Prevalence Of Skin Test Positivity Research Articles

Prevalence of allergic sensitization to Russian thistle in Kingston and the South-eastern Ontario catchment area; a retrospective chart review

Background Russian thistle has only recently been identified as a potentially clinically important allergen. In the third phase of the National Health and Nutrition Examination Surveys conducted in the USA (1988 to1994) over 15% of tested individuals had positive skin-test responses to this extract. The rate of skin test positivity to Russian thistle in Canada is unknown. Objective To determine the prevalence of skin test positivity to Russian Thistle in patients from Kingston and the Southeastern Ontario catchment area, and the possible clinical significance of the same. Methods A retrospective chart review was performed to document the rate of sensitization amongst tested patients to Russian thistle extract (Hollister-Steir). Only patients with appropriate histamine responses were included. We collected demographic data in addition to the presence/ absence of relevant clinical symptoms. Results Of 410 charts reviewed, 170 underwent skin testing to Russian thistle. Of these, 17(10%) were positive. Of the test-positive cohort, 47% (8/17) had symptoms that correlated seasonally with the predominant Russian thistle pollen season (August-October). The mean age of skin-test positive individuals was 35.2 years. 82% and 52.9% of these had concomitant positive skin tests to ragweed and birch, respectively, allergens with known cross-reactivity. Conclusions This preliminary evaluation suggests that the prevalence of skin test positivity to Russian thistle in the studied area is approximately 10%, with about half of these individuals reporting correlative seasonal symptoms. Including Russian thistle in routine skin testing panel may better establish the clinical significance of this environmental allergen. This study was approved by the Queen’ sU niversity Health Sciences and Affiliated Teaching Hospitals Research Ethics Board, with no financial interest or funding provided.

High Prevalence of Skin Test Positivity in Severe or Difficult-to-Treat Asthma

Background: Skin tests are considered the gold standard for detecting allergen-specific immunoglobulin E (IgE) in the clinical setting and are an important tool for diagnosing and managing allergic asthma. Objective: To assess the prevalence of skin testing in patients ≥ 12 years enrolled in The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens (TENOR) study. Methods: Patients were asked whether they had ever been skin tested and, if so, they were asked to provide the test results. Clinical characteristics were used to compare positive (ST+), negative (ST−), and skin test not done (STND) patients. Results: Of 2,985 patients eligible, 85.8% recalled being skin tested. Of those tested, 93.5% were positive (allergist 95.7%, pulmonologist 87.3%). A high proportion of Whites (93.5%) and non-Whites (94.0%) were ST+; however, more non-Whites had never been skin tested (21.7% vs. 12.3%, respectively; p < 0.0001). Total serum IgE was 104.6 IU/mL for ST+ patients, 87.1 IU/mL for STND patients, and 32.4 IU/mL for ST− patients. Age at asthma onset, duration of asthma, and the prevalence of atopic disorders and asthma triggers differentiated the ST+ from the ST− group. Disease severity appeared similar between the two groups. In general, values for STND patients were closer to the ST+ group, suggesting that those not tested would have been ST+ if administered a test. Conclusions: The prevalence of ST+ patients was high in allergy and pulmonology practices, and in White and non-White patients. These data support the utility of a more complete allergic evaluation in severe asthmatics. Skin testing appears associated with disease pathophysiologies in asthma.

Cannabis (hemp) positive skin tests and respiratory symptoms

We have noted several patients who had rhinitis and/or asthma symptoms when exposed to Cannabis plants in the summer months. Cannabis plants are common in the Midwest. To examine whether Cannabis might be a clinically important allergen, we determined Cannabis pollination patterns in the Omaha area for 5 years, the prevalence of skin test positivity, and the association with respiratory symptoms. Airborne Cannabis (and other weed) pollens were collected using a Rotorod air impactor, and pollen counts were done using a standardized protocol. Measurable Cannabis pollen count was not recorded until the last 2 weeks of July. Peak pollination typically occurred during mid- to late-August, and comprised up to 36% of the total pollen counts. Cannabis pollen was not observed after mid-September. To determine the prevalence of skin test positivity, we added Cannabis to the multi-test routine skin test battery. Seventy-eight of 127 patients tested (61%) were skin test positive. Thirty of the 78 patients were randomly selected to determine if they had allergic rhinitis and/or asthma symptoms during the Cannabis pollination period. By history, 22 (73%) claimed respiratory symptoms in the July through September period. All 22 of these subjects were also skin test positive to weeds pollinating during the same period as Cannabis (ragweed, pigweed, cocklebur, Russian thistle, marsh elder, or kochia). The strong association between skin test reactivity, respiratory symptoms, and pollination period suggests that Cannabis could be a clinically important aeroallergen for certain patients and should be further studied.

Delayed-type hypersensitivity to Mycobacterium leprae soluble antigens as a test for infection with the leprosy bacillus.

Mycobacterium leprae (M. leprae) soluble antigen (MLSA) reagents have been developed with the aim of finding a reagent, comparable to tuberculin, which could identify individuals infected with the leprosy bacillus. They have yet to be evaluated fully in human populations. More than 15000 individuals living in a leprosy endemic area of northern Malawi were skin tested with one of five batches of MLSA prepared using two different protocols. The main difference in preparation was the introduction of a high G centrifugation step in the preparation of the last three ('second-generation') batches. The prevalence of skin-test positivity (delayed-type hypersensitivity (DTH)) and association with the presence of a BCG scar were greater for first (batches A6, A22) than second (batches AB53, CD5, CD19) generation reagents. The association of positivity with M. leprae infection was investigated by comparing results among known (household) contacts of leprosy cases, and among newly diagnosed leprosy patients with those in the general population. While positivity to 'first-generation' antigens appeared to be associated with M. leprae infection, positivity to later antigens was unrelated either to exposure to leprosy cases or presence of leprosy disease. There were geographical differences in the prevalence of DTH to the various batches, probably reflecting exposure to various mycobacteria in the environment. Our results suggest that the 'second-generation' batches have lost antigens that can detect M. leprae infections, but that they retain one or more antigens which are shared between M. leprae and environmental mycobacteria. Natural exposure to these both sensitizes individuals and provides natural protection against M. leprae infection or disease. Identification of antigens present in these groups of skin test reagents may assist in production of improved skin test reagents.

Prevalence of Skin-Test Positivity to Cypress Pollen in Patients with Allergic Respiratory Diseases

Prevalence of Skin-Test Positivity to Cypress Pollen in Patients with Allergic Respiratory Diseases

Longitudinal changes in skin-prick test reactivity over 2 years in a population of schoolchildren with respiratory symptoms.

As part of a larger epidemiological study, 114 children with respiratory symptoms, born between 1978 and 1980, were skin-prick tested to Dermatophagoides pteronyssinus (DP), mixed grass pollens (G) and cat dander (C), and to histamine and saline controls (Bencard, U.K.) using 1 mm prick-lancets (Dome/Hollister-Stier), between July and September 1987 and again in October 1989. A weal > or = 2 mm to one or more allergens was regarded as a positive result. Each child was tested by the same investigator on each occasion, using similar techniques. Three children were excluded from analysis as they had failed to respond to histamine testing on one of the two occasions. In 1987, of the 111 children analysed, 58 (52%) children were skin-test positive, and 53 (48%) skin-test negative, while in 1989 62 (56%) were positive and 49 (44%) negative. Twelve children (11%) changed status from negative to positive, while eight (7%) changed from positive to negative. For the group as a whole the percentage agreement between the results obtained 2 years apart was 82%. In comparison to previous studies a greater number of subjects in this population than expected changed atopic status. We therefore further examined the data from those who had changed status and classified as borderline those subjects with no difference in weal size of greater than 2 mm for any allergen between 1987 and 1989. Only five children then changed status from negative to positive, none from positive to negative and 15 demonstrated only borderline changes. The coefficients of repeatability for the 106 children who did not change status were 3.37 mm, 2.80 mm and 2.33 mm for D. pteronyssinus, mixed grass pollens and cat dander respectively. The good short-term repeatability of the testing method was demonstrated in a group of 29 similar children; the coefficients of repeatability were 0.38 mm for DP and G, and 0.72 mm for C. These data demonstrate that, in a population of children with respiratory symptoms, skin-prick testing within individuals is highly repeatable over the short term, but poorly repeatable over a 2 year period. However, the percentage agreement in skin-prick test status for the group as a whole was high (82%). While no child became unequivocally skin-test negative having been previously positive, a small number of children changed status from negative to unequivocally positive, suggesting a genuine but small (4%) increase in the prevalence of skin-test positivity in this population.