Development of OASYS-2: a system for the analysis of serial measurement of peak expiratory flow in workers with suspected occupational asthma

Occupational asthma in the salmon processing industry: a case series

OBJECTIVES

Exposure to bioaerosols in salmon processing workers is associated with occupational asthma. IgE-mediated allergy and other disease mechanisms may be involved in airway inflammation and obstruction. Knowledge about disease burden, mechanisms, phenotypes and occupational exposure is limited.

METHODS

Salmon processing workers referred to our occupational medicine clinic from 2019 to 2024 were included in a patient register. They were investigated in line with current guidelines for the management of occupational asthma, categorised according to diagnostic certainty and characterised with a focus on symptoms, work tasks and clinical findings.

RESULTS

A total of 36 patients were included, among whom 27 had typical symptoms of work-related asthma, and 21 were diagnosed with occupational asthma. Among those with occupational asthma, all worked in the filleting or slaughtering area at the time of symptom onset. Median latency from the start of exposure to symptom onset was 4 years. 14 (67%) of the patients with occupational asthma were sensitised to salmon. Three patients were sensitised to salmon skin but not salmon meat.

CONCLUSIONS

Occupational asthma among salmon processing workers displays a heterogeneous clinical picture. IgE-mediated inhalation allergy towards various parts of the salmon seems to represent an important pathophysiological mechanism. However, some have occupational asthma with negative allergy tests. A comprehensive workup strategy including early initiation of serial peak expiratory flow and skin prick tests with various parts of the salmon should be considered. Although the incidence remains unknown, the substantial number of cases presented warrant increased efforts to reduce harmful exposure in the salmon processing industry.

Effects of Interventions to Prevent Work-Related Asthma, Allergy, and Other Hypersensitivity Reactions in Norwegian Salmon Industry Workers (SHInE): Protocol for a Pragmatic Allocated Intervention Trial and Related Substudies

BACKGROUND

Workers in the salmon processing industry have an increased risk of developing respiratory diseases and other hypersensitivity responses due to occupational exposure to bioaerosols containing fish proteins and microorganisms, and related allergens. Little is known about effective measures to reduce bioaerosol exposure and about the extent of skin complaints among workers. In addition, while identification of risk factors is a core activity in disease prevention strategies, there is increasing interest in health-promoting factors, which is an understudied area in the salmon processing industry.

OBJECTIVE

The overall aim of this ongoing study is to generate knowledge that can be used in tailored prevention of development or chronification of respiratory diseases, skin reactions, protein contact dermatitis, and allergy among salmon processing workers. The main objective is to identify effective methods to reduce bioaerosol exposure. Further objectives are to identify and characterize clinically relevant exposure agents, identify determinants of exposure, measure prevalence of work-related symptoms and disease, and identify health-promoting factors of the psychosocial work environment.

METHODS

Data are collected during field studies in 9 salmon processing plants along the Norwegian coastline. Data collection comprises exposure measurements, health examinations, and questionnaires. A wide range of laboratory analyses will be used for further analysis and characterization of exposure agents. Suitable statistical analysis will be applied to the various outcomes of this comprehensive study.

RESULTS

Data collection started in September 2021 and was anticipated to be completed by March 2023, but was delayed due to the COVID-19 pandemic. Baseline data from all 9 plants included 673 participants for the health examinations and a total of 869 personal exposure measurements. A total of 740 workers answered the study's main questionnaire on demographics, job characteristics, lifestyle, health, and health-promoting factors. Follow-up data collection is not completed yet.

CONCLUSIONS

This study will contribute to filling knowledge gaps concerning salmon workers' work environment. This includes effective workplace measures for bioaerosol exposure reduction, increased knowledge on hypersensitivity, allergy, respiratory and dermal health, as well as health-promoting workplace factors. Together this will give a basis for improving the work environment, preventing occupational health-related diseases, and developing occupational exposure limits, which in turn will benefit employees, employers, occupational health services, researchers, clinicians, decision makers, and other stakeholders.

TRIAL REGISTRATION

ClinicalTrials.gov NCT05039229; https://www.clinicaltrials.gov/study/NCT05039229.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/48790.

Occupational asthma in teachers

BACKGROUND

Work-related asthma symptoms are common in teachers and teaching assistants, there are few studies evaluating their causes.

AIMS

To identify causes of occupational asthma in teachers and teaching assistants referred to the Birmingham Occupational Lung Disease clinic 2000-20 using evaluation of serial Peak Expiratory Flow (PEF) records.

METHODS

Teachers and teaching assistants with possible occupational asthma were asked to record PEF 2-hourly at home and work for 4 weeks. Their records were evaluated with the Oasys programme. Those with a positive score for any of the three scores (area between curves (ABC), timepoint and Oasys score from discriminant analysis) were included. Repeat records were made as indicated to help identify the cause and the effects of remedial actions.

RESULTS

Thirty-eight teachers or teaching assistants met the inclusion criteria with all three Oasys scores positive in 24, 2/3 scores in nine and 1/3 in five. The building was the likely cause in 17 (in new builds particularly acrylates from carpet adhesives and in old buildings mould and construction dust), bystander exposure to agents in the schools in 12 (cleaning agents, acrylates from photocopiers and chloramines from indoor pools) and materials used in the classroom in 9 (most commonly MDF in design and technology classes). We illustrate how the PEF records helped identify the cause.

CONCLUSIONS

Oasys analysis of PEF records is a useful method of evaluating occupational asthma in teachers and identified difficult to confirm causes where successful remediation or redeployment was achieved.

Occupational Asthma Caused by Low-Molecular-Weight Chemicals Associated With Contact Dermatitis: A Retrospective Study

BACKGROUND

Occupational asthma (OA) may have different etiologies, but it is not clear whether the etiologic agents influence the clinical presentation, especially the co-occurrence of skin lesions.

OBJECTIVE

To determine the impact of different asthmagens on the characteristics of OA, with a focus on the occurrence of prior or concomitant skin disorders.

METHODS

In a retrospective analysis of patients who visited the Occupational and Environmental Disease Clinic of a tertiary referral hospital from 2009 to 2019, we classified patients into definite, probable, or possible OA according to prespecified diagnostic guidelines. In multivariate logistic regression with sensitivity analysis, we examined the relation of high- and low-molecular-weight (HMW and LMW) agents with the clinical presentation.

RESULTS

Of 209 cases of OA, 66 were caused by HMW agents and 143 by LMW agents. Patients with OA exposed to LMW agents had higher odds of having (had) allergic contact dermatitis (odds ratio, 5.45 [1.80-23.70]; P < .01), compared with patients exposed to HMW agents. Conversely, HMW agents were associated with higher odds of rhinitis symptoms (odds ratio of LMW/HMW, 0.33 [0.17-0.63]; P < .001) and high total IgE (odds ratio of LMW/HMW, 0.35 [0.17-0.70]; P < .01). Risk factors for having coexisting contact dermatitis included construction work, hairdressing, and exposure to metals or epoxy resins.

CONCLUSIONS

Among patients with OA, exposure to specific LMW agents was associated with a high frequency of contact dermatitis. Different types of asthmagens within HMW or LMW agents appear to determine the phenotype and comorbidity of OA.

Pulmonary Function Testing in Work-Related Asthma: An Overview from Spirometry to Specific Inhalation Challenge

Work-related asthma (WRA) is a very frequent condition in the occupational setting, and refers either to asthma induced (occupational asthma, OA) or worsened (work-exacerbated asthma, WEA) by exposure to allergens (or other sensitizing agents) or to irritant agents at work. Diagnosis of WRA is frequently missed and should take into account clinical features and objective evaluation of lung function. The aim of this overview on pulmonary function testing in the field of WRA is to summarize the different available tests that should be considered in order to accurately diagnose WRA. When WRA is suspected, initial assessment should be carried out with spirometry and bronchodilator responsiveness testing coupled with first-step bronchial provocation testing to assess non-specific bronchial hyper-responsiveness (NSBHR). Further investigations should then refer to specialists with specific functional respiratory tests aiming to consolidate WRA diagnosis and helping to differentiate OA from WEA. Serial peak expiratory flow (PEF) with calculation of the occupation asthma system (OASYS) score as well as serial NSBHR challenge during the working period compared to the off work period are highly informative in the management of WRA. Finally, specific inhalation challenge (SIC) is considered as the reference standard and represents the best way to confirm the specific cause of WRA. Overall, clinicians should be aware that all pulmonary function tests should be standardized in accordance with current guidelines.

Diagnosis of occupational asthma from serial measurements of forced expiratory volume in 1 s (FEV1) using the Area Between Curves (ABC) score from the Oasys plotter

OBJECTIVES

To identify the changes in serial 2-hourly forced expiratory volume in 1 s (FEV₁) measurements required to identify occupational asthma (OA) using the Oasys Area Between Curves (ABC) score.

METHODS

The ABC score from 2-hourly measurements of FEV₁ was compared between workers with confirmed OA and asthmatics without occupational exposure to identify the optimum separation using receiver operator characteristic (ROC) analysis. Separate analyses were made for plots using clock time and time from waking to allow for use in shift workers. Minimum record criteria were ≥6 readings per day, >4 day shifts and >4 rest days (or >9 days for controls).

RESULTS

A retrospective analysis identified 22 workers with OA and 30 control asthmatics whose records reached the quality standards. Median FEV₁ diurnal variation was 20.3% (IQR 16.1-32.6) for OA and 19.5% (IQR 14.5-26.1) for asthmatic controls. ROC curve analysis identified that a difference of 0.056 L/hour gave a ROC score of 0.821 for clock time and 0.768 for time from waking with a sensitivity of 73% and a specificity of 93% for the diagnosis of OA.

CONCLUSIONS

The diagnosis of OA requires objective confirmation. Unsupervised serial FEV₁ measurements are more difficult to obtain reliably than measurements of peak expiratory flow, which are likely to remain the standard for general use. A FEV₁ ABC score >0.056 L/hour provides a valid cut-off for those who wish to use FEV₁ rather than peak expiratory flow.

Identification of late asthmatic reactions following specific inhalation challenge

Specific inhalation challenge (SIC) is the reference standard for the diagnosis of occupational asthma. Current guidelines for identifying late asthmatic reactions are not evidence based.

OBJECTIVES

To identify the fall in forced expiratory volume in 1 s (FEV₁) required following SIC to exceed the 95% CI for control days, factors which influence this and to show how this can be applied in routine practice using a statistical method based on the pooled SD for FEV₁ from three control days.

METHODS

Fifty consecutive workers being investigated for occupational asthma were asked to self-record FEV₁ hourly for 2 days before admission for SIC. These 2 days were added to the in-hospital control day to calculate the pooled SD and 95% CI.

RESULTS

45/50 kept adequate measurements. The pooled 95% CI was 385 mL (SD 126), or 14.2% (SD 6.2) of the baseline FEV₁, but was unrelated to the baseline FEV₁ (r=0.06, p=0.68), or gender, atopy, smoking, non-specific reactivity or treatment before or during SIC. Thirteen workers had a late asthmatic reaction with ≥2 consecutive FEV₁ measurements below the 95% CI for pooled control days, 4/13 had <15% and 9/13 >15% late fall from baseline. The four workers with ≥2 values below the 95% CI all had independent evidence of occupational asthma.

CONCLUSION

The pooled SD method for defining late asthmatic reactions has scientific validity, accounts for interpatient spirometric variability and diurnal variation and can identify clinically relevant late asthmatic reactions from smaller exposures. For baseline FEV₁ <2.5 L, a 15% fall is within the 95% CI.

Occupational asthma; the limited role of air-fed respiratory protective equipment

BACKGROUND

Evidence-based reviews have found that evidence for the efficacy of respiratory protective equipment (RPE) in the management of occupational asthma (OA) is lacking.

AIMS

To quantify the effectiveness of air-fed RPE in workers with sensitizer-induced OA exposed to metal-working fluid aerosols in a car engine and transmission manufacturing facility.

METHODS

All workers from an outbreak of metal-working fluid-induced OA who had continuing peak expiratory flow (PEF) evidence of sensitizer-induced OA after steam cleaning and replacement of all metal-working fluid were included. Workers kept 2-hourly PEF measurements at home and work, before and after a strictly enforced programme of RPE with air-fed respirators with charcoal filters. The area-between-curve (ABC) score from the Oasys plotter was used to assess the effectiveness of the RPE.

RESULTS

Twenty workers met the inclusion criteria. Records were kept for a mean of 24.6 day shifts and rest days before and 24.7 after the institution of RPE. The ABC score improved from 26.6 (SD 16.2) to 17.7 (SD 25.4) l/min/h (P > 0.05) post-RPE; however, work-related decline was <15 l/min/h in only 12 of 20 workers, despite increased asthma treatment in 5 workers.

CONCLUSIONS

Serial PEF measurements assessed with the ABC score from the Oasys system allowed quantification of the effect of RPE in sensitized workers. The RPE reduced falls in PEF associated with work exposure, but this was rarely complete. This study suggests that RPE use cannot be relied on to replace source control in workers with OA, and that monitoring post-RPE introduction is needed.

Cleaning agent occupational asthma in the West Midlands, UK: 2000-16

Background

Cleaning agents are now a common cause of occupational asthma (OA) worldwide. Irritant airway and sensitization mechanisms are implicated for a variety of old and new agents.

Aims

To describe the exposures responsible for cleaning agent OA diagnosed within a UK specialist occupational lung disease service between 2000 and 2016.

Methods

The Birmingham NHS Occupational Lung Disease Service clinical database was searched for cases of OA caused by cleaning agents, and data were gathered on age, gender, atopic status, smoking history, symptom onset, diagnostic investigations (including Occupational Asthma SYStem analysis of workplace serial peak expiratory flow measurements and specific inhalational challenge), proposed mechanism, industry, occupation and causative agent.

Results

Eighty patients with cleaning agent OA (77% female, 76% arising de novo) were identified. The median annual number of cases was 4 (interquartile range = 2-7). The commonest cleaning agents causing OA were chloramines (31%), glutaraldehyde (26%) and quaternary ammonium compounds (11%) and frequently implicated industries were healthcare (55%), education (18%) and leisure (8%).

Conclusions

Certain cleaning agents in common usage, such as chlorine-releasing agents, quaternary ammonium compounds and aldehydes, are associated with sensitization and asthma. Their use alters over time, and this is particularly evident in UK healthcare where cleaning and decontamination practice and policy have changed. Vigilance for OA in workplaces such as hospitals, nursing homes, leisure centres and swimming pools, where these cleaning agents are regularly used, is therefore essential.

Praćenje vršnog ekspiratornog protoka u dijagnozi profesionalne astme

Prema podacima iz Registra profesionalnih bolesti Hrvatskoga zavoda za zaštitu zdravlja i sigurnost na radu, u posljednjih deset godina (2008. ‒ 2017.) prijavljeno je samo 20 slučajeva profesionalne astme od ukupno 2234 prijavljene profesionalne bolesti. To upućuje na značajne nedostatke u prepoznavanju toga poremećaja u našoj radnoj populaciji. Cilj ovoga rada bio je opisati standardnu metodu praćenja vršnog ekspiratornog protoka zraka (eng. peak expiratory flow, PEF) i predložiti praktičnu smjernicu za korištenje te dijagnostičke metode u ambulantama medicine rada i sporta. Praćenje vršnog ekspiratornog protoka zraka (PEF-monitoring) jednostavna je, jeftina, neinvazivna i pouzdana metoda za utvrđivanje funkcije dišnog sustava u stvarnim uvjetima rada i radnog okoliša. Sadašnje smjernice preporučuju PEF-monitoring kao inicijalnu dijagnostičku metodu prilikom sumnje na profesionalnu astmu. Pozitivan test upozorava na povezanost promjene plućne funkcije s radnom izloženošću i važan je dio dijagnostičkoga procesa utvrđivanja profesionalne astme. Najveći je nedostatak te metode da se tim testom ne može utvrditi uzrok astme, tj. on ne razlikuje profesionalnu astmu od astme pogoršane na radu, nema standardizirane metode za interpretaciju rezultata, a mjerenja provode sami radnici pa su moguće namjerne i nenamjerne manipulacije rezultatima mjerenja. U radu je predložena praktična smjernica za primjenu te metode u ambulantama medicine rada i sporta, s preporukama protokola mjerenja PEF-a, prikaza rezultata mjerenja i njihove interpretacije u sklopu dijagnosticiranja profesionalne astme.

Do laboratory challenge tests for occupational asthma represent what happens in the workplace?

Specific inhalation challenge (SIC) is the diagnostic reference standard for occupational asthma; however, a positive test cannot be considered truly significant unless it can be reproduced by usual work exposures. We have compared the timing and responses during SIC in hospital to Oasys analysis of serial peak expiratory flow (PEF) during usual work exposures.All workers with a positive SIC to occupational agents between 2006 and 2015 were asked to measure PEF every 2 h from waking to sleeping for 4 weeks during usual occupational exposures. Responses were compared between the laboratory challenge and the real-world exposures at work.All 53 workers with positive SIC were included. 49 out of 53 had records suitable for Oasys analysis, 14 required more than one attempt and all confirmed occupational work-related changes in PEF. Immediate SIC reactors and deterioration within the first 2 h of starting work were significantly correlated with early recovery, and late SIC reactors and a delayed start to workplace deterioration were significantly correlated with delayed recovery. Dual SIC reactions had features of immediate or late SIC reactions at work rather than dual reactions.The concordance of timings of reactions during SIC and at work provides further validation for the clinical significance of each test.

Occupational asthma caused by acrylic compounds from SHIELD surveillance (1989-2014)

Background

Acrylic monomers (acrylates), methacrylates and cyanoacrylates all cause asthma by respiratory sensitization. Occupational inhalation exposures occur across a variety of industries including health care and dental work, beauty, laboratory science, assembly and plastic moulding.

Aims

To examine notifications of occupational asthma caused by acrylic compounds from a UK-based regional surveillance scheme, in order to highlight prevalent exposures and trends in presentation.

Methods

Retrospective review of all cases reported to the SHIELD surveillance scheme for occupational asthma, West Midlands, UK between 1989 and 2014. Patient data were gathered on demographics, employment, asthma symptoms and diagnostic investigations including serum immunological testing, serial peak flow analysis and specific inhalation challenge tests. Descriptive statistics were used to illustrate worker characteristics and evidence for sensitization to acrylic compounds.

Results

There were 20 affected patients out of 1790 total cases of occupational asthma (1%); all cases were confirmed by OASYS (Occupational Asthma SYStem) analysis of serial peak flow measurements, with three additional positive specific inhalation challenge tests. Three out of 20 (15%) patients were current smokers and 11/20 (55%) were atopic. A variety of exposures and industries were implicated including: manufacturing, health care, beauty and printing and a novel presentation seen in teachers exposed to floor adhesives.

Conclusions

This is the largest reported series of occupational asthma caused by acrylic compounds, which remain an important aetiological factor in this disease. Exposure occurs in a variety of industries, particularly in manufacturing and is seen with other, perhaps better recognized sensitizing agents such as isocyanates and epoxy resins.

Review of Diagnostic Challenges in Occupational Asthma

PURPOSE OF REVIEW

Occupational asthma (OA) is one of the most frequent occupational diseases and its diagnosis is often difficult. This review summarizes its current diagnostic challenges.

RECENT FINDINGS

OA is associated with significant health and socio-economic burden. It is underdiagnosed and physicians need to adopt a stepwise approach to confirm the diagnosis. Although early removal from exposure to the offending agent is associated with a better prognosis, physicians should try to confirm the diagnosis of work-related asthma before taking a worker off work. A proper occupational and medical history is very important but is not enough to make the diagnosis of OA. Objective evidence of work-related asthma is required and this represents a serious challenge to most physicians. Measurement of non-specific bronchial responsiveness (NSBR) and spirometry may confirm the diagnosis of asthma but do not confirm the diagnosis of OA. Serial monitoring of peak expiratory flows (PEF), NSBR, and airway inflammation at and off work may confirm the diagnosis of OA but are often difficult to perform. Confirming sensitization by skin prick tests or specific IgE may help to support the diagnosis of OA. Specific inhalation challenges (SIC) in the lab or at work are considered the reference standard but are of limited access. Medical surveillance programs along with primary prevention (reducing exposure) may help to reduce the burden of OA, but the ideal program has yet to be defined. The diagnostic workup of OA remains a challenge and needs a rigorous stepwise evaluation.

Assessment of work-related asthma prevalence, control and severity: protocol of a field study

Background

There are still uncertainties regarding the respective prevalence, diagnosis and management of occupational asthma (OA) and work-exacerbated asthma (WEA). There is as yet no standardized methodology to differentiate their diagnosis. A proper management of both OA and WEA requires tools for a good phenotyping in terms of control, severity and quality of life in order to propose case-specific therapeutical and preventive measures. Moreover, there is a lack of knowledge concerning their actual costs.

Methods

This project aims at comparing 3 groups of asthmatic subjects at work: subjects with OA, with WEA, and with non-work-related asthma (NWRA) in terms of control, severity and quality of life on the one hand, and estimating the prevalence of OA, WEA and NWRA in active workers and the economic costs of OA and WEA, on the other hand. Control will be assessed using the Asthma Control Test questionnaire and the daily Peak Exploratory Flow variability, severity from the treatment level, and quality of life using the Asthma Quality of Life Questionnaire. A first step will be to apply a standardized diagnosis procedure of WEA and OA. This study includes an epidemiological part in occupational health services by volunteering occupational physicians, and a clinical case-study based on potentially asthmatic subjects referred to ten participating University Hospital Occupational Diseases Departments (UHODD) because of a suspected WRA. The subjects’ characterization with respect to OA and WEA is organized in three steps. In Step 1 (epidemiological part), occupational physicians screen for potentially actively asthmatics through a questionnaire given to workers seen in mandatory medical visit. In step 2 (both parts), the subjects with a suspicion of work-related respiratory symptoms answer a detailed questionnaire and perform a two-week OASYS protocol enabling us, using a specifically developed algorithm, to classify them into probably NWRA, suspected OA, suspected WEA. The two latter groups are referred to UHODD for a final harmonized diagnosis (step 3). Finally, direct and indirect disease-related costs during the year preceding the diagnosis will be explored among WRA cases, as well as these costs and the intangible costs, during the year following the diagnosis.

Discussion

This project is an attempt to obtain a global picture of occupational asthma in France thanks to a multidisciplinary approach.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-016-3824-0) contains supplementary material, which is available to authorized users.

Can serial PEF measurements separate occupational asthma from allergic alveolitis?

BACKGROUND

Occupational asthma commonly results in work-related changes in serial peak expiratory flow (PEF) measurements. Whether alveolitis can result in similar changes is unknown.

AIMS

To identify differences and similarities of serial PEF between workers with occupational alveolitis and asthma seen during an outbreak investigation in a factory with metal-working fluid exposure.

METHODS

Workers with respiratory symptoms and rest-day improvement were identified by questionnaire. Each was asked to measure PEF 8 times daily for 4 weeks at home and work. Alveolitis was subsequently diagnosed from a validated scoring system including radiological changes, carbon monoxide diffusing capacity, bronchoalveolar lavage and biopsy results. Occupational asthma was confirmed with a positive Oasys score >2.5 and a mean rest-work PEF >16 l/min from serial 2-hourly PEF measurements. The Oasys PEF plotter calculated differences between rest and workdays for mean PEF, diurnal variation and the scores were used to confirm an occupational effect (Oasys, area between curve and time point). Records were compared between the alveolitis group and the group with occupational asthma without alveolitis.

RESULTS

Forty workers with occupational asthma and 16 with alveolitis had indistinguishable PEF changes on workdays in terms of magnitude (median reduction 18.5 and 16.1 l/min, respectively) and diurnal variation. Immediate reactions were more common with occupational asthma and late reactions more common with alveolitis.

CONCLUSIONS

PEF responses to metal-working fluid aerosols do not distinguish occupational asthma from alveolitis except in timing. They can be used to identify the workplace as the cause of asthma and also alveolitis.

Cobalt asthma in metalworkers from an automotive engine valve manufacturer

BACKGROUND

Cobalt asthma has previously been described in cobalt production workers, diamond polishers and glassware manufacturers.

AIMS

To describe a case series of occupational asthma (OA) due to cobalt, identified at the Birmingham Heartlands Occupational Lung Disease Unit, West Midlands, UK.

METHODS

Cases of cobalt asthma from a West Midlands' manufacturer of automotive engine valves, diagnosed between 1996 and 2005, were identified from the SHIELD database of OA. Case note data on demographics, employment status, asthma symptoms and diagnostic tests, including spirometry, peak expiratory flow (PEF) measurements, skin prick testing (SPT) and specific inhalational challenge (SIC) tests to cobalt chloride, were gathered, and descriptive statistics used to illustrate the data.

RESULTS

The natural history of presentations has been described in detail, as well as a case study of one of the affected workers. Fourteen metalworkers (86% male; mean age 44.9 years) were diagnosed with cobalt asthma between 1996 and 2005. Workers were principally stellite grinders, stellite welders or machine setter-operators. All workers had positive Occupational Asthma SYStem analyses of serial PEF measurements, and sensitization to cobalt chloride was demonstrated in nine workers, by SPT or SIC.

CONCLUSIONS

We have described a series of 14 workers with cobalt asthma from the automotive manufacturing industry, with objective evidence for sensitization. Health care workers should remain vigilant for cobalt asthma in the automotive manufacturing industry.

Current topics in occupational asthma

The study of occupational asthma (OA) provides insights into asthma in general, as the cause is known. The relationships between the cause and response can be measured and modifying factors can be identified and their influence quantified. Developing OA has much more serious consequences for the patient than new onset asthma unrelated to work exposures, as the patient's livelihood is nearly always affected. Many healthcare professionals are more ready to accept and act on asthmatic symptoms when they are unrelated to work than when work may be the cause; antagonism can also occur in the workplace. This article reviews some of the areas where development and controversy enrich the study of OA. It makes no attempt to be comprehensive.

Work-related peak flow and asthma symptoms in a damp building

BACKGROUND

Working in damp conditions is associated with asthma, but few studies have used objective testing to document work-related patterns.

AIMS

To describe the relationship of peak flow measurements to work-related asthma (WRA) symptoms and WRA among occupants in a damp office building.

METHODS

At the beginning of the study, all workers were offered a questionnaire and methacholine challenge testing. Participants were then instructed to perform serial spirometry using handheld spirometers five times per day over a 3 week period. Peak flow data were analysed using OASYS-2 software. We calculated the area between the curves (ABC score) using hours from waking. We considered a score >5.6 L/min/h to be indicative of a work-related pattern.

RESULTS

All 24 employees participated in the questionnaire. Seven participants (29%) reported physician-diagnosed asthma with onset after starting work in the building. Almost two-thirds (63%) of participants reported at least one lower respiratory symptom (LRS) occurring one or more times per week in the last 4 weeks. Twenty-two (92%) consented to participate in serial spirometry. Fourteen participants had adequate quality of serial spirometry, five of whom had ABC scores >5.6, ranging from 5.9-23.0. Of these five, two had airways responsiveness, three had current post-hire onset physician-diagnosed asthma and four reported work-related LRS.

CONCLUSIONS

We found evidence of work-related changes in serial peak flows among some occupants of an office building with a history of dampness. Serial peak flows may be a useful measure to determine WRA in office settings.

Diagnosis of occupational asthma: an update

Work-related asthma (WRA) includes patients with sensitizer- and/or irritant-induced asthma in the workplace, as well as patients with preexisting asthma that is worsened by work factors. WRA is underdiagnosed; thus, the diagnosis is critical to prevent disease progression and its potential for morbidity and mortality. The interview is the first diagnostic tool to be used by physicians, and the question, "Does asthma improve away from work?" is of the highest sensitivity. However, history can show numerous false positives, and the relationships between asthma worsening and work should be confirmed by objective methods such as peak expiratory flow (PEF) at and away from work. PEF sensitivity and specificity can be enhanced in combination with nonspecific bronchial hyperresponsiveness to histamine/methacholine (NSBP) before and after 2 weeks at work and a similar period off work. Immunologic testing, especially skin prick test (SPT) or specific IgE, is useful for high molecular weight allergens and some low molecular weight agents. Other immunologic tests, as well as induced sputum, measurement of exhaled nitric oxide, exhaled breath condensate, and specific inhalation challenge (SIC) are methods that contribute to the diagnosis and are typically performed at specialized facilities. A diagnosis of occupational asthma (OA) should no longer be based on a compatible history only but should be confirmed by means of objective testing. SIC is the diagnostic gold standard. When SIC is not available, the combination of PEF measurement, NSBP test , a specific SPT, or specific IgE may be an appropriate alternative in diagnosing OA.

An outbreak of occupational asthma due to chromium and cobalt

BACKGROUND

Five metal turners employed by an aerospace manufacturer presented to the Birmingham Chest Clinic occupational lung disease unit. Four cases of occupational asthma (OA) due to chromium salt (3) and cobalt (1) were diagnosed by serial peak-expiratory flow measurements and specific inhalation challenge testing.

AIMS

To measure the extent of the outbreak and to provide epidemiological data to ascertain the aetiology.

METHODS

Participants answered a detailed, self-administered questionnaire, designed to detect occupational lung disease. Urine chromium and cobalt excretion, spirometry and exhaled nitric oxide measurements were taken. Those with possible, probable or definite non-OA or OA, after questionnaire, were invited to undertake two-hourly peak flow measurements and received specialist follow-up.

RESULTS

A total of 62 workers (95% of workforce) participated. Sixty-one per cent of employees were working in higher metalworking fluid (MWF) exposure areas. Ninety per cent of workers had urinary chromium excretion indicating occupational exposure. Sixty-six per cent of workers reported active respiratory symptoms, although there were no significant differences between exposure groups. Two further workers with probable OA were identified and had significantly higher urinary chromium and cobalt concentration than asymptomatic controls. Eighteen cases of occupational rhinitis (OR) were identified, with significantly raised urinary chromium concentration compared with asymptomatic controls.

CONCLUSIONS

Chromium salt and cobalt can be responsible for OA and OR in workers exposed to MWF aerosols. Onset of symptoms in those with positive specific challenges followed change in MWF brand. Workers with OA had increased urinary concentrations of chromium and cobalt, and those with OR had increased urinary concentrations of chromium.

The current diagnostic role of the specific occupational laboratory challenge test

PURPOSE OF REVIEW

Classically, the specific occupational challenge test has been considered as the reference test in the diagnosis of occupational asthma. The present study assesses the usefulness of this test for diagnosing this disease and compares it with other diagnostic methods.

RECENT FINDINGS

Occupational asthma is the most frequent work-related respiratory disease in developed countries. Its correct diagnosis is vitally important not only from the medical point of view, but also in view of the disease's major socio-economic repercussions both for the patient and for society as a whole. Diagnosis is based on clinical suspicion of bronchial asthma and of a possible association with the patient's occupation. Various diagnostic strategies have been proposed, including clinical history, immunological test, spirometry, the study of peak flow, the methacholine test and the specific occupational challenge test, as well as studies of bronchial inflammation using noninvasive methods.

SUMMARY

The specific occupational challenge test remains the reference test for the diagnosis of occupational asthma for causal agents of both high and low molecular weight.

Shift work effects on serial PEF measurements for occupational asthma

BACKGROUND

Diurnal variation (DV) affects lung function but the changes are thought to be related to sleep patterns rather than time of day. When diagnosing occupational asthma (OA), serial peak expiratory flow (PEF) measurements are the recommended first line investigation, but could be confounded by shift work.

AIMS

The aim of the study was to investigate the effects of shift work on PEF measurements used for diagnosing OA.

METHODS

PEF records containing more than one shift pattern with ≥ 4 days per shift were identified. OA diagnosis was based on an Oasys-2 score ≥ 2.51 and non-OA on having an alternative clinical diagnosis and Oasys-2 score <2.51. The mean area between curves (ABC) score, mean PEF DV and cross-shift PEF changes were calculated for each shift.

RESULTS

Records from 123 workers with OA and 69 without OA satisfied inclusion criteria. In the OA group, PEF declined more on afternoon and night shifts than days (P < 0.001). The ABC score was lower in the OA group on night (P < 0.05) and afternoon shifts (P < 0.05) as compared with days, without significant differences in DV. Among those without OA, cross-shift PEF increased more on day shifts (mean + 25 l/min) than afternoon or night shifts (+1 l/min) (P < 0.001). The sensitivity for the ABC score and DV were good and similar across shifts, but specificity was reduced using DV (DV mean 39%; ABC 98%).

CONCLUSIONS

PEF responses between work and rest show small differences according to shift type. The ABC score has a high sensitivity and specificity for all shifts; differences in DV have lower specificity.

Utility of exhaled breath condensate pH for diagnosing occupational asthma

INTRODUCTION

The current reference standard method for diagnosing occupational asthma (OA) is specific inhalation challenge (SIC) with the suspected agent. The alternative method is serial peak expiratory flow (PEF) monitoring. Nevertheless, PEF does not have optimal sensitivity and specificity for this purpose. The aim of this study was to evaluate the utility of exhaled breath condensate (EBC) pH for the diagnosis of OA.

MATERIAL AND METHODS

A prospective study was performed in 37 subjects with suspected OA. Serial PEF monitoring was carried out for 2 weeks at work and for 2 weeks off work. At the end of each period, the EBC pH and the methacholine concentration resulting in a 20% FEV(1) decrease (PC20) were measured. SIC was subsequently performed. PEF graphs were interpreted visually by 3 experienced independent readers.

RESULTS

Seventeen patients tested positive with SIC. Receiver-operating characteristic curves showed that a decrease in EBC pH greater than 0.4 units during the period at work compared to the off-work period achieved the most satisfactory sensitivity (40%, CI 19.4-66.5) and specificity (90%, CI 66.9-98.2) for diagnosing OA. When EBC pH findings were added to PEF results, the diagnostic yield of PEF generally increased. Other test combinations (e.g. EBC pH plus PC20 or EBC pH plus PC20 plus PEF) did not improve diagnostic performance.

CONCLUSIONS

Acidification of EBC pH at work and adding the EBC pH measurement to PEF monitoring during periods at work and off work may be useful for improving the diagnosis of OA.

Clinical assessment of occupational asthma and its differential diagnosis

Occupational asthma (OA) is defined as asthma caused by sources and conditions attributable to a particular occupational environment and not to stimuli encountered outside the workplace. Two types of OA are distinguished based on their appearance after a latency period or not. The most frequent type appears after a latency period leading to sensitization; the clinical assessment of this type of OA is the topic of this review. The differential diagnosis of OA is also reviewed, including work-exacerbated asthma, eosinophilic bronchitis, hyperventilation syndrome, vocal cord dysfunction, bronchiolitis, and other causes of dyspnea or cough.

Sensitization and irritant-induced occupational asthma with latency are clinically indistinguishable

BACKGROUND

Acute irritant exposures at work are well-recognized causes of asthma. In the occupational setting, low-dose exposure to the same agent does not provoke asthma. Occupational asthma (OA) with latency due to irritants is not widely accepted.

AIMS

To compare workers with OA with latency likely to be due to irritant exposures with workers with the more usual sensitization-induced OA.

METHODS

Following identification of a worker who fulfils all the criteria for irritant-induced OA with latency whose investigation documented lime dust as a cause for his OA, we searched the Shield reporting scheme database between 1989 and 2010 for entries where the OA was more likely to be due to irritant than allergic mechanisms and compared these with the remainder where allergic mechanisms were likely. Outcome measures were latent interval from first exposure to first work-related symptom, non-specific bronchial reactivity, smoking, atopy and the presence of pre-existing asthma.

RESULTS

A previously fit lecturer teaching bricklaying had irritant-induced OA with latency without unusual exposures with an immediate asthmatic reaction following exposure to a sand/lime mixture (pH 8). The Shield database identified 127 workers with likely irritant-induced asthma with latency and 1646 with hypersensitivity-induced OA. The two groups were indistinguishable in terms of pre-existing asthma, atopy, age, latent interval, non-specific reactivity and smoking.

CONCLUSIONS

Irritant exposure is a cause of OA with latency currently clinically indistinguishable from OA due to sensitization.

Occupational asthma and rhinitis due to detergent enzymes in healthcare

BACKGROUND

The use of proteolytic enzymes to improve the cleaning efficacy of washing powders was introduced in the mid 1960s. Many microbial enzymes are known to be potent respiratory sensitizers but previously there has been only one case of occupational asthma associated with workplace exposure in a healthcare worker.

AIMS

To report two cases of occupational asthma associated with exposure to biological enzymes in health-care workers and related occupational cases.

METHODS

Reporting of clinical case reports from three different work places.

RESULTS

One case of occupational asthma and three other cases with work-related asthma or rhinitis occurred in one workplace. A single case of probable occupational asthma presented at a second workplace with another case of work-related asthma at a third workplace. Exposures occurred in areas used for cleaning medical instruments and endoscopy suites. Hygiene measurements confirmed the potential for exposure. Control measures were not in place and recognition of the hazard was missing in these workplaces.

CONCLUSIONS

Detergent enzymes when used in healthcare settings should be recognized as potential respiratory sensitizers. Healthcare institutions and professional bodies that recommend the use of detergent enzymes should review their risk assessments to ensure that the most appropriate methods for preventing or reducing exposure are in place.

Differentiating occupational asthmatics from non-occupational asthmatics and irritant-exposed workers

BACKGROUND

Serial peak expiratory flow (PEF) records have been recommended as a first-line investigation in workers suspected as having occupational asthma (OA).

AIMS

To determine which PEF variability index best differentiates workers with OA from non-occupational asthmatics and unaffected irritant-exposed workers.

METHODS

PEF was measured at least four times daily for at least 3 weeks in three groups of subjects: (i) forty healthy grain-exposed farmers and dockers, (ii) forty-two consecutive workers with independently confirmed OA and (iii) forty-eight non-occupational asthmatics. Indices of PEF variability were compared between groups.

RESULTS

The difference in mean PEF between rest and work periods best separated the occupational asthmatic workers from the others. The upper 95% confidence limit of this index for grain-exposed workers was 2.8% of predicted PEF (16 l/min) and 3.3% (15 l/min) for non-occupational asthmatics. Sensitivity for diagnosing OA using this index was 70%. An increase in diurnal variation on workdays of >7% had a sensitivity of only 27% for the diagnosis of OA. The difference between maximum PEF on workdays and minimum PEF on rest days had a sensitivity of <10% against non-occupational asthmatic controls.

CONCLUSIONS

Difference in mean PEF between workdays and rest days is the best simple index for differentiating subjects with OA from those with non-OA or irritant-exposed healthy subjects. Differences >16 l/min are unlikely to be due to significant irritant exposure in healthy workers.

Diesel exhaust causing low-dose irritant asthma with latency?

BACKGROUND

Diesel exhaust exposure may cause acute irritant-induced asthma and potentiate allergen-induced asthma. There are no previous reports of occupational asthma due to diesel exhaust.

AIMS

To describe occupational asthma with latency in workers exposed to diesel exhaust in bus garages.

METHODS

The Shield database of occupational asthma notifications in the West Midlands, UK, was searched between 1990 and 2006 for workers where diesel exhaust exposure was thought to be the cause of the occupational asthma. Those without other confounding exposures whose occupational asthma was validated by serial peak expiratory flow (PEF) analysis using Oasys software were included.

RESULTS

Fifteen workers were identified with occupational asthma attributed to diesel exhaust. Three had validated new-onset asthma with latency. All worked in bus garages where diesel exhaust exposure was the only likely cause of their occupational asthma. Occupational asthma was confirmed by measures of non-specific reactivity and serial measurements of PEF with Oasys scores of 2.9, 3.73 and 4 (positive score > 2.5).

CONCLUSIONS

The known non-specific irritant effects of diesel exhaust suggest that this is an example of low-dose irritant-induced asthma and that exposures to diesel exhaust in at least some bus garages are at a sufficient level to cause this.

Occupational asthma caused by heated triglycidyl isocyanurate

Six workers exposed as bystanders to heated triglycidyl isocyanurate (TGIC) developed occupational asthma confirmed by serial peak expiratory flow measurement and Oasys analysis. Specific inhalation challenge testing resulted in late or dual asthmatic reactions to heated TGIC in four of four tested and was negative in three control asthmatics. One worker tested only with unheated TGIC had a negative specific challenge test. Heated TGIC can cause occupational asthma from bystander exposure.

Occupational asthma: risk factors, diagnosis and preventive measures

In adulthood, new or recurrent asthma is caused by work in approximately 10% of cases. The term occupational asthma is reserved for those cases arising from respiratory hypersensitivity to a specific workplace agent; in others (work-exacerbated asthma) the mechanism is of nonspecific airway irritation on a background of bronchial hyper-reactivity. Some 300 workplace agents are capable of inducing asthma de novo; fortunately, most cases are attributed to a much smaller number to which exposure occurs in a few high-risk occupations. Exposure level is the most important remediable risk factor; the factors governing individual susceptibility are poorly understood. Diagnosis is generally straightforward. Management is rarely pharmacologic and often difficult since the diagnosis incurs important employment and other social consequences.

Two variants of occupational asthma separable by exhaled breath nitric oxide level

Exhaled nitric oxide (FE(NO)) has been used as a marker of asthmatic inflammation in non-occupational asthma, but some asthmatics have a normal FE(NO). In this study we investigated whether, normal FE(NO) variants have less reactivity in methacholine challenge and smaller peak expiratory flow (PEF) responses than high FE(NO) variants in a group of occupational asthmatics.

METHODS

We measured FE(NO) and PD(20) in methacholine challenge in 60 workers currently exposed to occupational agents, who were referred consecutively to a specialist occupational lung disease clinic and whose serial PEF records confirmed occupational asthma. Bronchial responsiveness (PD(20) in methacholine challenge) and the degree of PEF change to occupational exposures, (measured by calculating diurnal variation and the area between curves score of the serial PEF record in Oasys), were compared between those with normal and raised FE(NO). Potential confounding factors such as smoking, atopy and inhaled corticosteroid use were adjusted for.

RESULTS

There was a significant correlation between FE(NO) and bronchial hyper-responsiveness in methacholine challenge (p = 0.011), after controlling for confounders. Reactivity to methacholine was significantly lower in the normal FE(NO) group compared to the raised FE(NO) group (p = 0.035). The two FE(NO) variants did not differ significantly according to the causal agent, the magnitude of the response in PEF to the asthmagen at work, or diurnal variation.

CONCLUSIONS

Occupational asthma patients present as two different variants based on FE(NO). The group with normal FE(NO) have less reactivity in methacholine challenge, while the PEF changes in relation to work are similar.

Recognition and surveillance of occupational asthma: a preventable illness with missed opportunities

Occupational asthma is common, disabling and costly, and it is often difficult to diagnose. Incidence statistics are consequently unreliable, and there are formidable difficulties in recognizing and managing what should be a preventable illness. The opportunities have largely been missed. The author offers a personal view of what, ideally, should be done--recognizing that at present the ideal is not readily practical. Always consider the possibility of an occupational cause at the time adult-onset asthma is first recognized-the probability of this is of the order 9-15%. Do not prescribe treatment unless this possibility is remote or the asthma is life-threatening. If the possibility is not remote seek immediate advice from a specialized centre, without prescribing masking medication and without curtailing usual work practice. The specialized referral centre should place the accurate measurement of airway responsiveness at the centre of investigatory strategies. A return-to-work study, monitored by serial measurements of airway responsiveness and ventilatory function, provides adequate objective evidence for diagnosis in most cases. When a novel cause is suspected, specific inhalation provocation testing with the particular agent in the specialized centre is desirable. Regular competent surveillance is necessary in high-risk occupational environments; this should include environmental monitoring, the detection of relevant new symptoms, spirometry measurements, serum antibody studies (where available) and a robust protocol for managing inevitable failed attendances.

Peak expiratory flow analysis in workers exposed to detergent enzymes

AIMS

To study serial peak expiratory flow (PEF) responses in a group of symptomatic detergent enzyme-exposed workers.

METHODS

Workers were recruited from a biological detergent formulating and packaging company. Those with occupational asthma symptoms and/or specific IgE to a detergent enzyme were asked to complete 2 hourly PEF measurements for 4 weeks. Outputs from the Oasys program (Oasys score, rest-work score and rest-work difference in diurnal variation) assessed PEF response. These were then related to the levels of sensitization and current occupational exposure to detergent enzymes.

RESULTS

In all, 67/72 workers returned PEF records; 97% were able to return a record with at least four readings per day and 87% at least 3 weeks in length. Of total, 79% (n = 27) of those with a final diagnosis of occupational asthma had peak flow records confirming the disease using Oasys. PEF response was similar in those with high, medium and low levels of exposures and those with negative, low-moderate and high specific IgE levels.

CONCLUSIONS

The Oasys program is a sensitive tool for the diagnosis of detergent enzyme occupational asthma, but the levels of exposure and specific IgE sensitization to enzymes do not affect the magnitude of PEF response in symptomatic workers.

PEF analysis requiring shorter records for occupational asthma diagnosis

BACKGROUND

The Oasys programme plots serial peak expiratory flow (PEF) measurements and produces scores of the likelihood that the recordings demonstrate occupational asthma. We have previously shown that the area between the mean workday and rest day PEF curves [the area between the curves (ABC) score] has a sensitivity of 69% and specificity of 100% when plotted from waking time using a cut-off score of 15 l/min/h.

AIMS

To investigate the minimum data requirements to maintain the sensitivity and specificity of the ABC score.

METHODS

A total of 196 sets of measurements from workers with occupational asthma confirmed by methods other than serial PEFs and 206 records from occupational and non-occupational asthmatics who were not at work at the time of PEF monitoring were analysed according to their mean number of readings per day. Measurements from work and rest days were sequentially removed separately and the ABC score calculated at each reduction. The sensitivity and specificity of the ABC score (using a cut-off of 15 l/min/h) was calculated for each duration.

RESULTS

Two-hourly measurements (approximately 8 readings per day) with eight workdays and three rest days had 68% sensitivity and 91% specificity for occupational asthma diagnosis. As readings decreased to <or=4 readings per day, >or=15 workdays were required to provide a specificity above 90%.

CONCLUSIONS

To be sensitive and specific in the diagnosis of occupational asthma, the ABC score requires 2-hourly PEF measurements on eight workdays and three rest days. This is a short assessment period that should improve patient compliance.

Audit of quality of diagnostic procedures for occupational asthma

BACKGROUND

Previous studies have reported deficiencies in the quality of the diagnosis of occupational asthma. A low quality of diagnostic procedures means that the occupational cause of asthma is less likely to be revealed.

AIMS

To assess the current quality of the diagnosis of occupational asthma before referral to a specialist occupational medicine centre.

METHODS

The quality of diagnostic procedures was assessed by reviewing the files of 150 patients who were referred to the Finnish Institute of Occupational Health in 2003 with a suspicion of an occupational cause of their asthma. The quality indicators used were assessment of workplace exposures, spirometric studies, bronchodilator response, serial workplace measurements of peak expiratory flow (PEF) and the time since first symptoms to the final diagnosis. For each indicator, criteria to differentiate between sufficient and insufficient care were developed.

RESULTS

Exposure assessments, spirometric studies and bronchodilator responses were performed in 92, 87 and 79% of cases in the total study group, respectively. Workplace measurements of PEF had been performed in 51% of the cases, and the quality of measurements was sufficient in 52%. Workplace exposures had been assessed significantly more often in occupational health care than in other health care units. The median time from the beginning of symptoms to the final diagnosis was 3.2 years.

CONCLUSIONS

Although the diagnostic procedures were mostly of sufficient quality, the performance of serial measurements of PEF at the workplace and the time to diagnosis should be substantially improved.

A new diagnostic score for occupational asthma: the area between the curves (ABC score) of peak expiratory flow on days at and away from work

BACKGROUND

Evidence-based guidelines recommend serial measurements of peak expiratory flow (PEF) on days at and away from work as the first step in the objective confirmation of occupational asthma. The aim of this study was to improve the diagnostic value of computer-based PEF analysis by using the program Oasys-2 to calculate a score from the area between the curves (ABC) of PEF on days at and away from work.

METHODS

Mean 2-hourly PEFs were plotted separately for workdays and rest days for 109 workers with occupational asthma and 117 control asthmatics. A score based on the ABC was computed from records containing >or= 4 day shifts, >or= 4 rest days, and >or= 6 readings per day. Patients were randomly classified into two data sets (analysis and test sets). Receiver operator characteristic (ROC) curve analysis determined a cutoff point from set 1 that best identified those with occupational asthma, which was then tested in set 2.

RESULTS

Logistic regression analysis showed that all ABC PEF scores were significant predictors of occupational asthma, with the best being ABC per hour from waking (odds ratio, 11.9 per 10 L/h/min; 95% confidence interval, 10.8 to 13.1). ROC curve analysis showed that a difference of 15 L/min/h provided a high specificity without compromising sensitivity in diagnosing occupational asthma. Analysis of data set 2 confirmed a specificity of 100% and sensitivity of 72%.

CONCLUSION

The ABC PEF score is sensitive and specific for the diagnosis of occupational asthma and can be calculated from a shorter PEF surveillance than is needed for the current Oasys-2 work effect index.

Comparison of Peak Expiratory Flow Variability Between Workers With Work-Exacerbated Asthma and Occupational Asthma

BACKGROUND

Peak expiratory flow (PEF) monitoring is frequently used to diagnose occupational asthma (OA). The variability of PEF between periods at work and away from work has not been described in workers with work-exacerbated asthma (WEA). We sought to assess and compare the diurnal variability of PEF during periods at and away from work between subjects with OA and WEA.

METHODS

Workers referred for work-related asthma underwent PEF monitoring for 2 weeks at and away from work. The diagnostic of OA or WEA was subsequently made according to the respective positivity or negativity of the specific inhalation challenges. PEF mean diurnal variability was calculated during periods at and away from work. PEF graphs were also interpreted using direct visual analysis by five observers and using a computer program (Oasys-2, Expert System ) [available at: http://www.occupationalasthma.com].

RESULTS

Thirty-four subjects were investigated (WEA, n = 15; OA, n = 19). There was a greater variability of PEF at work than away from work in both OA (19.8 +/- 8.7% vs 10.7 +/- 6.3%, p < 0.001) and WEA (14.2 +/- 4.8% vs 10.6 +/- 5.6%, p = 0.02). However, the magnitude of the variability was higher in OA than in WEA (p = 0.02). The visual interpretation of PEF or the Oasys-2 program failed to distinguish WEA from OA.

CONCLUSION

Although workers with OA showed a higher PEF variability than workers with WEA when at work, clinicians were unable to reliably differentiate OA from WEA using the visual interpretation of PEF graphs or the computerized analysis.

Approaches to the diagnosis and management of occupational asthma amongst UK respiratory physicians

This study aimed to assess the approach to the diagnosis and management of occupational asthma amongst general (non-specialist) respiratory consultants in the UK. A random sample of 100 UK general respiratory physicians were invited to participate, and asked to provide information on their diagnostic approach to a case scenario of a patient with possible occupational asthma relating to flour exposure. Participation rates were 42% for the main part of the study. Less than half of consultants specifically reported they would ask whether symptoms improved away from work, and just over a third mentioned examining the patient. All of those interviewed recommended a chest X-ray, and 98% simple spirometry. Eighty-six per cent suggested measurement of serial peak flows, recorded for between 2 and 8 weeks, with measurements taken half-twelve hourly. Less than half advocated a specific flour allergy test, and almost one-quarter (23%) would not perform any immunological test at all. Once a diagnosis of occupational asthma was confirmed, less than two-thirds of those interviewed commented they would recommend some form of exposure reduction, and only 28% specifically stated they would offer compensation advice. The diagnosis of occupational asthma by general respiratory physicians within the UK lacks standardisation, and in some cases falls short of evidence-based best practise.

Clinical investigation of an outbreak of alveolitis and asthma in a car engine manufacturing plant

BACKGROUND

Exposure to metal working fluid (MWF) has been associated with outbreaks of extrinsic allergic alveolitis (EAA) in the USA, with bacterial contamination of MWF being a possible cause, but is uncommon in the UK. Twelve workers developed EAA in a car engine manufacturing plant in the UK, presenting clinically between December 2003 and May 2004. This paper reports the subsequent epidemiological investigation of the whole workforce. The study had three aims: (1) to measure the extent of the outbreak by identifying other workers who may have developed EAA or other work-related respiratory diseases; (2) to provide case detection so that those affected could be treated; and (3) to provide epidemiological data to identify the cause of the outbreak.

METHODS

The outbreak was investigated in a three-phase cross-sectional survey of the workforce. In phase I a respiratory screening questionnaire was completed by 808/836 workers (96.7%) in May 2004. In phase II 481 employees with at least one respiratory symptom on screening and 50 asymptomatic controls were invited for investigation at the factory in June 2004. This included a questionnaire, spirometry and clinical opinion. 454/481 (94.4%) responded and 48/50 (96%) controls. Workers were identified who needed further investigation and serial measurements of peak expiratory flow (PEF). In phase III 162 employees were seen at the Birmingham Occupational Lung Disease clinic. 198 employees returned PEF records, including 141 of the 162 who attended for clinical investigation. Case definitions for diagnoses were agreed.

RESULTS

87 workers (10.4% of the workforce) met case definitions for occupational lung disease, comprising EAA (n = 19), occupational asthma (n = 74) and humidifier fever (n = 7). 12 workers had more than one diagnosis. The peak onset of work-related breathlessness was Spring 2003. The proportion of workers affected was higher for those using MWF from a large sump (27.3%) than for those working all over the manufacturing area (7.9%) (OR = 4.39, p<0.001). Two workers had positive specific provocation tests to the used but not the unused MWF solution.

CONCLUSIONS

Extensive investigation of the outbreak of EAA detected a large number of affected workers, not only with EAA but also occupational asthma. This is the largest reported outbreak in Europe. Mist from used MWF is the likely cause. In workplaces using MWF there is a need to carry out risk assessments, to monitor and maintain fluid quality, to control mist and to carry out respiratory health surveillance.

New insights into occupational asthma

PURPOSE OF REVIEW

To examine recent publications on the types of agents involved in occupational asthma, the mechanisms by which they induce asthma, and how best to evaluate and treat workers suspected of this respiratory condition.

RECENT FINDINGS

High rates of occupational asthma and inhalation accidents were found in workers in crafts and related occupations in the manufacturing industries, and in plant and machine operatives; cleaners and construction workers may also be at risk. Further data support a role for CD4 T cells in low-molecular-weight agent-induced asthma, such as with isocyanates, and neurogenic mechanisms may also be involved. The use of noninvasive measures of airway inflammation in the diagnosis and management of occupational asthma such as sputum eosinophils monitoring is promising, although this is less obvious for exhaled nitric oxide. Finally, the persistence of troublesome asthma even after withdrawal from relevant exposure has been re-emphasized and surveillance programs have been proposed.

SUMMARY

Further data have been gathered on the prevalence of occupational asthma in various working populations, its mechanisms of development, the contribution of noninvasive measures of airway inflammation in the diagnosis and management of this condition, and its management and prevention.

Occupational asthma: an assessment of diagnostic agreement between physicians

OBJECTIVES

To investigate the levels of agreement between expert respiratory physicians when making a diagnosis of occupational asthma.

METHODS

19 cases of possible occupational asthma were identified as part of a larger national observational cohort. A case summary for each case was then circulated to 12 physicians, asking for a percentage likelihood, from the supplied information, that this case represented occupational asthma. The resulting probabilities were then compared between physicians using Spearman's rank correlation and Cohen's kappa coefficients.

RESULTS

Agreement between the 12 physicians for all 19 cases was generally good as assessed by Spearman's rank correlation. For all 66 physician-physician interactions, 45 were found to correlate significantly at the 5% level. The agreement assessed by kappa analysis was more variable, with a median kappa value of 0.26, (range -0.2 to +0.76), although 7 of the physicians agreed significantly (p<0.05) with >or=5 of their colleagues. Only in one case did the responses for probability of occupational asthma all exceed the "on balance" 50% threshold, although 12 of the 19 cases had an interquartile range of probabilities not including 50%, implying "on balance" agreement. The median probability values for each physician (all assessing the identical 19 cases) varied from 20% to 70%. Factors associated with a high probability rating were the presence of a positive serial peak expiratory flow Occupation Asthma SYStem (OASYS)-2 chart, and both the presence of bronchial hyper-reactivity and significant change in reactivity between periods of work and rest.

CONCLUSIONS

Despite the importance of the diagnosis of occupational asthma and reasonable physician agreement, certain variations in diagnostic assessment were seen between UK expert centres when assessing paper cases of possible occupational asthma. Although this may in part reflect the absence of a normal clinical consultation, a more unified national approach to these patients is required.