What do the hearing test results categories mean?

Righty, how to explain this in a way that makes sense without writing out an instruction manual for doing an audiometric test. Or making you run a very real risk of death by boredom...

Source of the reference standards for workplace audiometry

All workplace audiometric tests are assigned one of four categories, with the definition of these categories and how to calculate them being given in L108 which is the source of the standards.

Most audiometers do this automatically and calculating results is not something employers or someone purchasing a series of hearing tests from a prover needs to know how to do, you just need to know what the categories are.

Standards are relative - they change

One important principle is that categories of audiometry result are relative and move, they are not fixed. What I mean by this is that when assessing someone's result the comparison is made against the expected standard of hearing for their age, not against a fixed point. This is because hearing naturally deteriorates with age so there is no point comparing a bloke in his mid 40s to the ideal hearing standard of a woman in her early 20s. So, when calculating a category of result, the person's age and gender are both taken into account, and if there is a history of previous hearing tests available as well then that is also used for comparison.

This means that someone in their mid-40s could have a worse level of hearing than someone in their early 20s but have a better result classification because for their age, their hearing is good, whereas the 20 year old may have good hearing overall but for their age it should be better.

Categories of hearing test result for workplace audiometry

There are four fixed categories of result and all workplace hearing tests will be assigned one of these.  

Category 1

This is the 'everything is normal' result. It means that for the attendee's age, their hearing is normal. That doesn't automatically mean the hearing is excellent as if they are older then normal age-related losses will almost inevitably be present, but for their age it is where it should be. All is good and nothing further is required until their next test is due in no more than three years.

Category 2

The best way to phrase this is 'normal, ish, but getting a bit low and towards the lower end of the normal range'. Category 2 means their hearing is still within the normal range for their age and gender but is skirting close to the lower limits of what is acceptable. It's a heads-up that care is needed. As with Category 1, no follow-up action is needed other than the ongoing retest programme, with the next test being due in about two years.

Category 3

This one means their hearing is below the expected standards for their age and gender - it is poorer than it should be. If there is no medical history supporting this loss, such as it being previously diagnosed or some other medical condition which impacts on hearing, then the recommendation is that this one is referred to a medical professional for further examination to try and determine the cause of the losses and if any treatments are available. It is important that Category 3 people wear hearing protection in high noise areas to stop any ongoing deterioration. 

Just to repeat the ‘it is all relative’ principle above, Category 3 doesn't necessarily mean their hearing is definitively poor and that they are deaf, it means it is not as good as it should be for their age and gender. This means Category 3 people do not have to be removed from high noise areas just because they are Category 3.

Category 3 people are normally retested every year.

Category 4

This one is slightly different to the other three. The first three are all calculated by comparing the result against a reference standard for their age, but Category 4 is a calculation comparing the current result against a previous result for the attendee. It is a measure of rate of change rather than a measure against a fixed standard. 

This does complicate things a little as someone could be Category 4 because their hearing has deteriorated when compared against a previous hearing test, but their hearing could still actually be very good. It was just even better last time. It is important to remember therefore that Category 4 is an indication of change, not of level of hearing. As with Category 3, the standard is for referral unless there is something previously known which is causing the reduction and the retest period is one year.

How the HSE explain it

For reference and comparison, this is how the HSE explain the categorisation of results in Appendix 5 of L108, page 118:

 HSE categorisation scheme for workplace audiometric tests

HSE categorisation scheme for workplace audiometric tests

Category saying ‘unilateral’

There is a sub-classification called ‘unilateral’. This means one ear is worse than the other, so you may see ‘Category 3u’ which means one ear was a Category 3, and the other ear was better (otherwise it would just say Category 3 if they were both rubbish).

If one ear is worse than the other, whichever is the lowest result will be the overall classification given for that hearing test.

Confusion caused by comparing results of different ages

It's worth clarifying that all these categories of result are dependent on a person's age and gender. For all the lengths we go to to make sure the results are kept confidential, you can bet the mortgage that the first thing attendees will do is go back to their workplace and compare who got which category of result.

Confusion can arise when someone with a Category 1 result has worse hearing than someone with a Category 2 or Category 3, then they get very head-scratchy and think something's gone wrong, but it hasn't.

Someone in say their 50s has a lot of leeway in the calculation for their result of where their hearing should be, taking natural losses over time and age into account. As the Category is based on how well they are performing for their age, the 50-odd year old could have good hearing for their age and be Category 1, but still have some quite big losses compared to a teenager. Someone in their 20s however could have small losses and be less good for their age than they should be, so come in as a Category 2 or even 3, but side by side their hearing could still be better than the person in their 50s. It is the impact of age which makes the difference.