Guidance

Guidance on evaluating evidence on health risks associated with occupational exposures

Published 15 March 2019

These guidelines have been produced for internal use by the Industrial Injuries Advisory Council (IIAC) and are based on a larger document on systematic reviews, produced for the 3 UK committees:

• committee on carcinogenicity
• committee on mutagenicity
• committee on toxicity

Informal guidance is given on reviewing and reporting of published literature, particularly epidemiological studies, to provide evidence for potential prescription for Industrial Injuries Disablement Benefit (IIDB).

1. Scoping and problem formulation

To prescribe a disease and occupational exposure or circumstance for compensation, the council requires:

• an evidence-based definition of the disease or condition
• evidence that there is a recognised risk to workers from the occupational exposure or circumstance
• estimation of the magnitude of the risk relating to the occupation such that the link between disease and occupation can be established or reasonably presumed in individual cases, such as if there is a doubling of risk
• assessment of the exposures necessary for the development and severity of the disease

Epidemiological studies can provide important evidence for this purpose.

At the start of each evaluation carried out by the council there should be a clear statement of the purpose and aims of the evaluation. The following points could be considered:

• why is a review of epidemiological evidence needed?
• what is the importance of the issue and consequences of council advice?

Given these 2 points, the committee also needs to consider if a formal systematic review is required.

The following points could be considered:

• is speedy advice needed? If so a limited literature search could be carried out and/or use of an existing review
• is qualitative information sufficient to identify health risk, for example by job title, industry, or does the health risk need to be quantified?
• is there another recent review (narrative or systematic) available in the literature or by a reputable body, such as the International Agency for Research on Cancer, World Health Organization, European Food Safety Authority?
  • if yes, can this be used?
  • does the review only need updating or does it need to be redone?
  • is the review missing older literature that could be valuable?
• is there an existing meta-analysis?
  • if yes, should an update be carried out to include more recent literature?
  • if no, should the council carry out a formal meta-analysis (bearing in mind that this can be a lengthy process)

2. Overarching principles

The overarching principles of evaluating evidence on health risks associated with occupational exposures include:

• the methods used, even for a limited literature review, should always be documented
• an established system or guideline should be followed where appropriate (such as for a systematic review) and this should be stated in publications or reports
• the evidence synthesis should be objective and include critical evaluation of the literature
• uncertainty in the findings and the reasons for this should be discussed
• potential conflicts of interest should be considered in the evaluation of the literature

3. Documentation of the literature search

The council must document the:

• purpose of the search, for example, to identify papers published since a certain date or after a past review
• databases searched, such as PubMed
• time period covered by the search, such as March 2015 to March 2017
• search terms
• numbers of papers identified and numbers included in the review
• is there additional information available from ‘grey literature’ and sources not freely available in the public domain?

4. Describing the findings from a review by the council

It’s important to note that:

• a detailed description of the evidence from all the literature may not be necessary for a short review that is needed quickly – key evidence may be sufficient
• for longer reviews, key information from individual studies needs to be summarised and described
• tables should be considered if there are a large number of papers and studies (for example, for each study, include country, date, design, study population size, numbers of cases, control population selection and size, exposure metrics, confounding data and a summary of key findings)
• the council could also consider presenting results in a forest plot giving the risk estimates and confidence intervals for each study reviewed, or presenting results graphically using other appropriate methods
• a narrative assessment of the quality of papers reviewed is needed but this does not necessarily need to involve a scoring system (qualitative or numerical)
• critical evaluation of any potential biases and uncertainties in individual studies should be included
• the overall evaluation of the body of literature includes comparison of the findings across different populations, exposure contexts, data sources and study methods (triangulation)
• data gaps, extrapolations, differences in interpretation across studies can be highlighted
• the papers should be referenced

5. Evaluating an existing systematic review

Note that:

• the council should consider using an established checklist such as MOOSE^{[footnote 1]} for evaluating (systematic) reviews and meta-analyses and this should be referred to in reports
• the findings from (systematic) reviews should be considered taking account of the review methods used including any quality scoring systems used

6. Conducting a systematic review

It should be considered that:

• if it is decided that a formal systematic review of the literature should be carried out by the council or a subcontractor, established guidelines for carrying out and reporting a systematic review should be used
• it is unlikely that the Council will carry out a full meta-analysis due to time and resources restrictions. However, the council could, occasionally, consider updating an already published meta-analysis with results from more recent studies

1. Stroup DF, Berlin JA, Morton SC et al. Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis Of Observational Studies in Epidemiology (MOOSE) group. JAMA 2000;283:2008–12 ↩