Non-invasive tools beyond lung function before and after specific inhalation challenges for diagnosing occupational asthma.

PURPOSE: Increases of fractional exhaled nitric oxide (FeNO), sputum eosinophils, and methacholine responsiveness have been described after specific inhalation challenges (SIC) with occupational allergens, but limited information is available about their comparative performance. It was the aim of the study to assess the diagnostic accuracy of these non-invasive tests before and after SIC for the diagnosis of occupational asthma (OA). METHODS: A total of 122 subjects with work-related shortness of breath were included. The 'gold standard' was defined as airway obstruction (pulmonary responders) and/or an increase of FeNO of at least 13 ppb after SIC. The results were compared with those obtained using the pulmonary responder status alone as 'gold standard'. RESULTS: If the pulmonary responder status and/or an increase of FeNO was used as 'gold standard' for SIC, 28 out of 39 positives (72%), but also 20 out of 83 negatives (24%) showed an increase of sputum eosinophils and/or bronchial hyperresponsiveness after SIC. If the pulmonary responder status alone was used as 'gold standard', an increase of FeNO with a sensitivity of 0.57 and a specificity of 0.82 showed a higher accuracy than increases of sputum eosinophils (0.52/0.75) or bronchial hyperresponsiveness (0.43/0.87). Individual case analyses suggest that a few cases of OA may be detected by increases of sputum eosinophils or bronchial hyperresponsiveness alone, but probably false-positive tests dominate. CONCLUSION: It is recommended to use both lung function and increase of FeNO as primary effect parameters of SIC. Changes of sputum eosinophils and bronchial hyperresponsiveness after SIC have a low additional diagnostic value, but may be useful in individual cases.

Airway inflammation after inhalation of nano-sized zinc oxide particles in human volunteers.

BACKGROUND: Workers in the zinc production and processing of galvanized sheet steel are exposed to a complex mixture of particles and gases, including zinc oxide (ZnO) that can affect human health. We aimed to study the effects of short-term controlled exposure to nano-sized ZnO on airway inflammatory markers in healthy volunteers. METHODS: Sixteen subjects (8 females, 8 men; age 19-42, non-smokers) were exposed to filtered air and ZnO nanoparticles (0.5, 1.0 and 2.0 mg/m3) for 4 h, including 2 h of cycling with a low workload. Induced sputum samples were collected during a medical baseline and a final examination and also about 24 h after each exposure. A number of inflammatory cellular and soluble markers were analyzed. RESULTS: Frequency and intensity of symptoms of airway irritation (throat irritation and cough) were increased in some subjects 24 h after ZnO exposures when compared to filtered air. The group comparison between filtered air and ZnO exposures showed statistically significant increases of neutrophils and interleukin-8 (IL-8), interleukin-6 (IL-6), matrix metalloproteinase (MMP-9) and tissue inhibitors of metalloproteinases (TIMP-1) in sputum starting at the lowest ZnO concentration of 0.5 mg/m3. However, a concentration-response relationship was absent. Effects were reversible. Strong correlations were found between neutrophil numbers and concentrations of total protein, IL-8, MMP-9, and TIMP-1. CONCLUSIONS: Controlled exposures of healthy subjects to ZnO nanoparticles induce reversible airway inflammation which was observed at a concentration of 0.5 mg/m3 and higher. The lack of a concentration-response relationship warrants further studies.

Concentration-dependent systemic response after inhalation of nano-sized zinc oxide particles in human volunteers.

BACKGROUND: Inhalation of high concentrations of zinc oxide particles (ZnO) may cause metal fume fever. In an earlier human inhalation study, no effects were observed after exposure to ZnO concentrations of 0.5 mg/m3. Further data from experimental studies with pure ZnO in the concentration range between 0.5 and 2.5 mg/m3 are not available. It was the aim of this experimental study to establish the concentration-response relationship of pure nano-sized ZnO particles. METHODS: Sixteen healthy subjects were exposed to filtered air and ZnO particles (0.5, 1.0 and 2.0 mg/m3) for 4 h on 4 different days, including 2 h of cycling with a low workload. The effects were assessed before, immediately after, and about 24 h after each exposure. Effect parameters were symptoms, body temperature, inflammatory markers and clotting factors in blood, and lung function. RESULTS: Concentration-dependent increases in symptoms, body temperature, acute phase proteins and neutrophils in blood were detected after ZnO inhalation. Significant effects were detected with ZnO concentrations of 1.0 mg/m3 or higher, with the most sensitive parameters being inflammatory markers in blood. CONCLUSION: A concentration-response relationship with nano-sized ZnO particles in a low concentration range was demonstrated. Systemic inflammatory effects of inhaled nano-sized ZnO particles were observed at concentrations well below the occpational exposure limit for ZnO in many countries. It is recommended to reassess the exposure limit for ZnO at workplaces.

An increase of fractional exhaled nitric oxide after specific inhalation challenge is highly predictive of occupational asthma.

PURPOSE: An increase of fractional exhaled nitric oxide (FeNO) has been described after specific inhalation challenges (SICs) with occupational allergens, but the clinical role of FeNO measurements before and after SIC is unknown. It was the aim of this study to assess the diagnostic accuracy of FeNO measurements before and after SIC in subjects with suspected occupational asthma (OA). METHODS: One hundred forty-eight patients with suspected OA were examined by SIC with various occupational allergens. Subjects were assigned to pulmonary responders, nonresponders or doubtful by standard lung function criteria. FeNO was measured before SIC (baseline) and 24 h afterwards. Subjects with negative or doubtful SIC but increase of FeNO were evaluated individually by an overall expert rating. Effect modifiers of FeNO increases were assessed by regression analyses. RESULTS: Thirty-one patients (21%) were classified as pulmonary responders, 105 (71%) as nonresponders and 12 (8%) as doubtful. With the pulmonary responder status as gold standard an increase of FeNO ≥ 13 ppb showed a specificity of 0.9 and a sensitivity of 0.5. Seventeen subjects with negative or doubtful responder status showed such an increase of FeNO, among them 13 subjects with definitive or probable OA after expert rating. Regression analyses revealed no significant modifiers for the FeNO increase. CONCLUSION: An increase of FeNO after SIC is highly predictive of OA and should be regarded as an additional criterion for the interpretation of SIC with occupational agents.

Cell Activation and Cytokine Release Ex Vivo: Estimation of Reproducibility of the Whole-Blood Assay with Fresh Human Blood.

The whole-blood assay (WBA) with human fresh blood may provide insight into the features of an individual's innate immunity. To assess this, ex vivo cytokine release is measured after stimulation of whole blood with various stimuli, for instance, endotoxin in vitro. The aim of the present study was to evaluate WBA reproducibility with fresh blood using different calculation models. The blood was collected from 16 healthy volunteers on 6 different days. Ex vivo stimulation was performed in each individual's blood sample for 22 h, using different endotoxin concentrations. Interleukin (IL)-1ß and IL-8 release were quantified using specific immunoassays in the cell-free supernatant. We found that a dose-response relationship between endotoxin and cytokine concentration could be verified for all blood donors in all tests. The median coefficient of variation of the repeated tests was 29% for IL-1ß and 52% for IL-8. Upon stimulation with 40 pg/mL endotoxin, a confidence interval of 60-140% was calculated for IL-1ß and 70-271% for IL-8 regarding test reproducibility. Furthermore, the classification into high or low responder was reproducible. We conclude that repeated blood collection offers an opportunity to evaluate the variability of WBA. Considering a high intragroup variability, an individual range assessment has been suggested to evaluate exposure effects.

Heart rate variability and cardiac repolarization after exposure to zinc oxide nanoparticles in healthy adults.

BACKGROUND: Exposure to airborne zinc oxide (ZnO) particles occurs in many industrial processes, especially in galvanizing and welding. Systemic inflammation after experimental inhalation of ZnO particles has been demonstrated previously, but little is known about the impact on the cardiovascular system, particularly on the autonomic cardiac system and the risk of arrhythmias. In this study we investigated the short-term effects of ZnO nanoparticles on heart rate variability (HRV) and repolarization in healthy adults in a concentration-dependent manner at rest and during exercise in a controlled experimental set-up. METHODS: Sixteen healthy subjects were exposed to filtered air and ZnO particles (0.5, 1.0 and 2.0 mg/m3) for 4 h, including 2 h of cycling at low workloads. Parameters were assessed before, during, immediately after, and about 24 h after each exposure. For each subject, a total number of 46 10-min-sections from electrocardiographic records were analyzed. Various parameters of HRV and QT interval were measured. RESULTS: Overall, no statistically significant effects of controlled ZnO inhalation on HRV parameters and QT interval were observed. Additionally, a concentration-response was absent. CONCLUSION: Inhalation of ZnO nanoparticles up to 2.0 mg/m3 for 4 h does not affect HRV and cardiac repolarization in healthy adults at the chosen time points. This study supports the view that cardiac endpoints are insensitive for the assessment of adverse effects after short-term inhalation of ZnO nanoparticles.