Investigations
1st investigations to order
allergy skin prick tests
Test
Should be carried out to exclude allergic rhinitis.[3][4]
Tests bound IgE direct response.
Most specific and sensitive.
Less effective if there is a history of dermatographism, history of severe eczema, or the patient is taking a histamine-blocker, ACE inhibitors, or tricyclic antidepressants.
May be used in the presence of high-dose corticosteroid use, despite possible attenuation of the skin testing responses.
NAR should exclude entopic rhinitis where patients have negative skin tests but localised specific IgE antibodies in nasal secretions.
Nasal provocation is the gold standard for confirming this diagnosis.[22]
Result
negative
serological specific IgE testing
Test
May be used to exclude allergic rhinitis if skin prick tests are not possible or if the results of skin prick testing are ambiguous.[3][4]
Enzyme-linked immunosorbent assay-based test has replaced the traditional radioallergosorbent technique.
More expensive than skin prick testing.
May give a false negative out of season because serum IgE has a 2.5-day half-life (checking specific IgE for spring tree pollen in the autumn or winter could result in lower levels of specific IgE).
May give a non-specific response if total IgE levels are very high.
NAR should exclude entopic rhinitis where patients have negative skin tests but localised specific IgE antibodies in nasal secretions.
Result
negative
Investigations to consider
nasal eosinophil smear
Test
Options include nasal swab or lavage or probe.
Must be performed off corticosteroids, and even extensive nasal saline irrigation or swimming can cause a false-negative result.
False negatives are common, but positive results are useful in identifying non-allergic rhinitis with eosinophilia syndrome.
Result
elevated
sinus computed tomography
Test
Used to rule out structural problems. Indications include unilateral symptoms, failure to respond to acute trial of decongestants, bloody rhinorrhoea, pain, or suggestion of mass on examination.
Result
normal
nasal endoscopy
Test
Most useful in evaluating vocal cords if there is hoarseness or throat swelling. Sinus computed tomography provides more extensive structural information and is therefore preferred for most purposes.
Result
normal
nasal provocation test
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