a registered dietitian to identify a dietary pattern that can provide proper nutrition while accounting for the elimination of fish from the diet. Including the plant sources listed along with recommending omega-3 supplements that are fish-free (such as algae-based omega-3 supplements), but still rich in DHA, could be critical to building a well-rounded eating plan.
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