VC Moore, AS Robertson, EE McGrath, G Walters and Burge. Occupational Lung Disease Unit, Heartlands Hospital, Bordesley Green East, Birmingham B9 5SS
SHIELD is the Midland Thoracic Society’s Surveillance Scheme for Occupational Asthma for the West Midlands. The scheme, which was set up in January 1989, was established to study the general and specific incidence of occupational asthma within the West Midlands region and Metropolitan County. The rate of reporting increased sharply in 2004, mainly due to a major outbreak, but since then we have seen a steady decrease in reports, although it is now plateauing. We think this is mainly due to a reduction in the number of doctors / clinics at the Birmingham Chest Clinic.
The most common causes in 2012 were Isocyanates (6 cases), followed by Adhesives (7 cases).
Nearly all cases reported in 2012 were by the Birmingham Chest Clinic. We hope to increase the number notified by others this year by using the MTS website to contact notifiers. The most common method for the diagnosis of occupational asthma still remains a history of improvement of symptoms during holidays or periods off work.
The method of reporting to the Shield scheme has now changed and is done via the new version of the Oasys program that works through the internet. For those that use serial peak flows as a method of diagnosis this will greatly improve the ease of reporting. The data collected is all anonymous and so there are some changes in the data that we record, although it is largely similar.
Shield is a joint project between the West Midlands branch of the Society of Occupational Medicine and the Midland Thoracic Society. The scheme, which was set up in January 1989, was established to meet three main objectives. 1) To study the general and specific incidence of occupational asthma within a defined geographic area, 2) To determine proposed mechanisms of asthma (we don't collect this anymore), and 3) to audit diagnostic methods and objectives.
The last report on Shield's progress was written for 2011 and summarised the information gained in that year, to that of previous years, 2010 and 2009. This report aims to update the participants of Shield by summarising the trends found in 2012 compared to those found in 2011 and 2010.
Metal working fluid is known to be a problem in the world of occupational asthma. Howvere, there are a number of agents that could be responsible for those exposed to it. Metal working fluid itself can be a problem, but it is more often what it dissolved in , for example the metals that are being ground or milled. Cobalt is a common problem in metal working fluid. Biocides also pose a hazard, but these are not always added separately, as they can come ready mixed in the metal working fluid itself. We have seen this issue this year, when a change in metal working fluid brought on asthmatic symptoms. On challenge testing it was due to a biocide contained within the metal working fluid named methylene-bis-morpholine. Always check the data sheets thoroughly and put agents through the manchester asthma hazard index. This one came out close to 1 (very likely to be hazardous).
Number of Cases
The number of cases of occupational asthma reported to the Shield scheme is 25 so far. It is difficult to compare notification for each year properly, as the last few years are likely to change, therefore the graph below is only as a guideline.
Figure 1 Number of cases diagnosed with occupational asthma between the years of 1980 and 2012
In the year of 2012, 26 new cases have been reported to the scheme so far. As the data is anonymous we can no longer report the percentage of men and women. 22 (85%) of the new cases had no pre-existing asthma, 7 (27%) were non atopic and 13 (50%) had never smoked.
Reporting Hospital and Physician
The data is now collected anonymously so we are no longer recording the reporting hospital and physician.
Suspected agents at work
In 2012 the most commonly reported agent that workers were exposed to was Isocyanates, and conglomerates (6 cases each). The 2 most common in 2011 were isocyanates and Adhesives (15 and 7 cases respectively). Isocyanates were also the most common in 2010. 389 cases of isocyanate suspected asthma have now been reported to the scheme, the first case being in 1978. Metal working fluid exposed cases are on the increase again with 4 notifications being made in 2012.
The top reported agents in 2012 were as follows.
Employers and Jobs
The employer for a patient is encrypted when sent to the Oasys Internet Database for confidentiality reasons so it is no longer possible to report this. The jobs are still reported but we have found that job descriptions are very specific and there is rarely more than one patient for each type of job so we have stopped reporting these too.
Methods used for diagnosis
The methods used for diagnosis that are documented on the shield form are; 1) Improvement on holiday, 2) Improvement off work, 3) Serial peak flow charts, 4) Specific IgE, 5) Methacholine at work, 6) Methacholine away from work and 7) Specific bronchial provocation tests. 25 cases were documented as improving on holidays. There were 15 specific challenges performed in 2012.
|| % 2012
|Improving on holidays
|Improving off work
|Serial peak flow
|Methacholine at work
|Methacholine away from work
|Specific Bronchial Challenges
Proposed method of asthma
We no longer record the proposed mechanism of asthma.
We no longer record the subsequent history.
A gold standard occupational asthma case is defined by either; 1) Bronchial challenge test, 2) A four fold change in their bronchial reactivity with a good history, or 3) Positive IgE with a good history, and all of these can be accompanied by a good quality PEF record. 7 cases have become gold standards in 2012 so far. The database does not automatically record gold standard cases due to a fourfold change in bronchial reactivity any more, as there are a lot of different methods of measuring bronchial reactivity that all have different units.
BTS Audit Guidelines
The audit recommendations from the BTS Standards of care for occupational asthma (Fishwick D et al. Standards of care for occupational asthma, Thorax, 2008; 63 : 240-250) are now collected through Oasys. This is the second year that we have recorded adherence with the BTS Audit guidelines. The figures below show the percentage done by visit 2 or before. Specific IgE tests are not available for all agents, so this number is artificially low.
|FEV1 / FVC
|Serial Peak Flows
The new version of Oasys is working well and we are now using it to collect data. We are separating out the Shield data into this report. Data from all people using Oasys will now go into the Oasys Usage report, which will have global scope. We hope to colloborate with other surveillance schemes
Occupational asthma remains a serious disease causing much morbidity, and is potentially preventable. The Health and Safety Executive are currently emphasising the need to control occupational asthma