Determinants of the bronchial response to high molecular weight occupational agents in a dry aerosol form

Specific inhalation challenge: the relationship between response, clinical variables and lung function

INTRODUCTION

The specific inhalation challenge (SIC) is considered the gold standard for the diagnosis of occupational asthma (OA). However, its use is not standardised, and the intensity of exposure is regulated empirically. The aim of this study was to identify clinical variables and/or pulmonary function variables able to predict the scale of patients' response to SIC.

MATERIAL AND METHODS

All patients who underwent SIC at our centre between 2005 and 2013 were studied. Anthropometric characteristics, atopic status, type of causal agent, latency times, pulmonary function tests and SIC results were analysed.

RESULTS

Two hundred and one patients (51% men) were assessed, of whom 86 (43%) had positive SIC. In the patients with positive results, 29 (34%) were exposed to high molecular weight (HMW) agents and 57 (64%) to low molecular weight (LMW) agents. Patients with a positive SIC exposed to HMW agents had a higher fall in FEV₁ after SIC compared with those exposed to LMW agents (p=0.036). The type of asthmatic reaction after SIC also differed between the groups (p=0.020). The logistic regression analysis showed that patients with a higher PC₂₀ before SIC were less likely to have severe decreases in FEV1 after SIC after adjusting for potential confounders (OR=0.771, 95% CI 0.618 to 0.961, p=0.021).

CONCLUSIONS

The scale of the response to SIC is influenced mainly by the degree of bronchial hyper-responsiveness, regardless of whether the causative agent is HMW or LMW, or whether the response is early or late.

Inhalation challenges with occupational agents: threshold duration of exposure

OBJECTIVES

The aim of this study was to characterize the threshold duration of exposure needed to elicit an asthmatic reaction during specific inhalation challenges (SIC) with various occupational agents and to determine the duration of exposure that should be completed before the test can be considered negative.

METHODS

This retrospective study analysed the cumulative duration of challenge exposure that was required to elicit a ≥20% fall in forced expiratory volume in one second in 335 consecutive subjects with a positive SIC.

RESULTS

The threshold duration of challenge exposure required to induce an asthmatic reaction was ≤60 min in 179 (53%) subjects, between 61 and 120 min in 74 (22%) subjects, and longer than 120 min in 82 (25%) subjects. The multivariate linear regression analysis showed that a longer duration of exposure was associated with exposure to low-molecular-weight agents (p < 0.001), a higher level of baseline non-specific bronchial hyperresponsiveness to histamine (p = 0.015), increasing age (p = 0.011), and a shorter duration of asthma symptoms at work (p = 0.060).

CONCLUSIONS

This study demonstrates that the sensitivity of SICs for diagnosing OA is highly dependent upon the duration of the challenge exposure. These data may provide useful guidance for improving the reliability of SICs performed with realistic methods of exposure.

Diagnosis and prevention of diseases induced by isocyanate

Isocyanates are among the most frequent causes of occupational asthma in industrialized countries. Early diagnosis of diisocyanate asthma followed by prompt termination of chemical exposure can prevent chronic morbidity due to persistent asthma. Chronic exposure to isocyanates also induces hypersensitivity pneumonitis (HP). The accurate diagnosis of diisocynate asthma requires a systematic approach that combines information obtained from the occupational history, immunologic tests and physiologic studies. The prevention of health problems from toluene diisocyanate (TDI), 4,4'-methylenediphenyl diisocyanate (MDI) and 1,6'-hexamethylene diisocyanate (HDI) is essential for all those handling the chemicals. Regulatory exposure limits should be observed. However, wheezing, coughing or even asthmatic attacks may occur after exposure much below the regulatory exposure limits especially in sensitive individuals. Preventing or minimizing exposure is of prime importance and should be supported by the installation of engineering controls, by education of the workforce, by regular monitoring of the workplace exposure and by medical surveillance. To prevent such asthma it is suggested that workers should be tested airway sensitivity and should avoid working in areas that have dust containing specific-IgE. Such tests must be periodically performed after working. Symptoms induced by isocyanate need earlier discover and early isolation of the associated individuals.

Rye flour induces a stronger early bronchial response than wheat flour in occupational asthma

BACKGROUND

Our aims were to compare the doses of wheat and rye flour that induce early bronchial responses in occupationally exposed asthmatic subjects and to assess the effects of the dose of inhaled flour, the duration of exposure and the dose rate.

METHODS

Ten patients underwent tests with lactose, wheat flour and rye flour. We compared the decrease in forced expiratory volume in 1 s (FEV(1)) observed during the challenge with flour and with lactose. We also calculated the amount of flour that was instantaneously active.

RESULTS

Seven subjects had significantly decreased FEV(1) values following exposure to wheat and rye flour and two subjects only did so for rye flour. The provocative dose (PD, dose required to reduce FEV(1) by 15%) of rye was lower than that of wheat flour (geometric mean; PD(15) rye: 95 microg; wheat: 368 microg). The calculated doses of rye and wheat flour were better correlated with the change in FEV(1) than were the cumulative doses.

CONCLUSION

The bronchial response was greater with rye than with wheat flour. The response was related to the dose of allergen inhaled and to the dose rate.

Psyllium-associated anaphylaxis and death: a case report and review of the literature

BACKGROUND

Psyllium use has increased significantly in the United States in part due to its lipid-lowering property. The increased prevalence of consumption has led to its recognition as an emerging food allergen.

OBJECTIVES

To report the case of a 42-year-old woman who experienced fatal anaphylaxis after ingesting a psyllium-based product and to review the literature.

METHODS

The MEDLINE database was searched for articles from 1966 to 2002 using the keywords psyllium or ispaghula and each of the following: allergy, hypersensitivity, anaphylaxis, and asthma. Both English and non-English articles were included.

RESULTS

Psyllium hypersensitivity has been well described in health care workers and pharmaceutical plant employees. Clinical manifestations of allergy range from upper respiratory tract symptoms on inhalation to anaphylaxis on ingestion. The prevalence of sensitization varies between these 2 groups. The allergenic epitope is not known.

CONCLUSIONS

We present a case of psyllium hypersensitivity that resulted in death. There is a clear association between atopy and psyllium allergy. The case underscores the fact that even nonprescription "natural" products can be harmful to people with allergies.

Recent advances in occupational asthma

In the past year, many advances were made in occupational asthma (OA). As in previous years, several new causes of OA were described and the prevalences of some causes of OA were studied. Animal studies suggested possible mechanisms for the induction of sensitization to low-molecular-weight chemicals, and a study in humans indicated the ability of diisocyanates to bind with lung epithelial cells and stimulate mononuclear cells in sensitized patients with OA. New diagnostic and research methods, such as induced-sputum assessment and measurement of exhaled nitric oxide, were evaluated. The effectiveness of protective respiratory devices in patients with OA was shown to be suboptimal (although these devices are necessary in some cases), and the need to prevent OA by reducing or eliminating exposures remains paramount.