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Interferon (IFN)-γ release assays (IGRAs) are probably the most accurate tests for the detection of latent Mycobacterium tuberculosis infection, but IGRAs are labour intensive and the transport of samples over longer distances is difficult. IFN-γ-induced protein (IP)-10 is expressed at 100-fold higher levels than IFN-γ, and IP-10 release assays have comparable performance to IGRAs. The aim of this study was to explore the diagnostic potential of a novel IP-10 release assay based on dried plasma spots (DPS). The presence of IP-10 and IFN-γ was determined in plasma and in DPS by ELISA. Diagnostic algorithms for plasma and DPS tests for IP-10 were developed on a training cohort comprising 60 tuberculosis (TB) patients and 59 healthy controls. Diagnostic accuracy was assessed in a validation cohort comprising 78 TB patients and 98 healthy controls. Plasma was measured in Spain and DPS samples were sent to Denmark using the conventional postal service for analysis. IP-10 was readily detectable in both plasma and DPS, and correlation was excellent (r(2) = 0.95). QuantiFERON-TB Gold In-Tube (QFT-TB) and IP-10 in DPS and plasma rendered comparable sensitivity (78%, 82% and 84%, respectively), specificity (100%, 97% and 97%, respectively) and indeterminate rates (p>0.55). The DPS-based IP-10 test has comparable diagnostic accuracy to the QFT-TB and samples can be sent via conventional mail over long distances for analysis without affecting the results.

The aim of the present study was to investigate whether repeated peak exposure (gassings) to sulphur dioxide (SO2) and other irritant gases increases the risk of new-onset asthma. A questionnaire was sent to 4,112 sulphite workers, of whom 1,919 completed the questionnaire and 396 completed the short-form questionnaire, which was sent out as a last reminder. A sample of 130 nonrespondents completed a telephone interview using the short-form questionnaire. The incidence of adult-onset, physician-diagnosed asthma during employment duration was analysed in relation to exposure to SO2 and gassings giving rise to respiratory symptoms. Incidence rates, as well as incidence rate ratios with 95% confidence interval (CI), were calculated. Further Cox regression models were used allowing assessment of hazard ratios (HR) stratified for sex and adjusted for atopy, smoking habits and age. The incidence rate for asthma among sulphite mill workers reporting gassings of SO2 was 6.2 out of 1,000 person-yrs, compared with 1.9 out of 1,000 person-yrs among subjects unexposed to SO2 and any gassings (HR (95% CI) 4.0 (2.1-7.7)). Among males reporting gassings to SO2, the HR (95% CI) for asthma was 5.8 (2.6-13) compared with unexposed males. In conclusion, repeated peak exposure to sulphur dioxide increased the incidence of asthma during work in sulphite pulp mills, which supports the hypothesis of irritant-induced asthma.

This study investigated whether chronic airflow limitation and rapid decline in pulmonary function were associated with peak exposures to ozone and other irritant gases in pulp mills. Bleachery workers potentially exposed to irritant gassings (n = 178) from three Swedish pulp mills, and a comparison group of workers not exposed to irritant gassings (n = 54) from two paper mills, were studied. Baseline surveys occurred in 1995-1996, with follow-up surveys in 1998-1999. Participants performed spirometry and answered questions regarding ozone, chlorine dioxide (ClO2), and sulphur dioxide (SO2) gassings. From regression models controlling for potential confounders, declines in both the forced expiratory volume in one second (FEV1) (-24 mL x yr(-1)) and the forced vital capacity (FVC) (-19 mL x yr(-1)) were associated with ClO2/SO2 gassings. At follow-up, the prevalence of chronic airflow limitation (i.e. FEV1/FVC less than the lower limit of normal) was elevated for participants with only pre-baseline ozone gassings and with both pre-baseline and interval ozone gassings, after controlling for potential confounders. These findings suggest that obstructive effects among bleachery workers are associated with ozone gassings, and that adverse effects on spirometry might also accompany chlorine dioxide/sulphur dioxide gassings. Peak exposures to irritant gases in pulp mills should be prevented.

The aim of the study was to investigate whether measurement of nitric oxide in exhaled air could be used for assessing the effects of irritants on the respiratory system, in this case recurrent ozone gassing in an occupational setting. The study population comprised bleachery workers (n=56) from a Swedish pulpmill carrying out ozone-based pulp bleaching since 1992 and controls (n=39). Both groups were investigated by measuring NO in exhaled air, methacholine challenge test and answers to a questionnaire concerning history of respiratory symptoms and accidental exposure to ozone peaks. There was no significant difference in NO output between exposed subjects and controls (median 67.2 versus 55.0 nL x min(-1), p=0.64). However, among bleachery workers reporting ozone gassings, the median NO output was 90.0 nL x min(-1) compared to 58.8 nL x min(-1) among those not reporting such incidents (p=0.019). There was no relation between exhaled NO and the prevalence of respiratory symptoms or bronchial hyperresponsiveness. In a multiple regression model, only reported ozone gassings were associated (p=0.016) with NO output. The results indicate an association between previous response to ozone gassing and nitric oxide output. The increased nitric oxide output among the bleachery workers reporting peak ozone exposure may indicate that chronic airway inflammation is present. Further studies are needed to evaluate the extent to which nitric oxide can be used for biological monitoring of respiratory health effects, and to relate it to other markers of airway inflammation.

Exposure to organic dusts may cause airways inflammation in a large proportion of exposed persons. Most studies have relied on questionnaires and spirometry for diagnosis. To assess the possibility of determining the presence of inflammation using clinical diagnostic procedures, a study was undertaken among workers in a paper industry. Participants were 83 workers and 44 controls. Airborne endotoxin and (1-->3)-beta-D-glucan levels at the worksites were determined. The effects of this exposure were evaluated using a questionnaire, spirometry and measurements of airway responsiveness (methacholine) and levels of eosinophil cationic protein (ECP), myeloperoxidase (MPO), and C-reactive protein (CRP) in serum. The workers had a decreased baseline forced expiratory volume in one second (FEV1) and an increased airway responsiveness compared with controls. The concentrations of ECP and MPO were elevated compared with controls. There was a relation between exposure to endotoxin and (1-->3)-beta-D-glucan and airway responsiveness as well as ECP levels, when controlling for age, sex, smoking habits, atopy and asthma. The results suggest an increased prevalence of subjective respiratory symptoms, and an increased airway responsiveness among exposed workers. There was also a relationship between the serum concentration of eosinophil cationic protein and airway responsiveness. Taken together, the results suggest the presence of airways inflammation in the workers.