Study instruments

This section describes the questionnaire tool that was translated from English to Tonga, piloted and refined in Binga, Zimbabwe before it was used by this study. The referral pure-tone screening instrument used was a Kamplex audiometer, which is also briefly described in this section.

3.7.1 “Questionnaire” screen

The questionnaire designed by Dube’s (1995) study was revised and used in collecting data for this study.

The questionnaire is divided into two Parts:

a) “Part 1”; General information for each child, collects the bio-data such as: name o f child, date of birth, address, birth weight, mother or carer’s worries concerning child not able to hear and history o f deafness in the family.

b) “Part 2” Age specific (10-questions plus observations scale); 1. Section‘A ’ 36-48 months

2. Section ‘B ’ 49-60 months 3. Section ‘C’ 61-72 months

Each section has 10-questions asking the mother or carer about her observations regarding her child’s hearing, e.g.:

• Can s/he point to at least one part of her/his body, when you ask her/him in a quiet voice?

• Does s/he watch the speaker’s face and mouth?

In addition to the 18 questions for each age group the interviewer records observations for the full version of the questionnaire (see the “Questionnaire” screen Appendix I and II).

Observations (OB) Scale: the interviewer is requested to place a cross (X) on the scale provided, indicating her or his observations about the child’s hearing responses to the interviewer and mother or carer’s instructions. The scale used is presented in Fig. 3.2.

Fig. 3.2: Observations scale to plot the child’s hearing responses

Never Always

10

A tick in a Yes or No box as shown in Box 3.3 below indicated the interviewer had determined if a child had passed or failed the screen.

Box 3.3: Evaluation of hearing loss: the interviewer’s summary.

Indication of hearing loss:

Yes [ ]

N o[ 1

The questionnaire results are summarised by the statement in Box 3.3 to which the response is either yes or no. The evaluation does not diagnose hearing impairment but can only suspect hearing loss in the child screened. The children who were interviewed by use of this questionnaire were also subjected to pure-tone screening sessions where a screening audiometer was used.

A Kamplex screening audiometer is briefly described below.

3.7.2 Kamplex screening audiometer

The Kamplex screening audiometer (calibrated, which expires early 2002) was used for pure-tone screening hearing loss in children aged 36-72 months. Pure-tone audiometry could be a diagnostic or screening protocol. It uses calibrated equipment that produces pure-tones.

This study used air conduction by using earphones positioned on both ears. Four frequencies, 0.5 k, Ik, 2k and 4k, were used. Initially, an attempt was made to

measure the threshold level at which an individual child listened through standard earphones to hear different frequencies. That was impossible because children, especially the 3-year-olds, displayed a short listening span. Compounded by the ambient noise, it was practically impossible to evaluate hearing threshold above 40dBHL even though it is still a significant important measure. The protocol was then revised and set at SOdBHL.

This pure-tone screening protocol was used as a gold standard to compare the results o f the questionnaire against pure-tones.

3.7.3 Suitability of the study instruments

Reliability is critical for evaluating the suitability of a test to accurately measure the characteristic or ability o f interest. Reliability is an important concern for the user of any test because it gives an indication of the accuracy o f the test. Higher levels of reliability indicate less error variance and consequently high correspondence between the observed score and the individual’s true score (true positives and true negatives in the case of a hearing screen as opposed to false positives and false negatives).

Internal consistency reliability assesses the degree to which items on the test are constant in the measurement of the underlying construct. Operationally, this reliability is examined by the intercorrelations among the item test (Kirkwood, 1994).

Interviewing mothers and carers of children aged 36-72 months was an appropriate procedure adopted by this study. In theory the 3 year-olds are developmentally ready for the pure-tone testing that is used as the gold standard. Secondly, there are pre­ schools established in the rural areas in Binga for 3-6 year-olds.

The advantages of the interview method are:

i. It is interactive and an adaptable way o f finding out about a child’s hearing. ii. The face-to-face relationship offers the possibility of clarifying some unclear

Tonga dialects, following up interesting responses and investigating underlying motives in a way that postal and other self-administered questionnaires could not.

iii. Non-verbal cues give messages, which help in understanding the verbal responses, which could possibly change or even, in extreme cases, reverse their meaning.

iv. It can be used by non-specialists and is cheap.

However, this method has few disadvantages:

i. Profitable use o f this interactive approach calls for considerable skill and experience in the interviewer. This was made more likely by training and supervising the data collectors (fieldworkers).

ii. The standardisation of the questionnaire implies that it inevitably reduces concerns about inter-and intra-user variability. But biases are difficult to rule out.

iii. Interviewing is time-consuming. The interview sessions obviously varied in length o f time. Anything under half an hour is unlikely to be valuable; anything going much over an hour makes unreasonable demands on busy interviewees, and could have the effect of reducing the number of persons willing to participate, which may in turn lead to bias in the sample achieved.

The questionnaire used in this study demands a highly structured interview, with a predetermined set of questions. The responses are recorded on a standardised schedule. This is a deliberate design because it is expected that the questionnaire might be a screening protocol. It would need to be tested and standardised later if found reliable in detecting permanent hearing loss in children.