The Medical Surveillance Programme

Procedure Guidelines

 

Table of Contents

 

PURPOSE.. 3

SCOPE.. 3

OBJECTIVES.. 3

TYPES OF MEDICAL EXAMINATIONS.. 4

Design of the Medical Surveillance Programme. 4

CORE APPROACH TO MEDICAL SURVEILLANCE.. 6

Phase One (“Case Identification”): Objective – “Normal or not” 6

Phase Two (“Case Confirmation”): Objective – “Work related or Not” 7

Phase Three (“Case Management”): Objective: - “Optimal Re-integration” 7

CASE MANAGEMENT. 8

DATA CODING SYSTEM.. 8

The Synergee Coding System.. 9

DETERMINING WORK-RELATEDNESS: 11

ACTION PLAN IF AN OCCUPATIONAL DISEASE IS DISCOVERED: 11

AUDIT REQUIREMENTS.. 12

IMPLEMENTATION PROCEDURE.. 12

Compulsory Pre-Employment Examinations. 12

Compulsory Periodic Examinations. 13

Compulsory Exit Examinations. 13

Special Compulsory Examinations. 14

Offer Of Follow-Up (Post-Employment) Examinations. 14

Appendix 1:       Screening. 15

What Makes Screening A Viable Option?. 16

Appendix 2: Establishing Work-Related Causality. 18

Appendix 3: Flow of a Standard Medical Surveillance Programme. 20


PURPOSE

The purpose of the company’s medical surveillance policy is primarily preventative.

1.      To ensure that employees are fit for and suited to the work they are to do, and meet the inherent health requirements for the relevant occupation.

2.      To ensure that the health of employees is not adversely affected by their work or working environment.

3.      To establish baseline medical information on all employees, especially those exposed to health hazards.

SCOPE

The scope of this Policy includes all employees of the Company in the territory of the Republic of South Africa

OBJECTIVES

The objectives of medical surveillance programme are:

1.      To ensure that the individual’s health status does not place the health of that employee, or of any other employees at increased risk 

·       Employees found to be unsuitably employed are assisted in appropriate steps to either improve their medical status, such that they are able to return to their work, or are assisted in a genuine attempt to seek appropriate alternative occupations.

·       Employees with injuries and illnesses, that render them unable to return to their work, are assisted with rehabilitation and workplace re-integration. Where relevant, these employees may need to attempt suitable alternative placement. Where appropriate, assistance should be given to enable compensation of workers with occupational diseases and/or injury.

2.      To monitor employee’ state of health on a regular basis (periodical examination) so as to detect occupational diseases at an early stage, thereby determining the efficacy of hazard control measures.

·       This early identification process allows interventions (medical or logistic) that have the best likelihood for excellent outcomes.

·       Through the analysis of the medical surveillance data, high-risk areas in need of environmental intervention can be identified.

·       This regular interaction with employees should ensure that they are adequately informed of the risks of their work (education) and the results of all medical examinations.

3.      To establish the employee’s state of heath before starting employment (“Baseline”), and on every occasion where there is transfer to another job during his/her employ with the company, thereby ensuring they meet the inherent requirements of the occupation.

4.      To promote optimal health status of employees through identifying:

·       Treatable medical conditions that may render them temporarily unable to perform their work

·       Chronic illnesses that may have no bearing on their fitness to work, but which threaten their personal long-term health

·       By referring them for remediation.

 

TYPES OF MEDICAL EXAMINATIONS

Medical Surveillance comprises the following types of Medical Examinations:

Routine medical examinations

·         Pre-placement medical examinations

·         Annual medical examinations

·         Termination of service

·         Transfer examination

Other medical examinations

·         Specific - e.g. lead, noise exposure

·         Return to work (post injury or post illness)

·         Disability retirement / insurance

·         Physical fitness, determination of

·         Foreign Travel

 

At the end of the examination, the medical team will provide a certificate for the worker that will make clear whether the worker is:

·         Fit for the job assigned with no restrictions, or

·         Fit for the job assigned with certain restrictions, or

·         Unfit for the job assigned and therefore needs to be reassigned into another job (if available)

 

Design of the Medical Surveillance Programme

Note: The technique used to design of the Medical Surveillance Programmes is described in detail in the SOP for the construction of the “Worker Allocated Surveillance Programmes” (“WASPs”).

This is a complex process but can be summarised as follows:

 

Step1: Determine which employee groups require medical surveillance.

The key determinants of who should be required to unergo medical surveillance are the findings of the Health Risk Assessment, which are recorded in the Occupational Risk Exposure Profiles (“OREPs”). Hence in the first step in the design of the medical surveillance programme, the OREPs are consulted, and the data therein is transferred to the WASPs. This is done as follows:

 

Step 2: Determine which tests are required: TEST SELECTION.

Using the WASPs sheets, and the reference tables in the WASP construction SOP, this step is made relatively painless. The tests comprise combinations of questionnaires, clinical examination and special investigations (x-rays, laboratory tests, audiograms, etc.). It is important that the selected tests carry validity. This is determined by their sensitivity and specificity, and the availability of reliable testing facilities (laboratories and testing equipment (including CXR’s, audiograms, PFT’s, etc.). For further information on Sensitivity and Specificity, page to Appendix 1.

 

Step 3: Determine the required STANDARDS for medical adjudication.

Two types of standard are considered:

  1. The medical standards that must be met to “pass” the examination (“Job Fitness standards”).
  2. The action criteria that must be triggered when biological exposure levels or certain exposure effects are exceeded (“Biological Exposure standards”).

The extensive reference tables in the WASP SOP assist the examining health team in this task. It is not possible to establish every permutation that would constitute a reason for excluding an employee in a policy document. Instead, lists of relevant cautions are flagged in the reference tables, to assist the medical professionals in their adjudication. Usually it is a combination of factors that would result in the exclusion of an employee from a particular occupation.

 

Step 4: Determine the TEST FREQUENCY.

This is determined by the degree of risk to which the employees are faced, and the outcomes of the medicals themselves. The higher the risk, the more frequent the tests. The more adverse the outcomes, the more frequent the tests. Test frequencies usually vary from quarterly to every 5 years, but the most common is annual.

 

Step 5: The ethics of medical testing should be considered, with special regard to:

This is particularly sensitive when test outcomes are computerised, which increases the risk that these results may get into the wrong hands. However, even paper records go astray. It is a temptation to flag records by means of the use of markers on the outside of the medical folders – a practice that should be implemented with caution, as this may constitute a breach of confidentiality (when the “coded” flags are interpreted (correctly, or, worse, incorrectly) by the employees.

(ie: the diabetics could be flagged by means of a pink coloured sticker, the hypertensives by means of a blue one, etc. The employees may interpret a certain sticker as marking those with HIV (correctly or incorrectly), which could spark an industrial relations crisis.

This is regarded as an important part of the medical surveillance programme, as it not only provides employees with the results of their tests, as is their constitutional right, but also allays fears that the company is hiding information deliberately. The feedback may be verbal or written, but the written route is favoured. The Synergee System provides re-written letters that ease the burden of communicating in writing to every employee.

Whilst employee education is not a direct responsibility of the medical team, the annual medical provides an ideal opportunity to provide the employees with a further reminder of the issues which they need to be aware in their occupations, with particular reference to the effective use of their PPE, as well as safe work practices.

 

CORE APPROACH TO MEDICAL SURVEILLANCE

Every Medical Surveillance Programme, regardless of the hazards to which the programme is linked, has a core of three phases.

Phase One (“Case Identification”): Objective – “Normal or not”

The objective here is to screen the target group for signs of work-related adverse health effects or for the presence of exclusion factors. This comprises clinical and laboratory screening tests conducted by appropriately trained personnel using approved equipment (eg. audiometry, lung function testing device, and laboratory equipment) and methods (eg. ATS, NIOSH, etc.). These tests need to be chosen carefully, and should have a high degree of validity. Usually the tests in phase one have a high degree of sensitivity, with a lower order of specificity.

The tests results are captured, then printed and interpreted by an Occupational Medical Practitioner with training in this field. Cases of non-occupational adverse health findings (such as high blood pressure, poor vision, etc.) are excluded from further action, and are offered referral to a medical practitioner (facility) of their choice, for follow-up. Those with adverse health effects thought to be work-related (whether exposure related or a potential exclusion), progress to Phase Two.

Phase Two (“Case Confirmation”): Objective – “Work related or Not”

The objective here is to confirm work-relatedness for those with suspicious adverse health findings during Phase One. The appropriate tests are applied as necessary, and specialist expertise may be enlisted. These tests are usually more specific for the occupational disease being evaluated, in order to confirm the diagnosis, or simply explore the links of causality, to determine work-relatedness.

As with Phase One, those with confirmed work-related abnormalities move on the Phase Three, the rest are referred to their own healthcare providers.

Phase Three (“Case Management”): Objective: - “Optimal Re-integration”

This is the final and most crucial component of the programme. It focuses on those employees with confirmed work-related health problems. The actions in this phase include:

1.    Hazard substitution or elimination

2.    Engineering Solutions (isolation & ventilation)

3.    Administrative Solutions (job rotation, safe work procedures, hazard communication, etc.)

4.    Training and education

5.    Personal Protective Equipment

 

P  Point to Ponder: Statutory Obligations

Case Reporting:

Should an employee be found to be suffering from an occupational disease, it is required that the attending practitioner (nurse or doctor) notify the employee directly, the employer and the local offices Department of Labour (as prescribed by Section 25 in the Occupational Health and Safety Act.

Statutory reporting requires the completion of a large number of documents, and a thorough understanding of the statutory mechanisms that govern these submissions. It is strongly advised that an Occupational Medicine Practitioner with the necessary experience is contracted for this component of the programme.

 

Case Submission:

This comprises further data collection to satisfy the requirements of the Workmen’s Compensation Commissioner, and the submission of a claim.  This includes the completion of the following documents as a minimum:

“Employer’s Report of an Occupational Disease” (WCl 1(e)), by the company

“First Medical Report of an Occupational Disease” (WCl 22), by the attending medical doctor

“Notification of an Occupational Disease” (WCl 14), by the employee

Frequently there are also a number of other (more specific) documents, too detailed to list here.  Sample documents required by the Compensation Commissioner are available from Synergee.

 

 

CASE MANAGEMENT

This is the careful monitoring of affected employees, to ensure they are not lost to follow-up, and that they are ultimately managed in such a manner as to reduce or eliminate risks to their health, or to the health and safety of others. Ideally, this process means a return to optimal function. This may entail medical treatment and rehabilitation, or even a transfer to a more suitable occupation.

The Synergee System provides a tracking mechanism for tracking these employees, by means of codes that indicate the employee is still under evaluation (see next section). Furthermore, fields in the medical surveillance datasets are available for recording referrals to specialists, and their outcomes.

 

DATA CODING SYSTEM

One of the most important components of a medical surveillance programme is the methodology for capturing and analysing the outcomes of the medical tests. The key information required in a data management system includes a capability to analyse:

Outcome Data:

·    Normal versus abnormal

·    The severity of the abnormal findings

·    Test-to-test progression (deterioration or improvement)

·    Compensatable or not

Comparative Data:

·    Trends and clustering

Tracking Data:

·    Programme progress (percentage completion)

·    Missed programme elements (employees may have missed certain tests due to their absence at the time of the screen)

·    Referrals, and the outcomes.

·    Submissions the Compensation Commissioner, and the outcomes.

The Synergee Coding System

In order to enable this, outcomes of the evaluations are categorised according to groups, coded as follows.

Synergee Coding System

A

Findings within normal limits.

B (1-4)

Abnormal findings – Occupational:              (1-4 = Borderline – Mild – Moderate – Severe)

BP (1-4)

Abnormal findings – Occupational, but pre-existing (from prior workplace):  (1-4 = as above)

C (1-4)

Abnormal findings - Non-occupational:      (1-4 = Borderline – Mild – Moderate – Severe)

D (1-4)

Unclear reasons for findings:                         (1-4 = Borderline –Mild – Moderate – Severe)

E

Employee is exempt from the test or examination.

X

This test was missed or skipped for some reason, and is outstanding.

 

Further modifying codes (“modifiers”) are used to indicate two other vital pieces of information:

PROGRESS MODIFIERS

COMPENSATION INDICATORS

+/-3

Change by more than a full category

C

Indicates an occupational disease that meets the requirements for a submission to the Compensation Commissioner

+/-2

Change by a category

NC

Indicates an occupational disease that meets the requirements for a submission to the Compensation Commissioner

+/-1

Change, but still within the same severity category.

 

 

P0

No test-to-test change

 

 

PX

No prior test available (a “Baseline”)

 

 

-

Indicates a test to-test deterioration

 

 

+

Indicates a test to-test - improvement

 

 

 

This coding system provides a useful tool by means of which to examine risk profile the group under evaluation, and is also a ready reference by which to designate appropriate actions by categories.  Given some flexibility for isolated individual cases, a generic follow-up plan for these categories is as follows:

Group

Suggested actions

CAT A,

B1, C1 & D1

Inform employee. Take special note of borderline cases.  Routine follow-up.

CAT B2 (occupational)

Investigate & record as an incident.  Inform employee, management and Department of Labour, as required by Occupational Health and Safety Act. Careful follow-up (6-monthly if necessary).  Consider issuing more effective risk controls (See hierarchy of controls).

CAT B3 (occupational)

As for CATB2. Requires direct attention of the risk control team, with a view to immediate exposure reduction.

CAT B4 (occupational)

As for CATB3.  This may require submission to the Compensation Commissioner for possible award. Provide maximum exposure protection – seriously consider a move to a non-exposed job.

CAT C2, C3 & 4

Inform employee only (not management).  Intensity of follow-up depends upon the severity of the disorder and on-going exposure. (6-monthly if necessary). Refer for ingoing medical management and follow-up as necessary (usually at own cost).

CAT D

The “D” code is the flag that indicates “Case Management in progress”. Make every attempt to define the underlying cause and allocate a code from those above. In borderline or mild cases, careful follow-up may suffice.

 

In this way, there is consistency in the way in which the medical programmes flow and are reported.  Interpretations are more rapid and key performance indicators more transparent.  The procedure, the documentation and the underlying IT data gathering process all knit tightly together to form an integrated system, minimising information loss and optimising efficiency.

The spreadsheets provided by Synergee allow normal numeric data entry too, (actual results of tests), not exclusively the coded outcomes. This is particularly useful for tracking data that is not easily and immediately attributed to work exposure, such as lung function tests, lab tests, etc. The actual values can be recorded, for subsequent analysis.

The analytical tools built into the Synergee spreadsheets enable analysis of the data in many ways. This is by means of sophisticated filters, data sorts and proportionate analysis. The results are depicted numerically and graphically.

 

DETERMINING WORK-RELATEDNESS:

This is the most important task of the case management phase. It is not always easy. A listing of the elements that should be considered when determining whether or not an outcome is work-related are listed in Appendix 2. In practice, it is rare that all of the Bradford-Hill criteria are considered. A summary of the most important criteria would include:

 

ACTION PLAN IF AN OCCUPATIONAL DISEASE IS DISCOVERED:

The following steps should be considered, when an occupational disease is discovered:

Incident Investigation

Risk Control:

Employee Care:

Communication:

 

AUDIT REQUIREMENTS

The Medical Surveillance Programme must be subjected to an audit and evaluation from time to time.

 

IMPLEMENTATION PROCEDURE

Once the medical surveillance programme has been established, the medicals begin. These are usually conducted in a manner which is acceptable to the operational requirements of the workplace as well as to the logistic restrictions placed on the medical team (nurse or doctor availability, whether the tests are conducted by outside providers, etc.).

All examinations will be done according to the prescribed Synergee forms.  Each medical has the following components:

1.    Questionnaire. This includes the employee’s relevant medical and personal history, as well as a past work history. Where necessary, further details may be sought by means of specific questionnaires, such as the Lung function Questionnaire, the Audio Questionnaire, and the Contact Allergy Questionnaire, etc.

2.    Physical examination (including basic side-room investigations, such as urine dipstix), targeting the relevant organs systems as prescribed by the WASP.

3.    Special Investigations (laboratory, radiographic, audiometric and other analytic procedures that must be done for that particular exposure, or to test suitability).

 

Compulsory Pre-Employment Examinations

These examinations should be conducted prior to employment, or at least within the first 14 days of employment. This is prescribed in the Hazardous Chemicals Substances regulations and is regarded as a standard benchmark. The responsibility to ensure that the examination is scheduled within the prescribed time deadline rests with the Human Resources personnel. Preferably, a written new recruit Induction Procedure should be in place, describing these requirements.

These examinations are to be documented on the appropriate company form. Additional investigations over and above the standard examination are required only for certain job categories.

The occupation’s inherent medical requirements should be directed by the relevant “Occupational Risk and Exposure Profile (OREP)”, and recorded in a written document called the “Worker-Allocated Medical Surveillance Programme (WASP)”, which should be available to the examining doctor. For further details regarding the compilation of these documents, refer to the Policy on Health Risk Assessment.

For operating positions, it is critical that a current, relevant OREP form is available to the examining doctor. This is to ensure that appropriate attention is paid to any medical condition relevant to the work requirements, or potential exposure to hazards.

Should the applicant be found to be unfit for employment, it is the ethical responsibility of the Doctor to inform the applicant of the medical reason. In cases where the Doctor is unwilling to divulge the reason to applicant, this should be communicated to the applicant’s own Doctor.

Compulsory Periodic Examinations

These are to be performed at least annually (as prescribed by the schedule established by the Occupational Medicine Practitioner), and are to be documented on the appropriate Synergee “Periodic Medical” form.

The schedule for these examinations and occupation’s inherent medical requirements should be directed by the relevant “Occupational Risk and Exposure Profile (OREP)”, and recorded in a written document called the “Worker-Allocated Medical Surveillance Programme (WASP)”, which should be available to the examining doctor.

The responsibility to ensure that the examination is scheduled within the prescribed time deadline each year is usually shared between the Medical Staff and the unit manager. The medical staff should submit a list of employees who are due for a medical examination during the following month, after which it is the responsibility of the unit manager to ensure that the employees are referred accordingly.

Compulsory Exit Examinations

These are to be performed on employees that leave the services of the company, and who were exposed to recognised hazards. The findings are to be documented on the appropriate Synergee “Exit Medical” form.

These medicals should, within reason, be planned timeously, such as within a week of termination of services. The reason is that unexpected findings may require further actions (such as other tests, or referrals, or even a submission to the Compensation Commissioner, if a compensatable occupational disease is identified). The responsibility to ensure that the examination is scheduled within the prescribed time deadline rests with the Human Resources personnel.

Note that this examination is not necessary if the last periodic medical was conducted within 6 months of the services being terminated.

Special Compulsory Examinations

These are NOT routine examinations but should take place when the need arises, as determined through consultation between Management and the Company Doctor. Their purpose is to ascertain the current health status of an employee or his/her suitability to return to, or to continue with work.

These examinations may take place under the following circumstances.

Offer Of Follow-Up (Post-Employment) Examinations

On the occasion of the medical examination at the termination of employment, the company may offer and recommend continued examinations to the employee, usually with the same frequency. This will only be considered where the employee had been exposed to certain agents that continue to pose a threat to the person’s health, after exposure has ceased. This includes certain hazardous agents, such as asbestos and silica dust.

This offer and recommendation must be recorded in the written documents (reminder card) and handed over to the employee at the termination of his employment.

 

 

Appendix 1: Screening

Screening has been defined as the presumptive identification of unrecognised disease or defect by the application of tests or examinations. It involves the performance of a relatively simple test on a large population to separate from it a subpopulation with a high likelihood of having a treatable disease.

The operational objective of screening is the accurate classification of persons who do or do not have the disease in question. The goal or outcome objective of screening is the reduction of the consequences of the disease by incidence, morbidity or mortality.

Test characteristics to consider.

The following test characteristics should be considered when selecting appropriate tests for medical surveillance (Cochrane and Holland criteria):

·         Simple – both in application and in interpretation.

·         Acceptable – the methods employed should cause minimum discomfort, and avoid clashes with belief systems.

·         Cost-effective – the result should be worth the cost.

·         Precise (repeatable) – the result should be reliable, so that repeat testing of the same sample will produce the same result.

·         Accurate – the results should be a true reflection of the condition being sought.

·         Sensitive - the ability of the test to identify the condition, even if it means including a lot of false positives.

·         Specific - the ability of the test to exclude conditions that are the false positives

The “positive predictive value” of a test is a combination of sensitivity and specificity; it’s a test’s ability to accurately identify what it’s looking for (deafness, blindness, etc.); this means without identifying cases incorrectly (“false positives”), and also without missing any (“false negatives”).  It can be calculated, by multiplying the sensitivity by the specificity. In general, although not an absolute rule, tests with a high degree of sensitivity are best for screening, and tests with a high degree of specificity are best for confirmatory diagnosis.

However, note that some tests have high specificity but poor sensitivity, which means that, whilst the cases identified may be reliably regarded as “positive”, these tests may miss a significant proportion of “positive” cases, due to the poor sensitivity. These are therefore only useful when positive – when the result is negative, one cannot be certain that this is true. A good example is the CDT test for alcohol consumption. When it is positive, it is generally regarded as a reliable marker of excessive alcohol consumption (high specificity). However, a significant proportion of cases are reported by the test as normal, even when circumstantial evidence indicates the contrary (poor sensitivity). To continue with the same example, GGT is often used as a screening test for alcohol consumption, because it is fairly sensitive. However, it must be remembered that its specificity is poor – there are many conditions that give rise to a raised GGT. To overcome this, tests are combined in a “battery”, so that the combination improves the overall positive predictive value of the examination. Hence the combination of a good history, collateral evidence, GGT, MCV and CDT all contribute to improve the combined positive predictive value in establishing the presence of excessive alcohol consumption.

 

What Makes Screening A Viable Option?

The Disease

The diseases being screened for must have serious health consequences in terms of morbidity and mortality.

The natural history of the disease needs to be reasonably well understood.

The disease must be treated more successfully in the screen-detected stage than when symptoms have led to the diagnosis. There is no point in screening for a disease that can be successfully treated after symptoms appear, nor is there any point in screening for an untreatable disease.

The detectable pre-clinical phase of the disease should have a high prevalence among the people screened. Otherwise too few cases will be detected to justify the expense of screening.

The Test

The screening test should designate people with early disease as positive and those without as negative.

Success of a screening programme is at meeting these expectations with sensitivity and specificity. In designing a screening programme one often has to trade between sensitivity and specificity. Sensitivity should necessarily be maximised. One needs to balance the consequences of low sensitivity (missed cases or false negatives) and low specificity (economic, social and psychic costs of false positives).

A useful indicator of the capabilities of the screening test is the positive and negative predictive values.

The test must be acceptable to both the employee and tester. It should be as unpleasant as possible and not have potential hazardous consequences. These characteristics assist in compliance of the programme.

The test must be cost-effective.

 
DISEASE +

DISEASE -

TOTALS:

Screen +

a. (TP)

b. (FN)

a+b

Screen -

c. (FP)

d. (TN)

c+d

TOTALS:

a+c

b+d

a+b+c+d

           

            Sensitivity        =          a/a+c

            Specificity        =          d/b+d

            Positive Predictive Value        =          a/a+b

            Negative Predictive Value       =          d/d+d

Evaluation

Proper choice of outcome measure. For cancer and other chronic conditions the objective should be to reduce mortality.

Problems of comparing survival times of screen detected cases against symptom-detected cases: almost invariably, screen detected cases have a longer survival time. Is this due to the effect of screening or the following biases?

·           Lead time bias: screening has advanced the diagnosis of the disease

·           Selection bias: screening may tend to select cases destined to have a benign clinical course. One will detect those diseases with the longest detectable pre-clinical phase. These lesions tend to also have long clinical phases.

Thus people with relatively benign lesions and correspondingly good survival tend to be over-represented among cases detected by screening.

The only valid outcome variable for assessment of the results of a screening programme is the mortality rate from the disease in the total population offered screening in comparison with the mortality rate that would be expected in the same population if screening had not been offered.

Screening should only be done if there is conclusive evidence that the natural history of the disease will be altered in a significant proportion of people screened.

Monitoring

Monitoring is the repetitive performance of an observation or measurement used to detect an unfavourable trend, which may be altered by appropriate intervention.

Screening by definition is cross-sectional and monitoring longitudinal.

 

Appendix 2: Establishing Work-Related Causality

Occupational Health professionals will, from time to time, be required to make a judgement call regarding a putative exposure and an adverse health outcome and the question which arises is whether or not the exposure really caused the disease. Some times this is simpler than in others such as where a very close relationship exists between an adverse health outcome and a particular exposure eg. mesothelioma and asbestos dust exposure. However, do we establish this with entities for which many possible explanations exist such as anaemia, asthma, dermatitis and other target organ effects such as hepatitis, neuritis etc. the answer does not lie solely in statistics but also in applying a certain degree of logic common sense. The Bradford Hill criteria for assessing causality were established to attempt to address this very issue. These are listed as follows:

1                                Strength of association

2                                Consistency

3                                Specificity

4                                Appropriate time relationships

5                                Biological gradient

6                                Biological plausibility

7                                Experimental support

8                                Analogy

9                                Coherence of the evidence

For ease of committing this to memory a suggested acronym is aggaccept, a= strength of association, g = biological gradient, a = analogy, c for consistency, c for coherence, e for experimental evidence, p for plausibility, t for time relationships.

 

So what do all these entities mean?

1                                Strength of an association is generally measured in epidemiology by estimates of relative risk (RR). By convention a RR of greater than 2, points to the existence of a real relationship that does not occur due to chance alone.

2                                Consistency: This term refers to the degree to which a finding can be reproduced in other situations such as different countries, different times and different work situations.

3                                Specificity: This term refers to the theoretical “ideal” requirement that links an adverse health outcome with one specific exposure. The nearest example to this would be the relationship between asbestos and mesothelioma which, although very strong, is nevertheless not 100% specific.  Specificity therefore is a theoretical criterion and is never likely to be fully met.

4                                Appropriate time relationships: A proposed cause must precede an effect and the latent period between the earliest exposure and the effect manifestation should be what would be expected on the basis of the known biology of the disease in question.

5                                Biological gradient: This term refers the dose response relationship with which the exposure and the outcome can be linked. Therefore, the likelihood of developing the adverse effect increases with the increased exposure. For example, this is one of the strongest elements of evidence linking lung cancer with tobacco smoking.

6                                Biological plausibility: This term refers to the conformity of the outcome with the existing knowledge of the pathophysiology associated with the exposure in question. Therefore, this requires a detailed knowledge of the toxicology of the agent to which exposure takes place.

7                                Experimental evidence: This term refers to the finding in the laboratory setting which ideally should support the findings in the clinical setting. This would include laboratory tests for carcinogenesis for example. One should bear in mind that the animal model or test tube circumstance is not necessarily true for the human model.

8                                Analogy: This term refers to the evolution of similar adverse health outcomes under similar situations with other related chemicals. For example, in the case of benzene exposures, similar aromatics such as xylene and toluene should have not very different effects profiles.

9                                Coherence of the evidence: This term refers to the coherence of all the elements of these criteria when they are summed up together. The more coherence that is found, the greater the strength of the association. However, notwithstanding this, the final decision is always a judgement call informed by epidemiological and other evidence and consequently retains an element of uncertainty.

 

Appendix 3: Flow of a Standard Medical Surveillance Programme