Data coding

Results obtained from conducting hearing tests and tympanometry were brought together and coded in different ways (described below) to provide information on the incidence and severity of hearing deterioration, the overall description of hearing loss severity, and the type of hearing loss.

4.2.5.1 Defining and grading hearing deterioration

In Chapter 2 it was discussed that there are different methods for determining hearing deterioration, and that, combining findings from Konrad-Martin et al. (2010) and Simpson, Schwan and Rintelmann (1992), it appeared that ≥15dB shift in threshold, across two or more adjacent frequencies was the most appropriate for determining a clinically significant deterioration in hearing. This definition is used within the CTCAE criteria produced by NCI, with the latest version being version 4.03 (NCI, 2010) prior to starting the project. The

CTCAE criteria for hearing were used in some of the studies discussed in the literature review (Cheraghi et al., 2015; Theunissen et al., 2014b). The CTCAE criteria are familiar to the oncologists at the study centre, as the scale is used for assessing whole body systems and the impact of cancer treatment. Therefore, the CTCAE scale was used in this study to enable results to be readily understood by both oncology and audiology disciplines.

The CTCAE scale (in Appendix 4.2) has a grading system on hearing deterioration that may follow cancer treatment, with Grade 1 being the most minor deterioration, and Grade 4 the most major. A Grade 1 deterioration in hearing for adults enrolled in a hearing-monitoring programme (for a 1, 2, 3, 4, 6 and 8kHz audiogram of air conduction thresholds) is one where there is an average threshold shift of between 15 and 25dB across two contiguous frequencies in at least one ear. For this study, a clinically significant loss was defined as any grade of deterioration, when comparing pre-treatment hearing thresholds with those

obtained at the end of treatment or at 3-month follow-up post treatment. Air conduction threshold values were used, rather than bone conduction, to demonstrate a change in functional hearing, although both air and bone conduction results were recorded. Air conduction thresholds provided the overall level of hearing, regardless of whether the

hearing change was permanent or temporary, whereas bone conduction thresholds provided levels of more permanent loss. For this study, it was important to determine overall hearing and the impact of hearing loss, whether temporary or permanent, on patients. Any graded change in hearing was included in the statistic for determining the incidence of hearing deterioration, as any grade may be detrimental to patients, particularly if participants already possessed hearing loss prior to treatment. In addition, hearing loss had the potential to deteriorate further with time (Bentzen and Trotti, 2006).

Hearing deterioration was graded according to the four numerical grades for hearing in the CTCAE criteria (see Appendix 4.2). The criteria used a comparison of air conduction hearing thresholds measured at 1, 2, 3, 4, 6 and 8kHz obtained pre-treatment with those obtained at either the end of treatment or at 3-month follow-up post treatment. Graded data were

entered and analysed as categorical data in an excel spreadsheet. Using comparison of 3- month follow-up hearing levels with those obtained pre-treatment, participants who had any grade of hearing deterioration were eligible for recruitment for the second phase of the study. A full sampling framework for the qualitative phase is provided in section 4.3.1 of this chapter.

4.2.5.2 Defining descriptors of hearing level and types of hearing loss

There are different ways to describe levels of hearing, mainly based on which country data are derived from. This study used the UK system, summarised in Table 4.1:

Descriptor Average hearing threshold levels (dBHL)

No loss (normal hearing) <20

Mild hearing loss 20-40

Moderate hearing loss 41-70

Severe hearing loss 71-95

Profound hearing loss In excess of 95

Table 4.1 Descriptors of hearing level (British Society of Audiology, 2011)

The BSA describes hearing levels based on the average of air conduction pure tone frequencies at 0.25, 0.5, 1, 2 and 4kHz. Using these criteria, the researcher was able to establish the proportion of participants in the study project within each severity level of hearing loss. However, there are no statistics using these BSA criteria for comparing the proportion of people in the UK who have hearing loss with those who have normal hearing.

In addition to air conduction thresholds, bone conduction thresholds were measured to determine hearing through direct stimulation of the cochlea, and both these thresholds were used to determine types of hearing loss. The type of hearing loss for each ear was

determined to assess potential temporary or permanent hearing change using BSA guidelines for tympanometry (BSA 2013), and PTA as follows:

• Normal hearing: air conduction hearing thresholds between 0.25 and 8kHz ≤ 20dBHL

• Conductive hearing loss: bone conduction thresholds between 0.5-4kHz ≤ 20dBHL, and air-bone gap in at least one of the frequencies between 0.5-2kHz ≥ 15dB. • Sensorineural hearing loss: air conduction hearing thresholds between 0.25 and

8kHz > 20dBHL, and air-bone gap between 0.5-2kHz < 15dB.

• Mixed loss: bone conduction thresholds between 0.5-4kHz > 20dBHL, and air-bone gap in at least one of the frequencies between 0.5-2kHz ≥ 15dB.

Tympanometry was performed to confirm normal hearing or to assist with the classification of hearing loss type as being conductive, mixed, or sensorineural. Therefore, for this study, the BSA guidelines on PTA and tympanometry were used to describe hearing level, and classify type of hearing loss before treatment, at the end of treatment and at 3-month follow- up.