Category Archives: Allergens

Inhalation Challenge With Bovine Dander Allergens: Conclusion

None of the six subjects who did not have a doctor’s diagnosis of asthma responded to bSICs. Although the number of these patients was small, this finding suggests that the diagnosis of asthma should be established clearly before referring a subject for an SIC. This recommendation is present, though not emphasized, in international guide-lines. An objective confirmation of asthma before considering an SIC may be especially important in farmers, who have a high prevalence of lower airway respiratory symptoms that often are of nonasthmatic origin.

Inhalation Challenge With Bovine Dander Allergens: Inhaled mannitol

Inhalation Challenge With Bovine Dander Allergens: Inhaled mannitolThese features of the farming environment probably explain the low specificity of histamine challenge in the diagnosis of bovine asthma, and the poor correlation between histamine reactivity and responsiveness to bSICs. It seems clear that bronchial hyperreactivity in a farmer is not an indication to perform an SIC.
It has been suggested that an indirectly acting bronchial stimulus, like mannitol, would better reflect the degree of airway inflammation than a direct-acting stimulus like histamine.

Inhalation Challenge With Bovine Dander Allergens: Bronchial hyperreactivity

Although the specificity of a positive SPT result was poor, the sensitivity was high, and the NPV was 100% (ie, none of the subjects with an SPT wheal of < 3 mm responded to bSICs). In the study of Taivainen et al, the sensitivity of SPT was 94%. Thus, a negative result in SPT virtually excludes bovine asthma.

Inhalation Challenge With Bovine Dander Allergens: PPV

Inhalation Challenge With Bovine Dander Allergens: PPVOur finding reflects the special difficulties the clinicians encounter when assessing the probability of occupational asthma among farmers and highlights a need for screening tests. We were able to demonstrate that simple tests, namely, SPTs and bIgE tests, can be used effectively for selecting patients for bSICs. These findings are clinically important, not only from the viewpoint of avoiding a challenge with potential for prolonged effects but also from an economic viewpoint, because challenge requires inpatient care and time lost from work. add comment

Inhalation Challenge With Bovine Dander Allergens: Discussion

The main results are expressed in Tables 1 and 2. The NPV for an SPT response to a bovine solution for skin testing of < 3 mm was 100%, and the PPV of a bIgE of > 5 IU/L was 100% (Fig 1). In the simple regression analysis, SPT response to bovine solution for inhalation challenges was shown to have the strongest association with RDR-bSIC (r = 0.65; p < 0.0001; Fig 2). The association between bIgE and RDR-bSIC (r = 0.59; p = 0.0001; Fig 3) was also clearly stronger than that between the RDR of the histamine challenge and RDR-bSIC (r = 0.30; p = 0.07; Fig 4). The RDR of the mannitol challenge, NO level, or prechallenge FEV1 percent of predicted did not show a statistically significant association with RDR-bSIC.

Inhalation Challenge With Bovine Dander Allergens: Statistical Analysis

Inhalation Challenge With Bovine Dander Allergens: Statistical AnalysisThe results are expressed as the mean and 95% CI. The RDR, PC, and PD values, as well as the IgE and NO concentrations, are geometric means with 95% CIs. These values were log-transformed before all statistical analysis.
The comparison between responders and nonresponders was performed using the Student t test.

Inhalation Challenge With Bovine Dander Allergens: bSIC

Spray-dried mannitol powder, packed in gelatin capsules containing 5 to 40 mg, was inhaled by the patient using an inhalator (Boehringer Ingelheim Pty LTD; Ingelheim, Germany) until the FEV1 had fallen 15%, or until the maximal dose of 635 mg had been administered. The provocative dose (PD) of a substance causing a 15% fall in FEV1 was calculated as described, but the RDR values were calculated using cumulative doses. A cutoff value for a positive response was defined as a fall in FEVX of > 15%.

Inhalation Challenge With Bovine Dander Allergens: Histamine Challenge

Inhalation Challenge With Bovine Dander Allergens: Histamine ChallengeHistamine challenge was performed according to the method of Cockcroft et al but using a dosimetric nebulizer (Spira Electro 2; Respiratory Care Center; Hameenlinna, Finland). The nebulization time was 0.4 s, and was set to start 100 mL after the beginning of inspiration. The peak inspiratory flow did not exceed 0.5 L/s. The nebulization pressure was 200 kPa. These settings gave a calibrated output of 6.5 |j,L per inhalation. First, spirometry was performed three times.

Inhalation Challenge With Bovine Dander Allergens: SPTs

On the fifth day, a bSIC was performed. If the result of the bSIC was negative, and if the prestudy SPTs had shown sensitization to some other agricultural allergens, an SIC using the allergen with the greatest skin reaction was performed on the next day. All inhalation challenges were performed at the same time of the day. The patient left the ward on the day after undergoing the last inhalation challenge.

Inhalation Challenge With Bovine Dander Allergens: Study Design

Inhalation Challenge With Bovine Dander Allergens: Study DesignExclusion criteria were unstable asthma, FEV1 < 65% of predicted, and respiratory tract infection within the last 6 weeks. One patient was excluded because he had responded positively to a sham challenge. The basic characteristics of the remaining 37 subjects are given in Table 1. Before hospital admission, 30 patients had a doctor’s diagnosis of asthma. SPTs for common and agricultural allergens (ie, cow, storage mites, rye, oat, wheat, and barley) had been performed before the study (Soluprick SQ; ALK Abello; Horsholm, Denmark).

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