Diagnostic evaluation of allergic rhinitis.

4.5 Diagnostic evaluation of allergic rhinitis.

allergic rhinitis are allergen-specific IgE levels and skin prick tests (SPTs). The clinical history should guide the clinician to test for the most relevant panel of allergens. It is important to note that a positive RAST or SPT, in the absence of a clear history, does not support the diagnosis of allergic rhinitis. Nasal biopsy and nasal lavage are research procedures and are rarely used in clinical practice (4.7, 4.8).

Allergic rhinitis can be classified as seasonal, perennial, or episodic (Table 4.1). Seasonal allergic rhinitis (SAR) is defined as: symptoms occurring during exposure to seasonal allergens, i.e. pollens of grasses, trees, and weeds (4.9, 4.10). Perennial allergic rhinitis (PAR) is defined as: nasal symptoms for more than 2 hours a day, for more than 9 months of the year. This happens when the patient is allergic to house dust mites, indoor moulds, animal danders, and cockroaches, or when patients are allergic to multiple seasonal allergens (4.11). Episodic allergic rhinitis refers to symptoms on exposure to allergens that are not normally in their environment, i.e. cat-allergic patients developing symptoms upon entering a house where there are cats. The severity of allergic rhinitis should also be assessed in accordance with recent guidelines (4.12).

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4.6 Top panel: skin prick test (SPT) should be considered to elucidate the specific cause. Bottom panel: investigations are used in special situations to rule out other associated conditions. (CT, computed tomography; RAST, radio allergen sorbent test.)

4.7 A nasal mucosal biopsy is usually used for research purposes to study the pathophysiological mechanisms of allergic rhinitis and the effects of treatment on the nasal mucosa.

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4.8 Nasal lavage is useful in evaluating the cellular population in allergic rhinitis. The anterior nares are lavaged by refluxing buffered saline, warmed to 37°C, with a syringe catheter apparatus. Nasal cytological examination is useful for the diagnosis of non-allergic rhinitis with eosinophilia syndrome (NARES). Intracellular bacteria and polymorphonuclear leukocytes are suggestive of an infectious process.

4.9 Pollen is a fine powder consisting of microgametophytes (pollen grains), which carry the male gametes of higher plants. Each pollen grain

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those of anemophilous (literally ‘wind loving’) plants, which produce very lightweight pollen grains in great quantities for wind dispersal, and subsequently come into contact with human nasal passages through breathing. Anemophilous plants generally have inconspicuous flowers.

4.10 Ragweed, a yellow flowering weed, is a member of the aster family that often flourishes in disturbed vacant soils which cannot support other vegetation. It flourishes during dry, hot spells which promote growth and pollen formation. If these conditions continue through late summer, then pollen dispersal is very high. The only deterrent to making it difficult for the plant to release its pollen is relative humidity that exceeds 70%. One ragweed plant is capable of producing over a billion grains of pollen per season. There are some cross-reactivities exhibited by ragweed-allergic subjects. The cross- reactive allergens linked to ragweed

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Avoidance of these foods is usually recommended to reduce compounding symptoms. A cross-reaction to ragweed pollen may cause oral allergy syndrome, which is itching or swelling of the lips, tongue, throat, or roof of the mouth.

Table 4.1 Classification and differential

diagnosis of allergic rhinitis

Allergic rhinitis Seasonal, perennial, episodic Non-allergic rhinitis Vasomotor rhinitis—clear rhinorrhea, nasal congestion without exposure to

allergens Cold air induced NARES—usually seen in adults, negative test for allergens and eosinophilia

on nasal smears Infectious rhinitis

Bacterial, fungal, and viral Drug-induced rhinitis Reserpine, OCP, rhinitis medicamentosa, beta blockers, hydralazine Granulomatous

Wegener’s granulomatosis, sarcoidosis rhinitis

Mechanical Foreign body, deviated septum, adenoids obstruction

Tumours Benign, malignant NARES, non-allergic rhinitis with eosinophilia; OCP, oral contraceptive pill