Reliability and Validity

2.6.1. Reliability

Reliability refers to the stability of the test (Carter, Godoy, Marakovitz and Briggs-Gowan, 2009). In

order for an audiological test to be reliable the test should consist of controlled stimuli in an acoustically-controlled environment (Frank & Rosen, 2007). All patients in this study were tested using the Interacoustics Eclipse System for ABR testing and a GSI 61 audiometer for behavioural

testing, both calibrated and serviced annually, thus technical inconsistencies were minimized. Daily biologic calibration was conducted by the audiologist before using all equipment as per Departmental Protocol, which ensures the accuracy of the equipment (Frank & Rosen, 2007). All

testing rooms were also sound-treated to reduce noise.

Owing to the fact that this study is a retrospective record review, controlling patient variables to a high degree of reliability could not be ensured. The testing conditions remained the same in each

test to the best of the tester’s ability. According to Carter et al. (2009), a detailed training manual and assessment protocol increases inter-rater reliability. All patients were tested with the same protocol, written by the researcher, thus maximizing reliability. Patient and test variables were

39 | P a g e

thought to also be managed by the fact that the behavioural audiometry and ABR testing procedures

form part of standard audiology practice for qualified audiologists (Kanji, 2010).

The ABR test has established test-retest reliability (Song, Nicol & Kraus, 2011). Similarly, intra-subject reliability is small in that variations in the absolute latency of the click ABR differ very little between tests (Song et al., 2011). Therefore, results from the ABR test will give a reliable indication of the

patient’s hearing abilities.

2.6.2. Validity

Validity refers to the ability of a test to measure what it purports to measure (Carter et al., 2009). Validity was enhanced by taking into consideration the effect of patient and environmental factors

on ABR tracings. According to the ABR protocol utilized at CHBAH, “noisy tracings” (or those tracings for which the signal-to-noise ratio is worse than 3:1) are deleted, and another tracing is conducted. In this way, the response is replicable, and clearer deductions can be made.

Panacek (2007) recommends that in order to increase the validity of a retrospective review,

variables should be defined before data is abstracted. Each patient had been diagnosed with a neurological disorder by a relevant professional before their ABR test, and this diagnosis was copied from the patient’s hospital file by the tester. Degree of hearing loss was classified for each patient

according to the classification by Gelfand (2009) (see Appendix 1). In this way the abstraction from the data records was consistent (Panacek, 2007).

Similarly, Panacek (2007) states that a uniform data collection form should be utilized in order to enhance the validity of the study. All patient data was captured onto a summary form (see Appendix

40 | P a g e

2.6.3. Bias

ABR interpretation is subjective, as the tester has to identify waveforms in order to make a diagnosis. In order to reduce bias, the interpretation of the ABR waveforms was taken as written on

the patient report. The waveforms for each child were interpreted by the tester at the time of the test. The diagnosis written on the page was taken, thus results were analyzed by one of five audiologists and not just the author.

2.7. Ethical Considerations

Permission to review records was obtained from CHBAH hospital management and the Head of Department of Speech Therapy and Audiology at CHBAH (see Appendices 3 and 4). Data collection only began following permission from the Postgraduate Review Committee, and the Human Research Ethics Committee (Medical) at the University of the Witwatersrand. The Ethical Clearance

Certificate Number M120217 (see Appendix 5) was obtained on 24.02.2012. All of this was in accordance with the World Medical Association (WMA) Declaration of Helsinki (2008), which calls for

all medical research to appear before an Ethics Committee.

Owing to the fact that it is a retrospective study of patient records, patient consent was not obtained. However, these patients attended a teaching and research hospital where records are utilized for research purposes. According to the WMA Declaration of Helsinki (2008), no harm should come to the patient. All subjects in this study sample attended CHBAH for a hearing test during

which the patient was not harmed in any way. No additional intervention occurred for the purpose of this study.

41 | P a g e

Similarly, the WMA Declaration of Helsinki (2008) states that patient privacy should be ensured, and that no personal information should be divulged. A coding system was created whereby patients

were allocated a number so that no identifying information was utilized. This ensured confidentiality and anonymity of the study sample. Therefore, this study abides by the ethical regulations of confidentiality and non-maleficence.

The WMA Declaration of Helsinki (2008) additionally states that testing should only be conducted by

appropriately trained personnel. All testing conducted for the patient records was performed by audiologists working at CHBAH and registered with the HPCSA to practice audiology.

Justice is a major consideration in medical ethics (Pratt & Loff, 2011). Justice is defined differently in

various sources, and consists of ensuring that the research conducted reacts to the health needs and priorities of the community or country in which it was conducted, that all benefits are fairly and freely available to participants during and after clinical trials, and result in the strengthening of

ethical research in the community or country of the research participants (Pratt & Loff, 2011). This research project adhered to the principle of justice in that, as evident in the literature review above, neurological disorders are rife in the paediatric population of South Africa, and thus comprise the burden of disease in this population.

Similarly, all patients had undergone ABR testing, thus no treatment options were withheld and all patients received equal opportunities in terms of hearing testing options. By adhering to these aspects of justice, this research contributes to an ethically-sound body of medical studies.

42 | P a g e

3. Results

3.1. Demographic Profile

A total of 40 patient files were drawn from the Departmental Archive. All patients resided in the catchment area for Chris Hani Baragwanath Academic Hospital in Soweto, Johannesburg. The sample consisted of 21 males and 19 females. The average age was 28 months, with a standard deviation of 24 months. The median age was 22 months, and the age range was 5 months to 115 months (9 years

7 months).

Results are described per ear for audiological analyses (N = 80), and per participant in analyzing the pathologies (N = 40). Certain patients had multiple neurological disabilities. For these patients all

relevant diagnoses were taken into account in analysis if the disability appeared on the above list of neurological disabilities for this study. Eleven children presented with two neurological disabilities and five further children had been diagnosed with three of the neurological disabilities included in

this study.