Y Bajaj, U Raghavan, S Mortimore
allergy, benefits, skin tests
Y Bajaj, U Raghavan, S Mortimore. Benefits Of Skin Prick Tests For Allergic Rhinitis. The Internet Journal of Otorhinolaryngology. 2006 Volume 6 Number 1.
1. The patients view about the benefits of allergy skin prick test.
2. Did this test make any difference in the management of these patients?
Allergic rhinitis is a health problem and a major concern among the UK population. It affects 10 – 20% of the general population1. Up to a third of teenagers are affected by allergic rhinitis with or without other allergic diseases2. The prevalence of allergic rhinitis is increasing in European countries3, 4. Allergic rhinitis can be perennial caused by dust mites and animal dander or seasonal when it is caused by a variety of pollen. The principle features of allergic rhinitis are nasal itching, sneezing, watery rhinnorhea, nasal obstruction and sometimes with additional symptoms such as headache, anosmia or hyposmia and itching and redness of eyes1. Many conditions such as nonallergic rhinitis with eosinophilia, rhinitis medicamentosa, nasal polyposis, chronic sinusitis, Wegner's granulamatosis etc can mimic allergic rhinitis. Some of these conditions may coexist. The investigation for suspected allergic disease includes a detailed accurate clinical history both personal and familial, prior treatment and benefits from these treatments, presence of other allergic disorders, a physical examination and the use of in vivo or in vitro tests to determine the patient's sensitivity to the provoking allergen. Skin tests properly performed and properly interpreted are the most useful diagnostic tests to document specific IgE reactivity5. Pumihurun6 concluded that the skin prick test can be used as a screening method for patients with allergic rhinitis, while the specific IgE detection can be used as an alternative for diagnosis of patients who are susceptible to the intradermal test or for those who are severely susceptible to allergic rhinitis such that medication can not be withdrawn for the intradermal test.
In the UK almost all the patients with intermittent or persistent nasal symptoms are first examined and treated by primary care physicians. Depending on their symptoms and examination findings these patients are treated with oral antihistamines and/or intranasal steroids. Facilities to do skin prick test on all these patients are not available. If the patient does not get the expected relief from their symptoms these patients are referred to the rhinologists.
The aim of this study was to investigate the patient's point of view about the usefulness of skin prick tests performed in the rhinology clinic and the difference it made in the management of these patients with allergic rhinitis.
Materials & Methods
Retrospective analysis of 99 patients who had positive skin prick tests over 12 months from Jan 2000 to Dec 2000 at Derby Royal Infirmary was done. Skin prick test was done for house dust mite, grass, cat, dog & any other specific (guinea pig, horse etc.) suspected agents. Following skin tests these patients were given information leaflets about allergic rhinitis and allergen avoidance.
Questionnaires were sent to all the patients with positive skin tests.
Skin prick test produced a positive result in 99 patients. Of these 43(43.4%) were males and 56(56.6%) females. The questionnaire was returned by 59 patients (59.6%). Majority (93.2%, 55/59) of these patients were aware about the purpose of skin test. Among the 59 patients 37 were not aware of any known allergy and the remaining 22 knew about allergic reaction to grass, dust mite and pets.
Of the patients with positive skin test (99), 24 did not receive any previous anti allergy treatment, 42 received single nasal steroid, 17 had tried many nasal steroids. Eight patients tried an antihistamine alone. Another 8 had tried both antihistamines and nasal steroids.
The effectiveness of the treatment received from GP's was assessed by the 59 patients who returned the questionnaire. Of these, 20 patients used nasal spray with 9 finding it useful and 11 not enjoying any relief of symptom. Of the remaining patients, 8 tried antihistamines alone and 5 of them experiencing benefit. Another 8 used both antihistamines and nasal steroids, with 4 finding them effective.
The common symptoms in this group were nasal obstruction 54(53.5%), rhinorrhoea 28(19.2%), sneezing 28(19.2%), post nasal drip 19(11.1%) and anosmia in 2(2.02%).
Skin test results showed that most common allergen was house dust mite (75.7%; 75/99) followed by grass pollen (52.5%; 52/99), dog (23.2%; 23/99) and cat (27.3%; 27/99).
Among the 59 patients who responded to the questionnaire 6/8 patients accepted getting benefit from the information leaflet alone. Benefit was achieved by both information leaflet and changes in medication in 16/23 patients. With the information leaflet and continuing on the same treatment as pre-skin test, 13/28 patients benefited. Overall 35/59 (59.32%) patients benefited from the skin tests with 95% confidence interval of 46.78%-71.82%.
P value for benefit from skin test in this study was <0.005 (2 sided p value: 0.002
Allergic rhinitis is common among UK population. The usual diagnostic criteria for allergic rhinitis include a correlation between clinical outcomes and the exposure to allergen, physical examination and a positive diagnostic test 6. In vitro and in vivo tests are available for identifying the allergen. Sin et al7 has mentioned that the skin test is the diagnostic method of choice to evaluate IgE mediated sensitivity and this test has shown correlation with symptoms and RAST. Pumhirum et al6 found more than 85% sensitivity and over 90% specificity when skin prick tests were done for mites. Skin test is also recommended by the consensus statement1. However Palacios et al8 states there is lack of correlation between clinical diagnosis and skin tests. Hordle et al9 believes that the routine use of skin prick test is not a practicable proposition for large number of allergens.
In our study 35% of the patient with allergic rhinitis symptoms developed negative reaction when skin prick test was done using common allergens. This is against the reported sensitivity and specificity by Pumhirum et al6. In the UK the general practitioner initially treats almost all patients with upper airway allergy. However 25% of our patients with positive skin tests did not have any previous anti allergic treatment. The remaining 75% were treated by antihistamines or nasal steroids or both. Of the 59 patients who answered the questionnaire 23 did not receive previous treatment. About 50% of these patients who received treatment had relief of symptoms.
Among those patients who replied, 10.2% benefited from the skin prick test and the allergen avoidance advice. Another 49.2% benefited by the allergen avoidance with the help of anti allergy treatment. As some of these patients were already using anti allergy treatment the symptom control they have achieved may be because of the allergen avoidance which they were made aware after the skin prick test. The symptoms were not controlled by allergen avoidance and medication after skin prick test in 40.6% of patients. Even though the patients assured us that they followed all the advice given in allergen avoidance information leaflet there is no way to confirm these and we accept that at least part of these failure may be due to lack of compliance. Also there is a possibility of bias as only 60% patients replied to the questionnaire. Of the patients who responded to the questionnaire 37% were already aware of their allergy which was confirmed by the test. No additional benefit was achieved by performing a skin prick test on these patients. Of the 59 patients who responded to the questionnaire, 59.32% felt the benefit from skin prick tests.
The most common allergen in our study was house dust mite. This study shows that though the skin prick test is a reliable test to diagnose allergy, it may benefit about 60% patients who test positive. The majority of the patients are already on various treatments. A high percentage of patients are reliably aware of their allergies and performing skin prick test in these patients did not provide additional benefits. Those patients not aware of their allergies and not benefiting from treatment, may be helped by a skin prick test. The patients should be warned of these rates in the initial consultations to avoid giving them false hopes of cure.
Mr Y Bajaj,
2, Tall Trees