Is it reasonable to use 1 and 8 kHz anchor points in the medico‐legal diagnosis and estimation of noise‐induced hearing loss?

Abstract

'Carte Blanche' use of 1 and 8 kHz anchor points is probably unreasonable and may well be unsafe in the medico-legal diagnosis and estimation of noise-induced hearing loss.

Current insights in noise-induced hearing loss: A literature review of the underlying mechanism, pathophysiology, asymmetry, and management options

“…High frequencies are also typically affected by presbycusis; therefore the notch may disappear with aging, making it difficult to differentiate NIHL from presbycusis. Whether or not chronic noise exposure can also result in hearing loss at 8 kHz is debated [57]. With further noise exposure, the notch can get deeper and wider eventually involving lower frequencies such as 2 kHz, 1 kHz and 0.5 kHz [58, 59].…”

Further observations on the anchor point methodology: is it reasonable to use 1 and 8 kHz anchor points in the medico‐legal diagnosis and estimation of noise‐induced hearing loss

“…Ali et al . (2015) highlighted the fundamental flaws in the carte blanche use of 1 and 8 kHz anchor points in the medico‐legal context of noise‐induced hearing loss (NIHL). Blindly trusting this method to deliver justice without seeking the answers to the genuine and fundamental questions about its validity would prevent the analysis of the very basics.…”

“…Blindly trusting this method to deliver justice without seeking the answers to the genuine and fundamental questions about its validity would prevent the analysis of the very basics. Nevertheless, the anchor point concept does have a limited place, in carefully selected cases and only in association with official age‐related hearing loss (ARHL) standards.…”

“… The guideline paper borrowed the anchor point concept and used it for diagnostic purpose; however, Ali et al mentioned the estimation of NIHL in relation to a court case where 8 kHz anchor point was borrowed for quantification purpose. According to anchor point methodology, the probable diagnosis of NIHL depends upon the required depth of the bulge, which is the difference between statistical ARHL and the measured hearing thresholds . Therefore, in an individual, the value of statistical ARHL used is very relevant to the potential depth of the bulge.…”

“…Therefore, in an individual, the value of statistical ARHL used is very relevant to the potential depth of the bulge. Application of compression factor to ARHL does tend to reduce its value, potentially increasing the depth of the bulge. This may tip the balance from merely a ‘possibility’ to ‘probability’ of NIHL, producing true positive rather than false negative result. The collateral noise damage to 8 kHz could be significant, especially if the noise‐induced notch is at 6 kHz.…”