Prevalence of Allergic Disorders and Allergen Sensitization Patterns in a Tertiary Care Corporate Hospital in North India

INTRODUCTION

Allergic disorders are highly prevalent across all age-groups and settings globally. The Indian subcontinent is home to several forms of allergic disorders owing to the wide range and distribution of flora and fauna in the country. Estimates state that more than 25% of the Indian population is sensitized to different forms of allergens.¹ Major sources of allergen in India are pollen grains, fungal spores, animal epithelia, food items, insects, and dust mites.^2–4 A multi-centric population-based study (IN-SEARCH) in India reported that the prevalence of asthma, chronic bronchitis, and allergic rhinitis were 2.05, 3.5, and 3.3%, respectively.⁵ Data on the pediatric population revealed that 3.3% of children aged 6–7 years and 5.6% of children aged 13–14 years were diagnosed with allergic rhino-conjunctivitis. It has been observed that 20–30% of the population suffers from allergic rhinitis and 15% of them developed atopic asthma.⁶ In addition to asthma, the other forms of allergy, such as atopic rhinitis, anaphylaxis, drug, food and insect allergy, hypersensitive pneumonitis, atopic dermatitis, contact dermatitis, eczema, urticaria, angioedema, rhino-conjunctivitis, serum sickness, vasculitis, and granulomatous reactions were also on a rising trend in terms of prevalence as well as severity in India.⁷

The specific diagnosis of immunoglobulin E (IgE) mediated allergy is usually based on the correlation between the clinical history and signs and symptoms and is endorsed by diagnostic tests. Skin prick tests are the gold standard for demonstrating an IgE-mediated mechanism behind the allergic symptoms but their efficacy totally depends on the use of standardized skin prick test solutions. Data from hospital-based studies has shown a sharp increase in the prevalence of IgE-mediated allergic disorders in the past few years.⁸ Prosopis juliflora among pollen allergens and Alternaria alternata among fungal allergens were common sensitizers reported in allergic patients with skin positivity of 34.7 and 17.7%, respectively.⁸ In Western countries, recombinant allergen-based advanced diagnostic tools like Immuno-CAP and allergen microarray have revolutionized molecular diagnosis, which are sparsely available facilities in the Indian settings.^9,10 Accurate diagnosis and therapeutic intervention of allergy is difficult in India due to dependence on skin prick test using crude allergen extracts.^11,12 Therapeutic measures viz immunotherapy with hypoallergenic variants, allergen-derived peptides/fragments, and genetically engineered allergen derivatives are widely used in the Western world while sparsely available in India.¹³ Economic constraints, lack of prioritization, and legal requirements for company licensing are primary deterrents to the availability of such diagnostic and therapeutic services in India.

It is necessary to understand the spectrum of key allergens and their determinants so as to strengthen the evidence base for prioritizing the availability of diagnostic and therapeutic interventions for this set of disorders in the country. The present study aims to understand the prevalence, clinical presentation, and determinants of allergic disorders at a tertiary care hospital in North India. Additionally, we strive to study the spectrum of allergens contributing to the broad dimension of IgE-mediated disorders and the sensitization pattern in Northern India.

MATERIALS AND METHODS

RESULTS

DISCUSSION

The most common allergy diagnoses in the present study were allergic rhinitis (82.4%), atopic dermatitis (49.6%), and allergic asthma (46.9%). Allergic rhinitis was significantly more prevalent in males (86.8%) while other disorders were in similar proportions across the genders. Majority of the patients had ≥3 allergic disorders at a time (68.4%). Nearly half of the patients had perennial allergy with seasonal exacerbations (49.6%) and most allergies occurred indoors (59.0%). The most common triggers for allergic symptoms were consumption of a particular food item [102 (39.8%)] and dust or dusty atmosphere [80 (31.3%)]. The most common allergens identified were mites followed by pollens and molds. Sensitization, was most commonly observed with D. farinae (67.6%) and D. pteronyssinus (68.0) which were also the most commonly implicated allergens across Punjab, Haryana, and Himachal Pradesh. Patients residing outside were also most commonly sensitized to D. farinae (81.8%) and D. pteronyssinus (72.7%). The number of allergens causing sensitization increased with increasing age. The major allergens were D. farinae [23 (50.0%)] and D. pteronyssinus [23 (50.0%)] across all age-groups.

There might be a possibility of selection bias in the study as the patients were recruited from the allergic clinic of a tertiary hospital. However, we had a representation from four major northern states/union territories of India. The response rate in the study was high as only 4.1% of participants withdrew from the study. We used standardized solutions for skin prick test and the determination of allergens, thereby reducing the possibility of measurement bias in the study. We cannot completely rule out the possibility of recall bias as the participants may have forgotten the possible triggers, given the fact that allergies might have been triggered due to multiple exposures. Overall, the results are likely to be reliable and representative of the target population given the relatively low risk of bias.

Respiratory diseases represent 25% of all outpatient visits to a general physician and about 80% of patients with recurrent presentations are later diagnosed allergic.¹⁵ A study by Yoo et al. reported that the common presentations of allergic disorders are eczema, rhinitis, urticaria, atopic dermatitis, conjunctivitis, angioedema, asthma, anaphylaxis, affecting >40% of the population.¹⁶ Our findings are in line with these findings showing allergic rhinitis (82.4%), atopic dermatitis (49.6%), and allergic asthma (46.9%) as the most common presentations. Simpson et al. reported that co-existence of multiple allergic disorders has increased with time.¹⁷ Similarly, a study by Kumar et al. in 2012, showed polysensitization to more than two aeroallergens.¹⁸ Our findings also report sensitization to ≥3 allergens at a time in most patients. Previous studies done in different settings across countries have reported house dust mite as the most frequently reacting allergen in skin prick test.^19–21 Also, in our study, a majority of the patients were sensitized to D. farinae and D. pteronyssinus dust mites and the pattern was similar across all states. There was predominant sensitization to dust mite in all geographical areas with certain kinds of allergens being more common than others in some states. This points toward the geoclimatic and vegetation variation across these agricultural states. This changing environment has changed the profile of allergens as well as intensity of exposure in the country. It was observed that elevated temperatures and higher CO₂ levels resulted in an increase in the pollination cycle of weeds, thereby increasing the pollen load in the air.²² In a study done at Vallabhbhai Patel Chest Institute in New Delhi, the age-group most commonly affected by allergic disorders was 20–30 years. In contrast, our study reported 6–18 years as the most common age-group affected by allergic disorders. This may be due to the differences in the study population enrolled as the present study was done in a pediatric allergy clinic while the other study was done in an adult allergy clinic. We also found that the number of allergens causing sensitization increased with an increase in age possibly due to body’s susceptibility and increase in exposure to environmental allergens. Another reason could be increasing sensitizations starting from the early age-group due to lifestyle, dietary changes, and increasing chemical exposure.

Our study has certain limitations. The patients who had access to the hospital in terms of location and socioeconomic factors only were recruited, thereby reducing the generalizability of the findings. Serum specific IgE levels could not be tested in all patients due to financial constraints. Additionally, due to non-availability of molecular tests, we could not characterize the allergens in detail.

It has been found that low levels of sanitation, rapid urbanization, and deforestation are important factors contributing to the allergen distributions in the ambient environment.²³ Allergic disorders not only lead to poor quality of life but also pose a significant socioeconomic burden. Despite the availability of data on the high prevalence of allergic disorders in India and awareness regarding the diversity of allergens across states, the country still lacks well-equipped allergy centers. It is important to make advanced molecular diagnostics for allergies widely available so as to describe allergen characteristics and sensitization patterns more accurately. For designing successful therapeutic interventions, the identification of the specific offending allergen in a particular patient is the first step. This can be extremely difficult in India, given the cross-reactivity between allergens and diverse soil and environmental conditions that affect the protein content as well as the antigenicity of the allergens. Apart from diagnostics, the poor availability of therapeutic interventions in the Indian sub-continent is also an important issue. Modified allergen immunotherapy has been widely used in Western countries for the past two decades.^24–27 It is the process of causing immunomodulation in IgE-mediated diseases and is considered the only effective therapy against allergic diseases so far. There are sufficient numbers of clinical trials worldwide to prove its effectiveness and safety. In India, however, this therapy is still under development. Research on these diagnostic and therapeutic interventions needs to be prioritized in India. It is necessary to promote the availability of these interventions on a large scale, to combat allergic disorders in a more timely and efficient manner.

CONCLUSION

The burden of allergic disorders is high in the northern states of India with variation across states and age-groups given the different types of allergens. Methods for early identification are warranted to plan preventive and curative interventions and to potentially reduce the burden of allergic disorders in the country.

ACKNOWLEDGMENT

The author dedicate this study to his teacher and late professor Dr (MAJ) K Nagaraju.

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