Health evaluations conducted by occupational health professionals can be grouped into four general types: fitness to work, acute care, health surveillance and voluntary periodic health reviews. Acute care is discussed in Chapter 17, the voluntary periodic health review and biological monitoring in Chapter 19. Disability evaluation is a special case of fitness-to-work evaluation and is addressed in the last section of this chapter.
Fitness-to-work examinations are objective assessments of the health of employees in relation to their specific jobs, in order to ensure they can do the job and will not be a hazard to themselves or others. They should always be conducted with reference to the specific job the worker holds or intends to hold. The circumstances that require such examinations occur the time of application or consideration for entry into employment and assignment to a specific job (preplacement), return to work after illness or injury (return to work), with continuing disability, as part of an employee assistance program and where, for a variety of reasons, the employee's personal health and the working conditions become incompatible. Fitness-to-work examinations are required in various circumstances as shown in Talbe 18.1. They must be speficially job-related, with judgments of fitness being based on the principle that the employees' state of health in relation to their individual jobs will not be hazardous to themselves or others. This principle is acknowledged in various human rights codes. These examinations balance the rights and obligations of the employee and employer and must be conducted in a manner consistent with professional codes of ethics. It is preferable that they be undertaken by individuals who are specially trained or well experienced in occupational medicine or occupational health nursing.
Fitness-to-work examinations are requested either at the direction of the employer or voluntarily by the employee. Company-directed examinations occur because company policy or government regulation requires them. In performing these examinations a clear understanding by the health professional, whether physician or nurse, of the working conditions and activities of the specific job is needed. The occupational health professional judges fitness-to-work based upon a medical examination dictated by working requirements. The clinical opinion is reported to the employer in the form of fitness-to-work determinations without using medical terminology or making mention of a diagnosis. Typically the terms used are fit, unfit, and fit subject to work modifications, with the latter two further qualified as temporary or permanent.
The armed forces have devised useful systems that grade physical capability and fitness to serve under various weather conditions and in certain geographical locations. Such systems, however, have little practical use in the civilian work force. Their strengths lie in being able to quickly identify large groups of people with similar capabilities. Workers' compensation boards are capable of providing fairly detailed psychometric and occupational capability assessments. Unfortunately their facilities and personnel are usually over-worked and generally cannot be used for routine or private assessments. Many hospitals have occupational therapists on staff and a few large industries employ them. However, their availability is usually very limited.
At times, it may not be possible or appropriate for the occupational health professional to perform the medical examination personally. In this situation the medical findings and opinions provided by private clinicians or a consultant will be interpreted in light of the working conditions and then rendered into a fitness-to-work determination. If an occupational health professional is not on staff, a company official must provide the private clinician or consultant with a description of the working conditions and job requirements so that as informed a fitness-to-work judgment as possible can be made. It is never appropriate for company personnel, including supervisors and employment office staff, to solicit specific medical findings and diagnoses from private clinicians and consultants.
To be useful to the employee and employer and to be consistent with human-rights legislation, preplacement examinations must be structured so that they are specific to the working conditions and job requirements medically and are timed after a job offer has been made. An employer cannot arbitrarily deny a person a job opportunity on the basis of a physical or emotional disability. However, the job offer can be made contingent upon passing a medical examination that ensures the employee will be able to perform the job and will not be a hazard to him or herself or others while working in that job. The employee will be refused the job only if the health of the employee is not compatible with the working conditions and the working conditions and job requirements cannot reasonably be altered.
Not all companies conduct routine return-to-work examinations. Even so, such examinations are very useful to evaluate workers where there is an unusual duration of absence or following a severe illness or injury. Either premature or unduly delayed return to work may cause both employee and employer difficulties. A relevant and timely examination can reduce over-all lost time for the employee and can improve productivity for the employer. Continuing disability assessments are used when an employee remains absent from work for extended periods or is facing return with a new disability. Help can be provided by providing rehabilitation opportunities, improving therapeutic support of the employee, assisting the private clinicians to manage the case, and working with the company to provide suitably modified work so that a timely return to work can occur.
Employee assistance programs are a potential resource for fitness-to-work evaluations when alcohol and drug abuse are the basis of the medical problem. These referrals are the most sensitive and difficult type of fitness-to-work assessments. This review must be done in complete confidence, and a fitness-to-work judgment would not be revealed to the employer unless it is in the best interests of both the employee and employer and the employee agrees. They usually concern employees who have been directed for a medical review prior to discipline or dismissal for failing job performance. If the employee agrees to a medical review and a valid health reason is found to be the cause of the failing performance, then no discipline or dismissal should follow. If, however, the employee refuses the medical review or if no valid health reason is found, then discipline or dismissal will proceed. A less troublesome version of this type of assessment occurs when it is suggested that the employee undertake a medical review for failing performance but before discipline or dismissal have been considered. In this situation the employee is not obliged to undergo the medical review. Occasionally in company-directed or suggested but voluntary evaluations the employee will request that his or her own physician conduct the medical review. This may be appropriate if the private physician is informed of all the details of the employment situation, is sufficiently experienced to render an informed opinion and is objective enough to render an unbiased evaluation. This is unusual and may be very difficult for a physician caring for the worker's family, especially in a small community. When possible, therefore, a properly trained and informed without a close connection to the family physician ought to make these difficult assessments. Ideally, an employee would seek medical assistance voluntarily before job performance became an issue.
Fitness-to-work examinations are also indicated when an employee's health has changed without time loss or failing job performance, when conditions have changed significantly in the workplace, or when an employee transfers from one job to another where the working conditions are more strenuous or involve significant and different exposures.
Medical examinations to determine fitness to work concentrate on the relation between health and the demands of the job workplace and should not be confused with health surveillance tests for actual or potential exposure to toxic materials for harmful physical agents or with company-sponsored periodic health examinations for the promotion and maintenance of health.
In fitness-to-work examinations the physician is asked to render an informed opinion about a person's health and functional capabilities that will affect the rights and obligations of not only the person but also the employer. With the increasing social awareness of employees, unions and employers, these examinations must be performed with great competence and objectivity; otherwise, the concerned parties will feel unfairly treated and will distrust the outcome of the examination. Furthermore, the physician must bear in mind the doctor-patient relationship, with all the attendant rules of behavior dictated by professional codes of ethics and laws.
This system of matching job requirements to worker's abilities has been developed for a large, highly diversified and sophisticated employer with a wide range of job categories. It is presented as a system that has been successful in practice and has been found convenient to use by human resource dpeartments as well as occupational health and safety departments. It also clearly illustrates the issues of concern to the physician evaluating the fitness-to-work of a candidate for a position.
The job advertisement record procedure (JAR) meets all these needs in a fitness-to-work examination. The JAR (Figure 18.1) brings together two types of information -- the working conditions of a specific job (Section A) and the health standards relevant to those conditions and requirements (Section B). Consideration of this information in relation to the findings on examination and investigation will enable the physician to form a clinical opinion and thus arrive at an objective, ethical judgement of fitness to work at that job (Section C). Figure 18.2 illustrates this process, which can be applied to each of the circumstances listed in Table 18.1.
Four copies of the JAR form are usually distributed: to the employee's medical file, the employee, his or her supervisor and the personnel department. (Further distribution may vary according to the structure and requirements of each organization.) Section B, however, is completed only on the copy destined for the medical file, in order to ensure confidentiality.
The information recorded in this section should accurately and concisely describe both aspects of the working conditions of the job, the environment and the way in which work is performed. A complete, detailed account of every aspect of the job, otherwise known as a job description, is not necessary. Specific information such as hours of work, level of stress, job location, and exposure to potential physical injury, noise, heat and toxic or biologic hazards should be entered. In large organizations this information is typically obtained from the employee presently holding the position, the immediate supervisor, the personnel department, the occupational hygienist, the safety specialist and the medical staff. In smaller organizations, there is usually no difficulty because most long-term employees are knowledgeable about conditions. The details of the working conditions which must be considered are outlined in Table 18.2. An example of section A is found in Figure 18.3a.
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Figure 18.1. The job advertisement record, as developed by the Nova Corporation.
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Figure 18.2. The process of conducting fitness-to-work evaluations requires matching of the working conditions and health standards to the medical findings and clinical opinion following examination.
The health standards are usually determined by the physician, often by or with the help of an occupational health nurse and sometimes with input from the occupational hygienist and safety expert. A framework for developing standards appropriate to specific jobs has been formulated by the County of San Bernardino, California, and is under further development by MED-TOX Health Services of Ontario, California. The military also have rigorous and explicit standards for their billets. The standards are based on the physician's understanding how the body may be affected by the working conditions. If one of the conditions, for example, is that an employee must work for up to 8 hours in isolation operating a motor vehicle, the physician will identify the central nervous system as one body system that should be functioning within acceptable limits. The extent of the physical examination and the laboratory tests needed to characterize the system will be determined by the specific details of the working conditions. In the example given, a thorough examination of the CNS is required, and a seizure disorder requiring medication for control would be a contraindication to assignment to the job. The history, findings at physical examination, test results and clinical opinions are recorded in the usual manner on the employee's medical chart and are treated confidentially. The overall clinical determination is based only on those health standards relevant to the working conditions. The body systems of concern and various screening methods appropriate to their evaluation in regard to working conditions are outlined in Table 18.3. The systems referred to throughout the procedure are: cardiovascular system (CVS), central nervous system (CNS), endocrine (ENDO), gastrointestinal (GI), genitourinary (GU), hearing, hematological (HEMAT), immunological (IMMUN), integumentary (INTEG), mental status, musculoskeletal (MS), respiratory (RESP), and vision.
1 Short Description of the Job Function
1.1 Write a short but precise statement of the job function 1.2 Record percentage of time spent on specific duties (e.g., 50% cleaning and servicing furnaces and air conditioners, 20% snow shovelling and gardening, 30% unloading supplies and moving furniture).
2 Location - record approximate percentage of time in:
2.1 Office/field/lab/computer center/plant/service centre 2.2 Offshore rigs and other isolated locations 2.3 Expatriate (foreign country) 2.4 Indoors/outdoors 2.5 In transit, specify form of transportation
3 Hours of Work
3.1 Shifts: 12 hour, rotating 3.2 Lunch breaks: scheduled, unscheduled 3.3 Overtime: may describe as: excessive (daily and/or weekends), frequent (2-3 times/week), occasional (one time/week), rare (one time/month), periodic (episodic), emergency call out, on call
4 Occupational Safety Hazards
4.1 Safety (Acute Traumatic Injury) 4.1.1 Machinery: specific type of equipment used, working near (within 3 feet) or operating moving or dangerous machinery 4.1.2 Working in tanks and vessels 4.1.3 Working at heights 4.1.4 Walking over rough terrain and or slippery surfaces (more than 3 times/year) 4.1.5 Other 4.2 Ergonomic (Chronic Traumatic Injury) 4.2.1 Lifting, carrying, pushing or pulling - amount of weight (more than 30 lbs.) 4.2.2 Bending, stooping, twisting, pushing and pulling (more than 1 hour/day) 4.2.3 Climbing to heights 4.2.4 Working in awkward positions or cramped quarters. 4.2.5 Standing (more than 2 hours/day) ] record percentage of Walking (more than 1 hour /day) ] time spent at each Sitting (more than 4 hours/day) ] 4.2.6 Using repetitive motions 4.2.7 Using equipment: VDT/word processor (more than 1 hour/day) hand tools 4.2.8 Performing office functions 4.2.9 Other
5 Occupational Health Hazards
5.1 Physical Agents 5.1.1 Thermal: temperature extremes, humidity 5.1.2 Radiation: ionizing, non-ionizing, ultrasound 5.1.3 Noise: continuous (greater than 85 dB),intermittent, impulse 5.1.4 Vibration 5.1.5 Atmospheric pressure 5.1.6 Other 5.2 Chemical Agents List any potential chemical agent exposures 5.3 Biological Agents 5.3.1 Bacteria, molds, fungi 5.3.2 Other
6 Special Requirements
6.1 Operating mobile equipment: driving heavy equipment or trucks, servicing or flying company planes, driving company vehicle 6.2 Participating in offshore survival training and working in an offshore environment 6.3 Participating in fire fighting training 6.4 Responding to emergency situations 6.5 Travel requirements: plane, helicopter 6.6 Special tasks or conditions: requiring colour vision; performing detailed, precise work; working near or directly with food; conducting aerobic fitness classes; working with laboratory chemicals 6.7 Personal protective equipment used 6.8 Isolation (record percentage of time): use geographical statement such as offshore, meter station; working alone
7 Psychosocial Demands
7.1 Level of decision making and responsibility - minimal, moderate, high 7.2 Dealing and working with others 7.3 Workload: intensive, moderately intensive, peaks, steady deadlines to meet, whether critical, frequent, occasional 7.4 Other
This blank page represents Table 18.3
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Figure 18.3a. The section on working conditions of the job advertisement record.
An example of Section B of the JAR as completed for a reasonably demanding job is presented in Figure 18.3b.
The confidential clinical opinion is rendered as a fitness-to-work determination in Section C. There are six possible judgments, the appropriateness of which may depend on the type of fitness-to-work examination being done: fit, temporarily fit, fit subject to work modifications, temporarily fit subject to work modifications, temporarily unfit, and permanently unfit. These are defined below:
Fit: This judgment means that the employee is able to perform the job without danger to self or others, without reservation. The subcategory "temporarily" can be used for all types of medical assessments except preplacement. "Permanently" should never be used with a judgment of "fit" since physicians cannot see into the future.
Fit subject to work modifications: A judgment in this category means that the employee could be a hazard to self or others if employed in the job as described but would be considered fit to do the job if certain working conditions were modified, such as the way the work is performed or the working environment,. The modifications required must be clearly described in the comments section. If they can be accommodated, the employee is considered fit for the modified job. If, they cannot be reasonably accommodated, the employee is deemed temporarily or permanently unfit. "Temporarily" means that if the person's condition improves with time, the requirement for work modifications may be lifted. "Permanently" means that the employee will never be fit for the job without the modifications. In either instance, a follow-up visit must be arranged in case circumstances change and the findings at the follow-up visit must be recorded either in the comments section or on a new JAR. Any employee considered fit subject to work modifications must be fully informed of both the medical findings and the modifications.
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Figure 18.3b. The section on health standards of the job advertisement record.
Unfit: This category describes the employee who is unable to perform the job without being a hazard to self or others. This judgment and the subcategories "temporarily" and "permanently" can be used with any type of fitness-to-work examination. "Temporarily" means that the medical condition may improve with time, thus allowing return to work or transfer to some other job. "Permanently" usually means that the employee will never be fit for the job and that no modification of the working conditions is reasonably possible or medically relevant; if it means that the employee is unable to do any available job, with or without work modifications, a statement to this effect should be made in the comments section.
Any employee who is considered unfit, whether temporarily or permanently, must be fully informed of the medical findings. In the case of a preplacement medical assessment, no follow-up visit is required, as the applicant is clearly unsuitable for the job. Otherwise, a follow-up visit must be arranged in case circumstances change.
The physician arrives at a fitness-to-work judgment by evaluating the information in Sections A and B of the JAR against a clinical opinion based on a relevant medical evaluation. Fitness-to-work judgment must be based on current working conditions and the worker's current health status. Decisions must not be influenced by speculation on what might happen in the future, but they must reflect clinical acumen in detecting signs of incipient conditions. In addition, the reason for the examination and the limitation of the assessment to present findings and conditions must be taken into account before the final determination is made.
The reason for the fitness-to-work evaluation having been conducted in the first place must be absolutely clear to the physician, the employee and the employer. In general, there are three situations in which examinations are conducted. One is at the initiation of the employer, for any of the types of examinations listed in Table 18.2. The most difficult circumstance occurs when job performance is clearly failing, allegedly for health reasons, and the employee risks being disciplined or losing the job. A fitness-to-work examination is required by the employer to find out whether a health problem exists that will cause poor job performance. Here the physician's judgement will have an immediate effect on the person's continued employment. If the person is found fit to work without reservation, the result will probably be discipline or discharge. If, on the other hand, the employee is found to have a health problem that has legitimately affected performance, discipline or discharge will likely not occur. In the second situation a somewhat different approach is taken when performance is not yet failing but there is concern that it may do so. Here a medical examination may be suggested by the employer to clarify whether a correctable health problem is a factor. The employer will not force the examination upon the employee. In both the first and second situations the JAR procedure can be followed.
The third situation, however, is the one in which the employee voluntarily seeks confidential medical advice, and the employer is not officially involved. In this case the JAR procedure is followed only as a guide. Copies of the completed form can be distributed to the personnel department or to supervisors or both if but only if the physician and the employee both consider this action to be in the employee's best interest.
Resolution of cases in which the judgement is "fit subject to work modifications" or "unfit" requires close communications between the personnel department, the supervisor and the health professional. A telephone conversation or meeting may be required to supplement the JAR. Moreover, the physician, armed with a clear knowledge of both the employee's medical status and the working conditions, must be able to provide comprehensive advice to the personnel department and supervisor without using medical terminology or giving a diagnosis. However, the employee (and any person whom the employee may designate by signing a form for the release of medical information) must be fully informed of all the medical findings and the health standards upon which the judgement was made.
In conclusion, if the process of developing specific health standards is based on a clear understanding of actual working conditions, and if the clinical opinion is in turn based on a medical examination that is relevant to those health standards, a proper fitness-to-work judgment can be made. Such a judgment will be viewed as fair and valid not only by the employee and the employer but also by concerned observers, such as union representatives, proponents of human rights, legislators and other health professionals. Finally, the physician will be able to act ethically by protecting the patient's right to confidentiality of medical information, because only the outcome of the process will be revealed -- the fitness-to-work assessment.
Disability evaluation is a special case of fitness-to-work evaluations in which the objective is to determine whether the worker who has sustained an injury or illness is capable of returning to work, if not what alternative work might be suitable, and an estimate of the degree of disability for compensation purposes. There are few valid tests unique to the evaluation of a disability by themselves to help an occupational health professional determine worker's specific ability to work. Traditional clinical examination methods and laboratory tests help the examiner form a clinical opinion but these should be applied selectively. Only those pertinent to the evaluation of a bodily system relevant to the working conditions and requirements of a specific job should be used. For example, if the state of the cardiovascular system is identified as relevant to the safe operation of a large highway transport truck, then a cardiovascular stress test might be used as one of the methods of assessing an employee's fitness for that job following a myocardial infarction. In other cases where the respiratory system is relevant, one might consider the use of special pulmonary function tests such as bronchoprovocation challenge in cases of asthma. Experience has shown, that routine nonselective use of tests is rarely if ever helpful in disability evaluations. Perhaps the laboratory test that has proven to be least useful as a routine test is the back x-ray.
Specific and standardized clinical tests applicable to particular job functions, such as one that could evaluate muscle power and endurance, would be very useful in occupational health evaluations. Much research is needed to develop simple, reliable and relatively inexpensive tests that can evaluate functional capacity, and that can be used to evaluate a wide range of jobs. Until such tests become readily available, whenever possible, occupational health evaluations and the fitness-to-work judgments based upon them ought to be rendered by highly trained and informed occupational health professionals who have a clear understanding of the relevant bodily systems, and who use only those clinical examination methods and laboratory tests that are specific to evaluating these systems.
In occupational medicine, the diagnosis is often the beginning rather than the end of the evaluative process. This is particularly true for occupational illnesses due to workplace exposures and for repetitive motion injuries. The related but distinct questions of the exposure responsible, the work-relatedness of the condition, and the expected degree of disability are sometimes more important than a precise diagnosis because on such questions hinges eligibility for compensation, prognosis for rehabilitation, fitness for future work, and prevention for the protection of other workers.
Contradictory data are common in the presentation of a work-related case. The perfectly consistent case, the patient whose case is characteristic of a disorder in every respect, is decidedly unusual and the subject of clinical judgement. The first step in clinical evaluation, therefore, is to consider the validity of the data at hand.
Clinical data can be validated either externally, by comparison with information collected elsewhere, or internally, by assessing the degree of agreement with other data in the case. External validation is usually provided in a clinical setting in the form of other records from consultants, hospitals, or primary physicians, company personnel or industrial hygiene records, union records, and workers' compensation claims. Hygiene records are often especially useful because they may contain information on the level of exposure sustained by the worker. Unless such external data were gathered for reasons completely unrelated to the case at hand, however, the relative validity of these records may be no greater than the patient's history. It is often dangerous to accept statements in a dictated summary on smoking or other relevant historical statements unless one can find the original record or can find mention of the item in at least two independent sources in which the parties responsible had no contact.
Internal validation of data is often more practical in a clinical setting. One should consider whether the data are reasonably consistent, comparing the stated chief complaint with the review of systems and the findings on physical examination with the patient's own description of the problem. One should be alert to major inconsistencies in the history of the present illness bearing in mind that minor lapses or changes in the history are only human. When contradictions fall beyond the range of usual clinical experience, there are several possible explanations: (1) The patient may be upset or distracted. (2) The patient may not believe that the clinician is taking the problem seriously enough and is exaggerating to get the point across. (3) The patient may be experiencing a true compensation neurosis without intent to deceive and may not realize that the story given is contradictory. (4) The patient may be a poor historian and may simply be in error. (5) The patient may be mentally ill. (6) The patient may be malingering. A covert mental status examination and a few clinical checks for malingering should be included as important parts of every disabililty evaluation. Simple errors in recall and minor inconsistencies in findings tend to be random and relatively trivial. When all of the mistakes point in the same direction, however, there should be a high index of suspicion for voluntary or involuntary distortion of the history.
The most intuitive step in the process is that in which the clinical picture leads to a diagnosis, which in turn will lead to judgments on causation and work-relatedness.
In occupational medicine, complex problems frequently involve several organ systems. Faced with a new and complex case, it is very useful to arrange the patient's complaints and the clinical findings into problems as in the problem-oriented medical record and then to categorize these by organ system. Another useful approach is to think in terms of structure and function. Are changes on the chest film, for example, compatible with the changes on spirometry? The process of arriving at a diagnosis is the essence of a clinician's cognitive skill, and combine deductive logic, intuition, pattern recognition, and judgments on probability. Clinicians derive a diagnosis by pattern recognition, which tends to work most reliably on common problems, and by deduction, which is the way clinicians are "supposed" to work, but which is usually reserved in practice for complex cases. The first pathway, pattern recognition, is the usual way that clinicians arrive at a diagnosis. Nonetheless, a pattern which may be encountered frequently in a common disease may be repeated in an uncommon disease or exposure situation and may mislead the clinician who fails to consider an occupational etiology. For example, some variant forms of occupational asthma resemble intrinsic asthma, and the two forms of fume fever (metal fume fever and polymer fume fever) behave like influenza. Experienced clinicians may err by assuming that a familiar pattern represents a familiar disease. The process of diagnosis is no different in occupational medicine than in any medical practice generally, but often places more of a premium on deduction because of the complexity of many cases.
The deductive pathway to a diagnosis requires sequential testing to rule out alternative diagnoses. The clinician first considers all conditions likely to present the clinical picture and the possibility of other conditions which present in this way only rarely. The list of diagnostic possibilities is the differential diagnosis. The deductive process then proceeds by eliminating the various possibilities by special tests, by observing the clinical course of the disorder or by a therapeutic trial until the correct diagnosis is found. Since most clinical tests are not absolutely specific for a given disease, the deductive process more often involves ruling out conditions because of their incompatibility with the clinical findings than confirming the diagnosis with a specific test. In occupational medicine, the process of deductive reasoning usually begins with a differential diagnosis that includes both occupational and nonoccupational disorders. A relatively common problem of this sort is pulmonary interstitial fibrosis, which may arise from a number of exposures and a wide range of non-occupational causes.
Deductive reasoning in occupational medicine is made easier by the existence of many special toxicologic tests for the detection of toxic substances and their metabolites (such as urinary free benzene and phenol in the case of benzene exposure) and biological monitoring tests for the early detection of physiologic and biochemical changes induced by toxic exposure (such as plasma and red blood cell cholinesterase levels for the organophosphate and carbamate pesticides). Sophisticated special tests are only useful when the occupational exposure is considered in the differential diagnosis, however. Thus, it is extremely important that the index of suspicion for occupationally-related disorders be high. Since the non-specialist cannot be expected to remember the details of the many occupational illnesses, some of which are quite infrequently seen, easy access to authoritative reference works or consultation by telephone is essential.
The difference between a diagnosis and the identification of an etiology is important to understand. A diagnosis implies recognition of a known disease, which may or may not have a known etiology. When a number of etiologic agents or exposures may result in an identical clinical picture but different prognoses, the diagnosis is incomplete without the etiology. In this sense, interstitial fibrosis is not a diagnosis; usual interstitial pneumonia resulting from diffuse alveolor damage from recurrent or chronic exposure to a toxic gas would be a diagnosis without a clear statement of the etiology. The specific toxic gas, such as nitrogen dioxide, would be the etiology.
Causation in occupational medicine implies an understanding of the etiology of the disorder, the circumstances of exposure, and the predisposing conditions of the patient. In the case of a camera repairman with painful lower extremity paresthesias and diminished sensation, the cause may be multifunctional: diabetes, alcohol abuse, and transdermal absorption of mildly neurotoxic solvents. Toxic exposures are not always occupational. In a clear case of lead intoxication, a patient initially presumed to have experienced exposure on the job turned out to have been exposed much more heavily while refurbishing his home, stripping lead-containing paint off the walls of an old house he was renovating.
Causation is the interpretation in a specific case of the most probable direct cause of the disorder. Because the question of causation in an individual case is sometimes possible to prove beyond doubt, particularly in the case of a chronic illness with a long latency period, such as cancer, the clinician must often play the odds by relying on the epidemiologic literature. A plausible statement of causation must specify what the offending agent was, when and where the individual was exposed, and why this particular patient developed the disorder and not another worker in the same workplace.
Identification of causation is a critical setup in an occupationally-related case because it may establish the patient's entitlement under workers' compensation if work-related and may force correction of the problem, if it still exists, to prevent others from being exposed. The resolution of causation leads naturally to the assessment of work-relatedness.
When an employee falls off a ladder while on the job and sprains his foot, work-relatedness is obvious. However, assessing work-relatedness is a difficult matter in many cases of chronic disease or in some contested workers' compensation cases. Many disorders which are known to have occupational causes may also occur for other reasons and for unknown causes. A given case may present with a history of multiple exposures over several jobs each associated with a particular health outcome. This is particularly common in cases of bladder cancer, asthma, hearing impairment, and osteoarthritis. After the diagnosis is established and a presumption of causation is made, three steps are necessary.
The first is to document insofar as documentation is possible that the patient actually sustained the presumed exposure. Consider the case of a worker in a cement factory who admittedly smoked by developed squamous cell bronchogenic carcinoma at only 40 years of age, much ealier than one would expect from smoking alone: the presence of pleural plaques on chest film was convincing evidence that he had been exposed to asbestos, which is added to cement in manufacturing sewer and water pipe.
The second step is to rule out associations having nothing to do with work. Skin rashes, hepatitis, fever, aplastic anemia, purpura, nausea and many other problems which may appear to be work-related may result from medication. Avocational activities, including hobbies, volunteer service or domestic chores may expose the patient to hazards without any relation to work or responsibility on the part of an employer. Many people engage in hobbies at home that carry some risk of serious exposure, such as jewelry-making, stained glass making, model airplane building, ceramics, and furniture refinishing. These are, broadly speaking, occupational but are not work-related in the context of workers' compensation entitlement.
The final step is to rule out deception. On occasion, a patient will be injured at home but will then go to work and claim that the injury occurred on the job. It may be impossible for the clinician to know the truth, but many such cases of fraud can be identified from inconsistencies in the history or by checking with the employer regarding the patient's work assignment. Sometimes a patient with a serious injury will claim that it is work-related out of fear that disability coverage will not be available otherwise. This is, of course, illegal. Benefits available under their employee health insurance or, where applicable, state disability compensation, are available in such cases without the need to falsely submit a claim to the workers' compensation board.
Disability is a diminished ability on the part of the worker to compete on the open labor market in the occupation for which the worker is trained and well suited otherwise, due to the effects of an injury or illness or the likelihood of recurrence of the disorder. Disability depends on the degree of functional impairment, the workers' training and skill, the condition of labor market in his or her occupation, and the availability of alternative gainful employment for someone in the same condition.
Disability is not the responsibility of the physician to judge under workers' compensation, social security, or state disability programs. The role of the clinician is to supply accurate information on two important determinants of disability: impairment and prognosis. Although these determinants are very important in any given case, they do not define disability. This is done by adjudicators and review boards in the responsible agency, using criteria that include the claimant's education and the job market. The clinician cannot possibly have the detailed knowledge of local and regional labor market conditions for a wide range of occupations needed for such judgments. Seeing the process from only one side, and hearing the complaints of many disgruntled applicants, it is easy for the clinician to get a distorted view of the system when the judgment does not match his or her expectations. Often, there is a tendency to write an evaluation that exaggerates (or sometimes minimizes) the impairment in order to benefit the patient. Attempts to manipulate the system by over- or under-estimating impairment only intorduce every more confusion into an already imperfect system, however, and refusal to cooperate at all may hurt the patient and undermine the entire process.
Disability may be temporary or permanent, partial or total. Temporary disability exists when the injured worker is recovering but cannot yet return to work. Disability becomes permanent when no further change is expected and the patient's capacity for work will persist at that level for the remainder of his or her economically productive life. Total disability is not a total incapacity to do any meaningful work; it specifically means an inability to compete in the labor market, as defined by the skills necessary for the job. Loss of manual dexterity from any cause might not be totally disabling to a longshoreman, but would be to a surgeon. Partial disabilities are rated on a percentage basis. For example, in California a back injury precluding heavy lifting carries a standard rating of 30% disability, but this is adjusted by occupation. The same injury in a structural steel worker would be rated 44% disability and for a lawyer 23%, with an additional adjustment in each case by age.
The most practical approach to correct disability evaluation by the clinician is to obtain guidelines from each of the programs most likely to be encountered in practice and to follow the AMA Guide to the Evaluation of Impairment. What the programs require from the clinician is a clear, unambiguous statement in the most quantitative possible terms of what the patient can and cannot do compared to the patient's capabilities before the disorder. When a succession of injuries has taken place, a clear statement is needed describing how each has progressively limited function. This change should be documented or quantified whenever possible by using objective measurements such as range of motion, grip strength, visual acuity, forced expiratory volume in one second, or distribution of sensation.
The clinicial is frequently asked to speculate on what percentage of the patient's disability may have been due to a given exposure or accident or what percentage of the causation is due to a given exposure. This is easiest when the patient's condition can be compared with a previously measured and recorded "baseline". When the patient's own baseline is not known, it is customary to use population-derived averages, such as expected pulmonary function, as an estimate. The interest is to determine what proportion of the loss of function may have been due to the accident or illness, as opposed to other work-related disorders, previous personal illness, or other causes. This is called "apportionment," and can only be an informed judgment in the absence of a baseline evaluation. In general, the apportionment of causation is virtually meaningless. It is simply too uncertain to submit that a given condition was caused by certain exposures in particular proportion, for example that a given case of lung cancer was 50% due to smoking and 50% due to asbestos. Such statements are not accepted by most workers' compensation appeal boards. Apportionment of disability, in the form of the porportion of the degree of impairment observed that has been lost due to the disorder in question is feasible and contributes significantly to a workers' compensation case. Accurate apportionment depends on accurate baseline data, which may be found in preplacement or earlier periodic examinations.
Chronic diseases and health effects which cannot be attributed to just one employer are increasingly recognized and accepted by workers' compensation boards under the legal doctrine of "cumulative injury". This is the concept that a condition arose as the results of countless tiny injuries on the job, allowing the "apportionment" of coverage between carriers on the basis of the duration of exposure a worker sustained in each case. This is particularly important in cases of noise-induced hearing loss and when workers move from job to job in the same industry.
Increasingly, insurance carriers, workers' compensation boards, and disability review boards are demanding objective clinical measurements and are discounting subjective clinical impressions.
American Medical Association. Guide to the Evaluation of Permanent Impairment. AMA, 1971.
Battigelli MC. Determination of fitness to work, in Zenz C. Occupational Medicine: Principles and Practical Applications. Chicago, Year Book Medical Publishers, 1975, pp. 109-116.
Bond MB, Messite J. Preplacement medical evaluation and recommendations, in Zenz C. Developments in Occupational Medicine. Chicago, Year Book Medical Publishers, 1980, pp. 131-138.
California Workers' Compensation Institute. Cumulative Injury in California: The Continuing Dilemma. California Workers' Compensation Institute (San Francisco), 1978.
Chamber of Commerce of the United States. Analysis of Workers' Compensation Laws. Updated annually.
Goldman RH and Peters JM. The occupational and environmental health history. JAMA 1981; 246:2831-6.
Kanner RE. Imapirment and disability evaluation, in Rom WN. Environmental and Occupational Medicine. Boston, Little, Brown, 1983, pp. 43-47.
Key MM, et al.: Occupational Diseases: A Guide to their Recognition. National Institute for Occupational Safety and Health, 1977.
Kusnetz S and Hutchison MK, eds.: A Guide to the Work-Relatedness of Disease. National Institute for Occupational Safety and Health, 1979.
Levy B and Wegman D: Occupational Health. Little Brown, 1983.
Guidotti TL, et al. Taking the occupational history. Ann Int Med. 1983; 99:641-651.
Nylander SW, Carmean G. Medical Standards Project: Final Report. San Bernardino, California, County of San Bernardino, 3rd ed., 1984 (2 volumes).
Schilling RSF, ed. Occupational Health Practice. Boston, Butterworths, 1981.