What is the most likely reason for Natasha’s nasal symptoms?
Specific IgE blood test results will indicate whether the patient is sensitised (has IgE antibodies) to specific allergens. Specific IgE values of ≥0.10 kUA/L indicate sensitisation,3 and the probability of allergy increases with increasing specific IgE antibody concentrations.4 Results should always be interpreted in conjunction with the clinical history and physical examination.1,5 When test results are concordant with the clinical history, a diagnosis of allergic rhinitis can be made.1
In Natasha’s case, the specific IgE test results show that she is polysensitised, with sensitisations to house dust mite (HDM), Timothy grass, silver birch, and Alternaria alternata. She has very high levels of HDM-specific IgE, but perhaps surprisingly, given her clinical history, her results indicate that she is not sensitised to cat dander. Therefore, it is likely that her asthma attack during the sleepover with her friend was due to HDM rather than the cat—a point which would have been very difficult to ascertain from her history alone.
Natasha’s sensitisation to seasonal allergens (Timothy grass, silver birch, and Alternaria alternata) may be the reason for her worsening nasal symptoms and breathlessness over the summer months, as her total allergen load will be increased compared with winter months.6
Interpreting these results in conjunction with Natasha’s clinical history and physical examination findings, allowed the GP to confirm a diagnosis of IgE-mediated allergy7—in this case, perennial allergic rhinitis (due to HDM) and seasonal allergic rhinitis (due to Timothy grass).
Management
HDMs are impossible to completely eradicate from a house by cleaning;8 however, Natasha could limit her exposure to HDM by using the following strategies:
- Put dust-proof covers on pillows, mattresses, and box springs. Remove and wash the covers frequently.8,9
- Minimise the number of stuffed animals kept in bedrooms or put them in plastic containers.8
- Remove carpets, drapes, and upholstered furniture (as much as possible).9
- Keep humidity to ≤45 percent.9
- Vacuum carpets twice every week.9
Natasha's peak nasal inspiratory flow is below the normal range determined for adult female patients (~115 mL/min), indicating nasal obstruction.10 Normal adult PEFR range is between 400 and 700 L/min.11 From her lung function tests, Natasha's low PEFR and FEV1 suggest intrapulmonary airflow obstruction,12 which, taken together with her clinical history, is indicative of asthma.13 Her FeNO is raised, but caution should be exercised when interpreting this result, as the presence of allergic rhinitis can elevate FeNO levels, even in the absence of overt, clinical asthma.1
Did you know?
- Up to 90 percent of allergic patients are polysensitised.14
- Allergic rhinitis confers a 3.5-fold risk for subsequent development of asthma,15 and is a marker of poor asthma control.16