The value of routine in-the-ear measurement of hearing aid gain.

When selecting the frequency response of a hearing aid, a target is usually selected using a predictive formula from the international literature. Nowadays real ear measurements can readily be carried out to ensure that the real ear gain closely matches the prescribed target. Such measurements are usually only carried out on a subset of patients fitted in the UK, though it has been suggested that they should be carried out on all hearing aid prescriptions. Real ear insertion gains were measured on 319 first-time National Health Service (NHS) hearing aid issues. A total of 181 (57%) failed to come within 10 dB of the target gain at one or more frequencies between 0.25 and 3 kHz. Though there were audiometric differences between those who achieved satisfactory gain and those who did not, there was too much overlap between groups to make any audiometric index or combination of indices of value in predicting the likelihood of failure to achieve target gain. Sixty-eight patients with inadequate real ear gain were invited to attend for alterations to their hearing aid prescription. Twelve (18%) were fitted with a high frequency aid, while the rest were managed by alterations to their NHS aid or to the earmould and tubing. After appropriate changes, 58 (85%) achieved a satisfactory gain. The routine use of real ear insertion gains in all hearing aid fittings would result in many patients having a more accurately fitted hearing aid. As the majority of prescriptions could be adequately improved using NHS hearing aids, the effects on the hearing aid budget would be relatively small.