BACKGROUND: The mean wheal diameter >/= 3 mm is the usual criterion for positive skin prick test (SPT) reaction to dust mites. The study assessed the accuracy of this SPT criterion with respect to specific IgE values of above 0.35 kUA/l (+ sIgE). METHODS: Specific IgE (ImmunoCAP, Pharmacia AB Diagnostics, Uppsala, Sweden) and standard SPT to Dermatophagoides pteronyssinus (DP) and farinae (DF), Lepidoglyphus destructor (LD) and Tyrophagus putrescentiae (TP) (ALK, Hørsholm, Denmark) were performed in a random sample of 457 subjects, of whom 273 men (mean age 35.3 +/- 11.0 years) and 184 women (mean age 37.9 +/- 9.5 years). Statistical analysis was performed using the chi-square test, regression analysis and discriminant analysis. RESULTS: When the mean wheal diameter of >/= 3 mm was considered positive (+ SPT), the correlation between + SPT and + sIgE was 0.47 for DP (P
INTRODUCTION: The aim of this study was to compare the allergy test with the skin prick test and the specific IgE by Phadiatop test to a purely clinical allergy diagnosis by an allergy specialist in adult patients previously tested in general practice. MATERIALS AND METHODS: A total of 103 patients suspected of having asthma and/or rhinitis were re-evaluated with a clinical diagnosis and the two allergy tests. Both the patient and the individual general practitioner were asked about existing allergy diagnosis. RESULTS: The two test systems showed large differences in a semiquantitative linear system with an explained variation (r2) of only 8%. In comparison to a purely clinical diagnosis, they were diagnostically equal with both tests, with an additional 15% positive reactions of which 25% were judged clinically active. Both tests resulted in about 33% false-positive tests classified as clinically inactive. In the case of a positive Phadiatop test and clinically active allergy, both the patient and the general practitioner reported identical specialist diagnoses in about 75% of cases, while in 20-50% of the cases an identical diagnosis was reported when the clinical diagnosis was qualitatively different from the result of Phadiatop. CONCLUSION: The results of the two test systems often differ, and they both detect extra positive tests, in which case they should be used in a serial manner. Both tests often result in a false-positive diagnosis, and identification of clinically relevant positive tests often requires an experienced medical evaluation.
The content of major allergens in biologically standardized allergenic preparations of birch, mite (Der p), cat, Alternaria (Alt a) and ragweed (Amb e) was determined. It was found fairly constant between species, i.e. varied within a factor of 2, with the exception of Alt a 1 in Alternaria alternata extract. This variation is allowed by authorities between different batches prepared from the same species of allergen. The method for biological standardization (BS) prescribed in the Nordic Guidelines has, for common inhalant allergens, been shown to give reproducible results between regions of Europe. However, it is difficult to define patients suitable for BS of most food allergens as well as less common inhalant allergens. Therefore we propose that, in the future, BS is replaced by determination of well-established major allergens and that 1 ng of major allergen is given the value of 1 Biological Unit.
Biological standardization (BS) aims at equilibration of the activity of allergen preparations from different types of allergen source materials. The biological unit (BU), proposed in the Nordic guidelines for 20 patients, has been found reproducible among different countries in Europe, but to be relatively imprecise, with a 95% confidence interval of about one power of 10. A more precise estimate of the biological activity of allergens or difference in sensitivity between populations would be of value. We used Ch, i.e. the concentration of allergen eliciting a wheal of the same size as histamine in the individual patient, estimated by regression line analysis. The Ch of 36 patients included in a BS trial was used. One of the 36 Ch-values was drawn randomly, and then sent back to the sample. This procedure was repeated 10, 20, 30, 40 and 60 times to create "samples" of different sizes. Ten samples of each size were produced. With 60 "individuals", the 95% confidence interval of the sample and the confidence interval of the medians were reduced to less than a factor of 2, i.e. to 74 to 128% of the median of the medians.
The aim of our study was to assess whether general practitioners and their staff (practices) who had attended a short CME course with technical instruction in the skin prick test could diagnose and treat unselected patients with allergic rhinoconjunctivitis at the same quality level as the allergy outpatient clinic.
We performed a multicentre study with the participation of 38 general practices and the Allergy Centre at Odense University Hospital (OUH). After a two-day course for the general practitioner and his practice staff, every practice performed a skin prick test on 10 consecutive adult patients with symptoms of allergic rhinoconjunctivitis during the spring and summer. A standardised questionnaire was also filled in and sent to the Allergy Centre, where the patient subsequently had another skin prick test carried out. The results of the tests were determined in duplicate and then compared.
No significant differences in the quality of the skin prick test for 10 allergens or histamine control were found between the general practice and the Allergy Centre. Discordant results were found in 9%, i.e., a positive result either at the practice or the Allergy Centre, but not at both.
After a training course, general practitioners and their staff are fully able to perform and validate skin prick tests for inhalation allergens.
Comment In: Ugeskr Laeger. 2007 Feb 19;169(8):734; author reply 73417338041
Eleven general practitioners performed skin prick tests for specific pollen allergy (birch, timothy and mugwort) in 109 patients. One to two weeks later all 109 patients were skin prick tested again by one and the same very experienced nurse in a specialised allergy clinic. The results of the allergy-nurse were defined as "the real values". When the two sets of skin prick test were compared, 272 (83%) of all 327 skin pricks were of same size and class compared with the positive histamine-references. Forty-eight skin pricks (14%) were marginally different. Three skin prick tests (1%) were falsely positive and four (1%) were falsely negative. The study shows that general practitioners can after a short time of education and training perform and classify skin prick testing with great performance and at the same level as specialised allergy clinics. Skin prick test is a good supplement to clinical examination in general practice in the diagnosis of specific allergy in rhinoconjunctivitis and asthma bronchiale and in making suitable referrals to specialised allergy clinics.