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Occupational Medicine Advance Access published online on January 21, 2008
Occupational Medicine, doi:10.1093/occmed/kqm146
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© 2008 The Author(s). This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Diagnosing and reporting of occupational diseases: a quality improvement study

D. Spreeuwers1, A. G. E. M. de Boer1, J. H. A. M. Verbeek1,2, M. M. van Beurden1 and F. J. H. van Dijk1

1 Coronel Institute of Occupational Health, Academic Medical Centre, University of Amsterdam, the Netherlands
2 Finnish Institute of Occupational Health, Knowledge Transfer Team, Kuopio, Finland

Correspondence to: D. Spreeuwers, Coronel Institute of Occupational Health, Academic Medical Centre, University of Amsterdam, PO Box 22700, 1100 DE Amsterdam, the Netherlands. Tel: +31 20 5665387; fax: +31 20 5669288; e-mail: d.spreeuwers{at}amc.uva.nl


   Abstract
Top
 Abstract
Introduction
 Methods
 Results
 Discussion
 Key points
 Conflicts of interest
 References
 
Aim To assess the need for quality improvement of diagnosing and reporting of noise-induced occupational hearing loss and occupational adjustment disorder.

Methods Performance indicators and criteria for the quality of diagnosing and reporting were developed. Self-assessment questionnaires were sent to all occupational physicians recorded on the Netherlands Centre for Occupational Diseases database. The performance of responding occupational physicians was then assessed by separate scores per performance indicator and by a total quality score.

Results Twenty-three questionnaires on noise-induced occupational hearing loss and 125 questionnaires on occupational adjustment disorder were available for analysis. The mean quality score for diagnosing and reporting was 6.0 (SD: 1.4) for noise-induced occupational hearing loss and 7.9 (SD: 1.5) for occupational adjustment disorder on a scale of 0–10. For noise-induced occupational hearing loss, there was a need for quality improvement of the aspects of medical history, audiometric measurement, clinical diagnosis of the disease and reporting. For occupational adjustment disorder, the assessment of other non-occupational causes needed improvement.

Conclusions The quality of diagnosing and reporting could be improved for noise-induced occupational hearing loss and occupational adjustment disorders. Information, education and practical tools are proposed for quality improvements.

Keywords      Occupational diseases; quality assessment; registration


   Introduction
Top
 Abstract
 Introduction
Methods
 Results
 Discussion
 Key points
 Conflicts of interest
 References
 
In many countries, the registration and reporting of occupational diseases is an important source of information for preventive policy. National registration systems in most countries derive their figures from compensation schemes for occupational diseases, while in a few countries there are voluntary registration schemes in addition to national registries [1–3]. Several authors have criticized the reliability of the figures provided by national registries and the comparability between countries because of the differences in registration systems. Moreover, the lack of coverage of the working population, the high degree of underreporting and poor quality control add to the limited reliability of the figures [4–6].

Another important determinant affecting the quality of the registration of occupational diseases is the availability of diagnostic criteria or case definitions. Most compensation systems have strict criteria for the acknowledgement of occupational diseases, whereas other reporting schemes often apply criteria less strictly and also offer the possibility to report suspected cases. Criteria should preferably be based on evidence from aetiological and diagnostic research, for example, like those developed for work-related upper-extremity musculoskeletal disorders and for work-related low back pain [7,8]. Physicians should use these criteria or case definitions in diagnosing and reporting. However, poor performance by physicians in diagnosing and reporting occupational diseases has been reported [4,9–11].

During this study, all companies in the Netherlands with at least one employee were legally obliged to have a contract with an occupational health service, which means that nearly all employees had access to an occupational physician. The total number of employees in the Netherlands was 6.116 million in the study period. The largest sectors were health care and welfare (967 000 employees), industry (966 000 employees), repair and trade (907 000 employees) and business services (715 000 employees) [12]. The number of occupational physicians in the Netherlands was 1774 in the study period [13]. Occupational physicians are obliged by law to report occupational diseases since 1999. The Dutch government has made the Netherlands Centre for Occupational Diseases (NCOD), the institute responsible for the registry of occupational diseases. In the Netherlands, a compensation scheme for occupational diseases does not exist and thus occupational diseases are only notified for preventive purposes.

As good-quality diagnoses are a prerequisite for reliable figures on occupational diseases, the NCOD has developed guidelines on the diagnosis of occupational diseases. These guidelines are available through the Internet and are used as training material for occupational physicians during their vocational training [14]. The guidelines include criteria for the clinical diagnosis of the occupational disease and for the minimum level and duration of exposure to risk factors at work. However, when occupational physicians report cases, they are not required to indicate if the criteria from the guidelines have been met. Therefore, we decided to study the quality of diagnosis and reporting and to assess the needs for quality improvement.

Our study was restricted to two important occupational diseases: noise-induced occupational hearing loss and occupational adjustment disorder. Adjustment disorders (DSM-IV definition) are maladaptive reactions to identifiable psychosocial stressors occurring within a short time after onset of the stressor. They are manifested by either impairment in social or occupational functioning or by symptoms (nervous exhaustion, nervous breakdown, depressive thoughts, etc.) that are in excess of a normal and expected reaction to the stressor. The presence of depressive disorders and anxiety disorders has to be excluded. We have chosen these diseases because they are relatively prevalent and represent two different types of guidelines. The guideline for noise-induced occupational hearing loss is derived from the European list of occupational diseases and is strictly defined with clear quantitative criteria, whereas the guideline for occupational adjustment disorder is less strictly defined and includes mainly qualitative criteria [15]. The disease occupational adjustment disorder is not recorded in the European list as an occupational disease. However, in several registration projects (for example in the Surveillance of Occupational Stress and Mental Illness scheme in the UK), occupational mental ill-health is recorded for preventive purposes [16].

The general objective of this study was to assess the need for quality improvement of diagnosing and reporting of noise-induced occupational hearing loss and occupational adjustment disorder as notified to the NCOD. The specific aims of this study were as follows: (i) To develop performance indicators and criteria for the quality of diagnosing and reporting of cases of noise-induced occupational hearing loss and occupational adjustment disorder. (ii) To assess this quality in cases notified by occupational physicians to the NCOD in terms of compliance to the notification guidelines. (iii) To make a preliminary evaluation of the need for quality improvement.


   Methods
Top
 Abstract
 Introduction
 Methods
Results
 Discussion
 Key points
 Conflicts of interest
 References
 
We developed performance indicators for diagnosis and reporting of occupational diseases to NCOD, based on the Dutch notification guidelines for noise-induced hearing loss and occupational adjustment disorder [17] and the assessment procedure undertaken by occupational physicians. This assessment procedure consists of five steps:

(i) diagnosis of the disease,
(ii) assessment of potential work relatedness as far as evidence exists in the literature,
(iii) exposure assessment in the case studied,
(iv) assessment of other possible non-occupational causes and
(v) conclusion of work relatedness.

If work relatedness is concluded, the disease must be reported to the NCOD. Based on this procedure and on evidence from the literature, the NCOD has developed guidelines for noise-induced occupational hearing loss and for occupational adjustment disorder [14].

For the different steps of the assessment procedure, we formulated one or more performance indicators. We derived two performance indicators from the first step of the generic assessment: medical history (which we considered as an essential step in diagnosing) and clinical diagnosis of the diseases. We summarized the second and third step of the generic assessment in the performance indicator assessment of exposure. The fourth step provided the performance indicator assessment of other possible non-occupational causes. The fifth step corresponds with the performance indicator conclusion about work relatedness. We considered audiometric measurement as an essential element in the diagnosis of noise-induced occupational hearing loss and added it as an extra performance indicator. Finally, we added reporting (which is obligatory in the Netherlands for all occupational physicians) according to the internal criteria of the NCOD as an extra performance indicator for both diseases. Face validity of performance indicators and criteria was tested by asking three senior scientists in the field of occupational health to compare the preliminary performance indicators and criteria with the guidelines and to give a comment. Appendix 1 presents the set of performance indicators and criteria for both diseases.

The quality improvement study was carried out from 1 April 2004 to 1 July 2005. We developed a questionnaire based on the performance indicators and criteria for both diseases, and then asked two experienced occupational physicians to test the feasibility of the questionnaires. Appendix 2 presents the corresponding questionnaires. Next, we sent five copies of a questionnaire on noise-induced occupational hearing loss and five copies of a questionnaire on occupational adjustment disorder to all 1705 occupational physicians recorded in the database of the NCOD and asked them to participate in the study. This database contains the details of occupational physicians who have notified one or more occupational diseases to the NCOD since the database was started in 1997. We asked the physicians to fill in a questionnaire as soon as they reported to the NCOD a case of either noise-induced occupational hearing loss or occupational adjustment disorder.

The Dutch reporting form for occupational diseases comprises the following items: name and code of the occupational health service, name and code of the physician, date of notification, patient file number, year of birth and sex of the patient, occupation, economic sector, ICD-10 code and description of diagnosis, causes, pre-existent conditions, degree of certainty of diagnosis (probable or sure) and context of detecting and advice given. The questionnaire comprised the following items corresponding to the reporting form for occupational diseases: name and code of the physician, date of notification, year of birth and sex of the patient and ICD-10 code of the diagnosis. Data from each questionnaire were linked to the reported cases' database with the occupational physician code and patient data. For each reported case, we scored the performance indicators on the basis of the corresponding questionnaire. A performance indicator was scored 1 if the criteria were satisfied and 0 if the criteria were not satisfied.

For each performance indicator, the percentage of cases in which the criteria were met was calculated for both diseases. If the criteria for the performance indicator were fulfilled in every submitted case, the score for that performance indicator would amount to 100%. We considered a score of <60% for a performance indicator as a need for quality improvement. Next, we calculated a score per case by summing up all performance indicators that were met for both diseases. In the calculation, all performance indicators had the same weight. Then, we calculated the mean score for all cases of a disease. To present the scores on a scale of 0–10, we divided it by the number of performance indicators, i.e. 7 for noise-induced occupational hearing loss and 6 for occupational adjustment disorder and subsequently multiplied it by 10. We called this the total quality score.

Furthermore, we calculated the intra-doctor variability of the performance of diagnosing and reporting for both diseases. We determined this variability by calculating a coefficient of variation [CV = (SD/M) x 100] of the total quality score for all occupational physicians who reported more than one case of either noise-induced occupational hearing loss or occupational adjustment disorder. Next, we calculated the mean coefficient of variation as a measure for the mean intra-doctor variability. A value of <20% is considered as low variability, of 20–40% as moderate variability and of >40% as high variability [18]. The inter-doctor variability was not calculated because the participating physicians assessed different cases.


   Results
Top
 Abstract
 Introduction
 Methods
 Results
Discussion
 Key points
 Conflicts of interest
 References
 
Ten occupational physicians completed a total of 23 questionnaires on noise-induced occupational hearing loss, while 52 completed 125 questionnaires on occupational adjustment disorder. Three physicians returned questionnaires both on noise-induced occupational hearing loss and occupational adjustment disorder. The respondents came from 25 different occupational health services. One of the respondents was self-employed. The respondents reported more cases of all occupational diseases than the average. The mean number of cases of all occupational diseases reported by the respondents was 10.7, while the mean number of cases of all occupational diseases reported by all occupational physicians was 6.2.

In the study period, a total number of 1440 cases of noise-induced occupational hearing loss were reported by 395 occupational physicians to the National Registry. In 87 cases, the reporting physician could not be identified. A total number of 842 cases of occupational adjustment disorder were reported by 145 occupational physicians to the National Registry. In 685 cases, the reporting physician could not be identified, mostly because they were reported in batches by the organization of the reporting occupational physicians.

The mean age of the cases reported for noise-induced occupational hearing loss was 48 years (range: 32–58 years). All these cases were males. The mean age of the cases reported for occupational adjustment disorder was 44 years (range: 19–61 years). Of these cases, 57 were men (46%) and 68 were women (54%). For the total number of cases reported to the National Registry in the study period, the mean age of the reported cases was 49 years (range: 20–69 years) for noise-induced occupational hearing loss and 44 years (range: 20–65 years) for occupational adjustment disorder. The percentage of males was 98% for noise-induced occupational hearing loss and 54% for occupational adjustment disorder.

Table 1 presents the scores of the performance indicators for the quality of diagnosing and reporting and the total quality scores. The mean quality score on a scale of 0–10 was 6.0 (SD: 1.4) for noise-induced occupational hearing loss and 7.9 (SD: 1.5) for occupational adjustment disorder. In 23 cases (18%) of occupational adjustment disorder, the maximum score was achieved by the physicians, while for noise-induced occupational hearing loss the maximum quality score was not achieved in any of the cases.


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  		Table 1. Percentage and absolute number of cases in which the criteria for the indicators were met and total quality score (0–10) for performances on diagnosing and reporting

 
For noise-induced occupational hearing loss, the criteria were met in <60% of the cases for the performance indicators: medical history, audiometric measurement, clinical diagnosis and reporting. For occupational adjustment disorder, this was the case only for the performance indicator regarding other non-occupational causes.

The intra-doctor variability was measured for all occupational physicians who returned more than one questionnaire. Six occupational physicians (60%) returned more than one questionnaire of noise-induced occupational hearing loss. Four physicians returned two questionnaires, one returned three questionnaires and one returned eight questionnaires. Thirty occupational physicians (58%) returned more than one questionnaire of occupational adjustment disorder. Fifteen physicians returned two questionnaires, three returned three questionnaires, six returned four questionnaires, two returned five questionnaires, three returned six questionnaires and one returned twelve questionnaires. The mean intra-doctor variability for noise-induced occupational hearing loss was 28% (range: 0–61%) and 14% (range: 0–47%) for occupational adjustment disorder.


   Discussion
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
Key points
 Conflicts of interest
 References
 
The quality assessment of the performance of diagnosing and reporting by Dutch occupational physicians resulted in a mean total quality score of 6.0 for noise-induced occupational hearing loss and 7.9 for occupational adjustment disorder on a scale of 0–10. Quality improvement in diagnosing and reporting could be attained by improving performance on taking of medical history, audiometric measurement, clinical diagnosis and reporting for noise-induced occupational hearing loss and on the performance of assessment of other possible non-occupational causes for occupational adjustment disorder. The intra-doctor variability of the performance was low for occupational adjustment disorders and moderate for noise-induced occupational hearing loss.

The strengths of our study include the availability of Dutch guidelines for the two occupational diseases. We used the guidelines to frame our performance indicators and criteria, as they provide clear criteria for the medical history, assessment of the clinical diagnosis, exposure and other possible non-occupational causes and the conclusion of work relatedness. Every Dutch occupational physician receives information about the guidelines for reporting occupational diseases in the basic specialist training or in postgraduate training. The guidelines are available from the NCOD website, and occupational physicians can consult a helpdesk for support in diagnosing and reporting occupational diseases.

Another strength of our study includes the provision of specific indications of ways to improve the quality of diagnosing and reporting, whereas most studies present only the observation that the recognition and reporting of occupational diseases by physicians is inadequate and that better training is needed, without assessing the issues on which quality improvement should occur [4,9–11].

A limitation of this study is the likely existence of a selection bias. It is possible that the physicians who returned the questionnaire have a more positive attitude towards reporting and possess more knowledge of occupational diseases. This might have led to an overly favourable picture of the quality of diagnosing and reporting of occupational diseases. The measurement of performance based on self-reporting might also have contributed to a more favourable outcome. Nevertheless, the study does provide important clues for quality improvement.

Another limitation lies in the interpretation of the quality score. The results of this study show better quality scores for occupational adjustment disorder than for noise-induced occupational hearing loss. This could be due to the different contents of the guidelines. The guideline for noise-induced occupational hearing loss is far more detailed and explicit than the guideline for occupational adjustment disorder. It is therefore more difficult to meet the requirements of the guideline for noise-induced occupational hearing loss.

A prerequisite for good-quality diagnosing and reporting of occupational diseases is evidence-based guidelines [19,20]. This calls for evidence-based case definitions of occupational diseases [20–22]. Criteria for occupational diseases must be based on epidemiological studies and research focused on revealing aetiological mechanisms. In reality, there is considerable variability between countries in guidelines or criteria for occupational diseases. Many countries maintain a national list of occupational diseases for compensation purposes. The European Union has a list with corresponding information notices on the listed occupational diseases [15]. Member States are requested to implement the diseases of the European Union list in their own legislation. Accordingly, many national lists are derived from the European Union list, but are adapted to the specific legislation of the relevant country. The evidence base of the present and future national lists might be questioned and evaluated. If we want to be able to compare valid figures on occupational diseases between countries, the evidence base of the definitions and criteria must be evaluated and enhanced, and the definitions and criteria used in the different countries must be harmonized. These are prerequisites for starting a quality improvement process on a national or international level.

The low intra-doctor variability for occupational adjustment disorder and the moderate variability for noise-induced occupational hearing loss suggest that quality improvement will be achieved not so much by focusing on a group of low performers, but mainly by focusing on the improvement of performance on specific aspects of the diagnosing and reporting procedure. Our study identifies the areas in which quality improvements of diagnosis and notification could be achieved. For noise-induced occupational hearing loss, these are medical history, audiometric measurement, clinical diagnosis of the disease and reporting, while for occupational adjustment disorders the area for improvement is the assessment of other possible non-occupational causes.

A proper knowledge of the guidelines is a prerequisite for good-quality diagnosis and reporting. However, many occupational physicians do not have time to check the guidelines in their daily practice. This indicates the need to facilitate diagnosing and reporting by practical tools; for example, user-friendly decision-making software that is preferably linked to the electronic patient file.

The findings of this study could be helpful in exploring the need for quality improvements in the reporting and registration of occupational diseases. Improvement in the quality of diagnosing and reporting will increase the reliability of the figures produced. Besides better education and information, Internet tools for electronic exchange of information on occupational diseases should be considered [23].


   Key points
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Key points
Conflicts of interest
 References
 

  • Quality of diagnosing and reporting of noise-induced occupational hearing loss can be improved.
  • For noise-induced occupational hearing loss, quality improvement can be achieved on the aspects: medical history, audiometric measurement, clinical diagnosis of the disease and reporting.
  • For occupational adjustment disorders, quality improvement can be achieved on the aspect assessment of other possible non-occupational causes.


   Conflicts of interest
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Key points
 Conflicts of interest
References
 
None declared.


Appendix 1. Performance indicators and criteria for the quality of diagnosing and reporting of noise-induced occupational hearing loss and occupational adjustment disorder, based on the Dutch guidelines

Performance indicators Criteria
Noise-induced occupational hearing loss
    Medical history Always ask for complaints of tinnitus or hearing loss.
Always ask for congenital or early acquired hearing loss, otosclerosis, vertigo, operations and/or injuries of the ear in the case history.
    Audiogram Always perform an audiogram under standard conditions (temporary threshold shift must be excluded, i.e. no noise exposure in the preceding 6 h).
    Diagnosis The diagnosis of noise-induced hearing loss has to be correct:
    the hearing threshold at 4 kHz exceeds the HL-10 for the same sex and the same age group (following ISO 7029),
    the difference between the hearing thresholds of the left and the right ear at 4 kHz is ≤15 dB,
    there are no signs of congenital or early acquired hearing loss, otosclerosis, vertigo, operations and/or injuries of the ear in the medical history and
    the hearing loss at 1 kHz does not exceed the HL-10 for same sex and the same age group.
If one ear meets the first criterion but not all criteria, expert judgement is required.
    Exposure Always ask for the occupations of the patient in chronological order and if noise exposure of >80 dB has occurred and, if so, the duration of the exposure. Always verify if noise measurements have been carried out on the workplace and ask for the results.
    Other non-occupational causes Always ask for possible noise exposure of >80 dB outside the working environment.
    Conclusion The conclusion of occupational hearing loss has to be correct:
    the diagnosis with ICD-10 code H 83.3 has to be set and
    there has been an occupational exposure exceeding 80 dB(A) for >6 months, likely on the basis of the medical history or confirmed by workplace measurements.
    Reporting The notification meets the internal criteria of the Netherlands Centre for Occupational Diseases.
Occupational adjustment disorder
    Medical history Always ask for key symptoms of anxiety disorder (excessive fear) or depression (depressed mood and loss of interest in all areas of life throughout the day for >2 weeks).
Always ask for psychological or somatic complaints.
Always ask for the onset of complaints and their duration.
Always ask for traumatic experiences or the death of a beloved person in the preceding 2 months.
Always ask for substantial restraints in social or occupational functioning (sickness absence or dysfunctioning).
    Diagnosis The diagnosis of adjustment disorder has to be correct:
    there are one or more psychological or somatic complaints,
    there are substantial restraints in social or occupational functioning and
    depression, anxiety disorder, post traumatic stress disorder or mourning has been excluded.
    Exposure Always ask for stressors in the dimensions: pressure of work, possibilities for self-organization of work, social relations.
Always ask for onset of stressor and duration.
Always ask if other employees have the same complaints.
Always ask for the judgement of the patient concerning the work relatedness of the complaints.
    Other competing causes Always ask for non-occupational life events and stressors.
    Conclusion The conclusion of occupational adjustment disorder has to be correct:
    the diagnosis with ICD code F 43.2 has to be set,
    there are one or more stressors in the working environment and
    the relative contribution of occupational stressors is greater than the relative contribution of non-occupational stressors.
    Reporting The notification meets the internal criteria of the Netherlands Centre for Occupational Diseases.


Appendix 2. Questionnaires for the assessment of diagnosing and reporting performance

General questions Occupational physician (code):
ICD code diagnosis reported case:
Year of birth reported case:
Sex reported case:
Date of notification:
Noise-induced occupational hearing loss
  1. What are the most important complaints (maximum 5) in the medical history concerning the diagnosis of occupational hearing loss? Only mention the complaints you actually asked for.
  2. On the basis of the absence of which complaints or personal risk factors (maximum 5) do you exclude other hearing disorders? Only mention the complaints you actually asked for or the complaints that were already registered in the patient's file.
  3. What is the date of the last audiogram?
    When the audiogram was performed, how many hours had elapsed since the patient had stopped working?

  4. Data from the last audiogram: HL-10 by 4 and 1 KHz for both left ear and right ear.
  5. Occupations in chronological order with damaging exposure to noise and duration of exposition.
  6. Are noise measurements available? If so, what is/was the noise level [in dB(A)] for how many hours per day?
  7. Has the patient been exposed to non-occupational damaging noise? If so, which exposures?
Occupational adjustment disorder
  1. What are the most important complaints (maximum 5) in the medical history concerning the diagnosis of occupational adjustment disorder? Only mention the complaints you actually asked for.
  2. How long have these complaints existed (in weeks)?
  3. On the basis of the absence of which complaints (maximum 5) do you exclude other psychiatric disorders? Only mention the complaints you actually asked for.
  4. Did traumatic events or the death of a beloved person occur in recent months? If so, which event/person?
  5. What is your opinion about the social and occupational functioning of the patient: not limited or substantially limited?
  6. What were the most important stressors in the work environment before the onset of the disorder and when was the onset of the stressors?
  7. Were the following stressors present in the work environment? High work pressure, too much or too little work, emotionally demanding work, too much or too little autonomy, task uncertainty, do not like the work, demanding physical factors, conflicts or mobbing, lack of appreciation, lack of support, lack of information, insufficient reward, future uncertainty, merger or reorganization.
  8. Do other employees have work-related complaints?
  9. What is the opinion of the employee him- or herself about the work relatedness of the complaints?
  10. Has the patient been exposed to non-occupational stressors or life events? If so, what exposures, what stressors or life events, when was the onset and what was the duration?


   References
Top
 Abstract
 Introduction
 Methods
 Results
 Discussion
 Key points
 Conflicts of interest
 References
 

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