Nasal provocation test: how to maximize its clinical use?

Asian Pac J Allergy Immunol 2010;28:225-31criteria and techniques are adapted from EuropeanResearch Centers 7 .This article summarized the usefulness ofNPT, its indication and contraindication, dosageand instillation techniques for allergens andevaluation of outcome in the hope that if we canstandardize the procedure and make it easier toperform, NPT will be applied more in clinicalpractice. In addition normal values among Asianethnics are presented for appropriate interpretationof the test.Application of NPT and its importanceSkin Prick testing (SPT) is a standard testingfor allergy diagnosis. Patients with larger whealsizes from SPT are the ones with higher clinicalcorrelation than those with smaller wheal sizes.Some patients with negative SPTs but withpositive intradermal tests (IDT) do not react toallergen challenge. However, this has recentlybeen questioned by reports from Bodtger in 2006and Scadding in 2007. These authors reported thatpatients with ab definate allergic history but withnegative skin tests could later become developboth positive skin test and NPT results 8,9 . Suchpatients with convincing allergic history couldmake it difficult for clinicians to make a correctdiagnosis during their first encounter with thepatient. When there is doubt regarding thediagnosis of nasal allergy, NPT could be a usefulprocedure for such patients 10,11 . Moreover, thosewith multiple sensitivities, i.e., those who react toseveral allergens by skin testings, should becandidates for NPT in order to identify the culpritallergens. Thus, such patients could be improvedthrough environmental control measures and thephysician could select appropriate allergens forallergen immunotherapy.To date, the indications of NPT are:1. To confirm the diagnosis of allergicrhinitis in patients with negative allergy skin testsor without serum specific IgE.2. To confirm the clinical relevance of aspecific airborn allergen in patients with multiplesensitivities, as determined by skin testings 12 .3. To confirm nasal reactivity to specificallergen before initiating immunotherapy 13 .4. To assess the hyper-reactive state of nonallergicrhinitis, using capsaicin- orlipopolysaccharide (LPS)- challenge 14 .5. To confirm the role of a specific allergenin patients with bronchial asthma in whichbronchial provocation test could not be safelyperformed 7 .6. To confirm the role of a specificoccupational agent 15,16 .7. To study patho-physiology of allergicand non allergic reactions.8. For allergy research such as theidentification of new allergens or in the processof evaluating new treatments for allergicconditions.Nevertheless, NPT is still not used as often as itcould be in clinical practice.NPT can be carried out safely with only a fewminor side effects. In order to avoid side effects,NPT should not be performed during anexacerbation of the allergic condition or inpatients with a history of severe systemicreactions (anaphylactic shock) to the particularallergen of interest.To minimize false positive results, NPT shouldbe avoided during an acute episode of rhinitissince the increase vascular permeability and nasalhyper-reactivity could alter the results 17 .To minimize false negative results, certainmedications should be discontinued prior to NPT.These are listed in Table 1.Principle of NPTAn allergen extract or other provocative agents isinstilled intranasally and the intensity of nasalsymptoms such as itching, sneezing, rhinorrheaand nasal obstruction occurred are recorded.Distant symptoms, such as ocular and bronchial,can be observed as well. The most importantoutcome parameter is nasal obstruction which canbe assessed by various methods such as peaknasal inspiratory flow (PNIF), rhinomanometry(RMM) or acoustic rhinometry (ARM) 19,20 .Table 1. Medications should be stoppedbefore nasal provocation test.MedicationsDuration to stop before nasalprovocation testOral antihistamine3 daysIntranasal corticosteroid 1 week 7 to 6 weeks 18Oral corticosteroid (greater than2 weeks10 mg/day)Topical nasal decongestant1 dayAntihypertensive (ACE inhibitors)3 weeks226Downloaded from http://apjai.digitaljournals.org. For personal use only. No other uses without permission.