Instruction 171 in
practice
Dr Elize de Koker
edekoker@webmail.co.za
0794954914
Positive aspects
• 1969- 1994: 3 frequencies used PBI. 3.5% workers
compensable
• 1995- Instruction 168.
4 Frequencies used.
25% lowered to 1.87%.
12.37% workers compensable
• Instruction 171 .
4000Hz added.
Positive aspects
• Pure tone air conduction- gold standard
• Every worker baselined
• Possible to evaluate:
- the influence on the quality of life of workers
- the ability of workers to perform their job
- evaluate the success of HCP
- the cost of compensation to the industry
Future challenges
Although instruction 171 has been an
improvement in our ability to serve the interest
of our workers, Industry and Insurance
Companies there are a few challenges to
recognize
• Pure tone air conduction screening used
• Behavioural test
-environment
-worker
-audiometrist
- equipment
• Differential diagnosis is not possible using only
screening results available
• Tests the whole auditory system
• Incorrect data using only AC test
Challenges
2. Screening results
• Should test cochlear function (where NIHL
develops)
• Oto- acoustic emissions
• High frequency audiometry
• PLH shifts -Current monitoring tool
• Mines report on shift in percentage hearing
loss
• Used for incidence of NIHL, deterioration in
hearing and success of HCP (Milestone)
• PLH actually defines the impairment/disability
and not NIHL
Records kept over 2.5 year period of 5% shifts:
Reasons other than NIHL
- Inter test variance (discussed later)
- Wax
- Middle ear infections
- Perforations
- Pseudohypacusis
(data available for research)
•
•
•
•
Tables place emphasis on 500 and 1000 Hz
Motivation – important for speech reception
NIHL more affected at high frequencies
Conductive losses influence low frequencies
more
• 5% shifts thus often due to outer/middle ear
problems
• Audiology -10 dB inter test differences are
acceptable and not seen as significant.
- between 2 different tests on same day
- 2 test done by 2 different audiometrists
- 2 test done on different equipment
Recognized in BL but not in
- compensation calculations
- monitoring of NIHL
- milestones
Example – inter test differences
Left-dB
Right-dB
20-30
30-40
40-50
40-50
40-50
20-30
30-40
30-40
40-50
50-60
16.4%
32.2%
–
Left-dB
Right-dB
20-30
30-40
40-50
40-50
40-50
20-30
30-40
30-40
40-50
50-60
16.4%
32.2%
% 20.7
• 500 Hz- 20 dB
• 1000 Hz- 30 dB
• 2000 Hz-40 dB
• 3000 Hz-40 dB
• 4000 Hz-50 dB
% 29.8
• 500 Hz-30 dB
• 1000 Hz-35 dB
• 2000 Hz- 45 dB
• 3000 Hz-45 dB
• 4000 Hz-55 dB
• Difference of 9.1%
PLH does not take age into consideration
Normative data needed in RSA.
What is the age distribution of workers being
compensated?
What % shift can be expected with ageing?
• Influence of other diseases
• Possibility of different pathologies in one person
• How do we differentiate between recreational
and occupational exposure
• HIV
- upper respiratory infections
- ARVs
- virus itself
• MDR TB- ototoxicity
• Middle ear pathology
Example of co-morbidity
• Asymmetry
Challenges
6. Unavailability of industry BLs
• Difficult for audiologist to make appropriate
recommendations
• Have to do 2 tests without a BL