Extended scope of practice audiology in the ENT outpatient clinic - a pilot study.

OBJECTIVE: To investigate the feasibility of using an extended scope (ES) audiology service to provide care to non-urgent adult patients waiting for an Ear Nose and Throat (ENT) appointment. DESIGN: Based on suitability criteria developed by the Audiology and ENT departments, an internal review of the ENT wait list identified patients who would be suitable for an ES audiology clinic. STUDY SAMPLE: 220 non-urgent patients on the ENT wait list with hearing loss and/or tinnitus. RESULTS: A total of 220 patients were transferred from the ENT wait list to the ES audiology clinic: 200 (90.9%) were seen by the ES Audiologist and 20 (9.1%) patients self-discharged or did not attend the appointment. Out of the 200 patients seen, 175 (87.5%) were assessed, managed and discharged without the need for input from an Otologist. The remaining 25 (12.5%) patients needed an Otologist's input. CONCLUSION: This study has demonstrated the feasibility of an ES audiology clinic in a tertiary teaching hospital. Of those seen by ES audiologist, 87.5% were discharged from the ENT wait list without medical intervention. This model may represent an effective alternative pathway for lengthy outpatient waiting list management whilst providing patients with timely access to care.

Audiology practice during COVID-19 crisis in Jordan and Arab countries.

OBJECTIVE: This study investigated audiologists' knowledge of COVID-19 characteristics and infection control measures they followed during the COVID-19 pandemic. Moreover, it examined the impact of COVID-19 on audiology practice, and audiologist's knowledge of telehealth as an alternative. DESIGN: A web-based cross-sectional study using a questionnaire consisting of four sections. STUDY SAMPLE: This study engaged 164 audiologists practicing in Jordan and Arab countries. RESULTS: Fever, cough, difficulty in breathing, and fatigue were identified as COVID-19 characteristics by over 80% of the audiologists. Other symptoms were identified by less than half of the audiologists. The audiologists showed limited knowledge regarding measures against COVID-19 transmission. This study revealed the limited availability of infection control measures in many audiologists' workplace. The majority of audiologists stopped working due to the COVID-19 crisis and only 61.6% of the audiologists were familiar with the concepts of tele-audiology and its related aspects. However, most participants were keen to learn more. CONCLUSIONS: This study revealed limited knowledge among audiologists regarding some of the COVID-19 characteristics, and limited compliance with the infection control policies. Limited knowledge in the application of telehealth in audiology practice was also shown.

Common Audiological Functional Parameters (CAFPAs) for single patient cases: deriving statistical models from an expert-labelled data set.

Objective: Statistical knowledge about many patients could be exploited using machine learning to provide supporting information to otolaryngologists and other hearing health care professionals, but needs to be made accessible. The Common Audiological Functional Parameters (CAFPAs) were recently introduced for the purpose of integrating data from different databases by providing an abstract representation of audiological measurements. This paper aims at collecting expert labels for a sample database and to determine statistical models from the labelled data set.Design: By an expert survey, CAFPAs as well as labels for audiological findings and treatment recommendations were collected for patients from the database of Hörzentrum Oldenburg.Study sample: A total of 287 single patient cases were assessed by twelve highly experienced audiological experts.Results: The labelled data set was used to derive probability density functions for categories given by the expert labels. The collected data set is suitable for estimating training distributions due to realistic variability contained in data for different, distinct categories. Suitable distribution functions were determined. The derived training distributions were compared regarding different audiological questions.Conclusions: The method-expert survey, sorting data into categories, and determining training distributions - could be extended to other data sets, which could then be integrated via the CAFPAs and used in a classification task.

Cochrane corner: platinum-induced hearing loss after treatment for childhood cancer.

This Cochrane Corner features the review entitled "Platinum-induced hearing loss after treatment for childhood cancer" published in 2016. In their review, van As et al. identified 13 cohort studies including 2837 participants with a hearing test after treatment with a platinum-based therapy for different types of childhood cancers. All studies had problems related to quality of the evidence. The reported frequency of hearing loss varied between 1.7% and 90.1% for studies that included a definition of hearing loss; none of the studies provided data on tinnitus. Only two studies evaluated possible risk factors. One study found a higher risk of hearing loss in people treated with the combination of cisplatin plus carboplatin compared to treatment with cisplatin only and for exposure to aminoglycosides. The other found that age at treatment (lower risk in older children) and single maximum cisplatin dose (higher risk with an increasing dose) were significant predictors for hearing loss, while gender was not. This systematic review shows that children treated with platinum analogues are at risk of developing hearing loss, but the exact prevalence and risk factors remain unclear.

Common Audiological Functional Parameters (CAFPAs): statistical and compact representation of rehabilitative audiological classification based on expert knowledge.

OBJECTIVE: As a step towards objectifying audiological rehabilitation and providing comparability between different test batteries and clinics, the Common Audiological Functional Parameters (CAFPAs) were introduced as a common and abstract representation of audiological knowledge obtained from diagnostic tests. DESIGN: Relationships between CAFPAs as an intermediate representation between diagnostic tests and audiological findings, diagnoses and treatment recommendations (summarised as "diagnostic cases") were established by means of an expert survey. Expert knowledge was collected for 14 given categories covering different diagnostic cases. For each case, the experts were asked to indicate expected ranges of diagnostic test outcomes, as well as traffic light-encoded CAFPAs. STUDY SAMPLE: Eleven German experts in the field of audiological rehabilitation from Hanover and Oldenburg participated in the survey. RESULTS: Audiological findings or treatment recommendations could be distinguished by a statistical model derived from the experts' answers for CAFPAs as well as audiological tests. CONCLUSIONS: The CAFPAs serve as an abstract, comprehensive representation of audiological knowledge. If more detailed information on certain functional aspects of the auditory system is required, the CAFPAs indicate which information is missing. The statistical graphical representations for CAFPAs and audiological tests are suitable for audiological teaching material; they are universally applicable for real clinical databases.

Early prelingual auditory development in Italian infants and toddlers analysed through the Italian version of the Infant-Toddler Meaningful Auditory Integration Scale (IT-MAIS).

PURPOSE: To evaluate the reliability and validity of the Italian version of the Infant-Toddler Meaningful Auditory Integration Scale (I-IT-MAIS), and to assess the normal trajectory of early prelingual auditory (EPLAD) development from birth to 24 months in a group of normal-hearing Italian children using the I-IT-MAIS. METHODS: The study consisted of four phases: item generation, reliability analysis, assessment of the normal trajectory for EPLAD, and validity analysis. A group of 120 normal-hearing children and a group of 31 deaf children wearing hearing aids and on a waiting list for cochlear implantation were enrolled. All the parents completed the I-IT-MAIS. Sixty of them completed the I-IT-MAIS twice, 2 weeks apart, for test-retest reliability analysis. The I-IT-MAIS scores were used to assess the normal trajectory of EPLAD development from birth to 24 months in normal-hearing children. For criterion validity analysis, the I-IT-MAIS scores were correlated with production of infant scale evaluation (PRISE) scores in 60 normal-hearing children. For discriminant validity analysis, the I-IT-MAIS scores obtained in normal and deaf children were compared. RESULTS: Internal consistency of I-IT-MAIS was satisfactory as well as individual item reliability, test-retest reliability, and discriminant validity. EPLAD development in normal-hearing Italian-speaking children was evaluated. As far as the criterion validity of the I-IT-MAIS is concerned, a strong correlation between I-IT-MAIS and PRISE scores was found. CONCLUSION: I-IT-MAIS is reliable and valid. Its application is recommended for clinical practice and outcome research.

Further validation of the Chinese (Mandarin) Tinnitus Handicap Inventory: comparison between patient-reported and clinician-interviewed outcomes.

OBJECTIVE: The objective of this study was to evaluate the feasibility of the Chinese (Mandarin) Tinnitus Handicap Inventory (THI-C) by comparing patient-reported and clinician-interviewed outcomes and to raise awareness of the difficulties in using adapted international test measures. DESIGN: All patients were required to first complete the THI-C independently. Then, clinicians conducted a face-to-face interview, explained the exact meaning of each item and re-evaluated every item based on the patient's descriptions. During this process, patients were encouraged to make comments about each item. Both the self-administered and clinician-interviewed scores were recorded and compared. STUDY SAMPLE: A total of 178 patients who reported tinnitus as a primary complaint were included. RESULTS: Among these patients, 88 (49.4%) completed the questionnaire independently, while 79 (44.4%) patients experienced difficulty in understanding at least one item. The difference between the self-administered and clinician-interviewed scores was statistically significant (p < 0.01). CONCLUSIONS: The feasibility of the THI-C is limited unless a revision is made. Follow-up studies are needed for validation when a newly translated self-administered questionnaire is put into use. In addition to semantic equivalence and idiomatic equivalence, experiential equivalence and conceptual equivalence should also be fully considered during the translation process.

A method for determining precise electrical hearing thresholds in cochlear implant users.

OBJECTIVE: A psychoacoustic procedure designed for the precise assessment of perceptional threshold (T-level) in cochlear implant (CI) users is presented. The impact of this procedure on speech perception was investigated. DESIGN: Individual T-level measurements were obtained with the proposed procedure and three different speech processor fitting conditions were applied: (1) fitting familiar to the subject, T-levels unchanged, (2) T-level set to thresholds determined with the new procedure, (3) T-level set to thresholds determined with the new procedure, but T-level is decreased by 10 clinical units (CU). The impact of the different fitting conditions was measured by means of categorical loudness scaling (CLS) and speech perception tests in quiet and noise. STUDY SAMPLE: A prospective study at a tertiary referral university hospital. 18 experienced postlingually deafened cochlear implanted adult subjects. RESULTS: Average sound-field thresholds obtained by CLS were lowest in condition using the new procedure yielding a larger dynamic range with significantly higher speech scores in quiet compared to those with a subject's commonly used programme, and significantly improved in noise even after reducing T-levels by 10 CU. CONCLUSION: The precise determination of T-levels by means of the proposed procedure improved performance in several speech recognition tasks. Compared to the default behavioural setting, T-level increased on median by 9 CU. Average speech reception threshold in noise for soft speech levels (50 dB sound pressure level) decreased by 1 dB.

Costs and effectiveness of hearing conservation programs at 14 US metal manufacturing facilities.

OBJECTIVE: This study characterised overall and specific costs associated with hearing conservation programmes (HCPs) at US metal manufacturing sites, and examined the association between these costs and several noise-induced hearing loss (NIHL) outcomes. DESIGN: We interviewed personnel and reviewed records at participating facilities. We also measured noise for comparison to the ten-year average of measurements made by each facility. NIHL outcomes assessed included rates of standard threshold shifts (STS) and high-frequency hearing loss, as well as prevalence of hearing impairment, for each participating facility. We used linear regression to identify per-person HCP costs that best predicted the NIHL outcomes. STUDY SAMPLE: We evaluated 14 US metal manufacturing facilities operated by a single company. RESULTS: Annual HCP costs ranged from roughly $67,000 to $397,000 (average $308 ± 80 per worker). Our full-shift noise measurements (mean 83.1 dBA) showed good agreement with the facilities' measurements (mean 82.6 dBA). Hearing impairment prevalence was about 15% overall. Higher expenditures for training and hearing protector fit-testing were significantly associated with reduced STS prevalence. Higher training expenditures were also related to lower hearing impairment prevalence and high-frequency hearing loss rates. CONCLUSIONS: HCP costs were substantial and variable. Increased workplace spending on training and fit-testing may help minimise NIHL.

Ototoxicity monitoring through the eyes of the treating physician: Perspectives from pulmonology and medical oncology.

OBJECTIVES: Integrating audiological management into the care pathways of clinical specialties that prescribe ototoxic medications for essential, often life-preserving medical care that is critical for early hearing loss identification and remediation. Research shows that successful implementation of a new health service or intervention requires alignment of goals among provider groups, institutional leadership and patients. Thoughtful consideration of the physician's viewpoints about ototoxicity and its implications for treatment planning is, therefore, important for the implementation and enduring success of an ototoxicity monitoring programme (OMP). DESIGN: This discussion paper uses qualitative methods to explore the perspectives of four physicians on OMP provision in their patient populations. STUDY SAMPLE: Three pulmonologists and one oncologist completed the written survey or survey-based interview described in this report. RESULTS: Each physician indicated that (i) ototoxicity is a potential problem for their patients; (ii) monitoring hearing is important to ensure good quality of life among their patients and (iii) treatment modification would be considered if an alternative treatment option were available. The physicians differed in their approaches to ototoxicity monitoring, from routine referrals to audiology, to relying on patient self-referral. CONCLUSION: Physician provider input is needed to optimise monitoring schedules and OMP care coordination with audiology.

Competing agendas and other tensions in developing patient-centred communication in audiology education: a qualitative study of educator perspectives.

OBJECTIVE: Patient-centred communication (PCC) is an essential skill for effective healthcare provision and is accepted as a core competency in medicine and allied health. In audiology, recent studies have shown that audiologists rarely display PCC in adult hearing interactions. This highlights a need to investigate how PCC is taught and learnt in audiology. There is a paucity of studies on PCC in audiology education. The aim of this study is to examine educator perceptions of teaching PCC, including barriers and facilitators, in Australian graduate audiology programmes. DESIGN: Semi-structured interviews were conducted with audiology educators responsible for communication training. Interview transcripts were analysed using qualitative content analysis. STUDY SAMPLE: Nine participants, including programme coordinators and key teaching staff from all six Australian audiology programmes participated in the study. RESULTS: PCC education was found to be influenced by four emerging themes: professional culture and values, contextual factors, knowledge and understanding of PCC and individual factors. CONCLUSIONS: These results provide an insight into the competing agendas involved in implementing PCC education in both the university and clinical component of audiology programmes. The findings can play a role in refining and building the evidence-base for teaching and facilitating patient-centred audiological care in future audiologists.

Applying U.S. national guidelines for ototoxicity monitoring in adult patients: perspectives on patient populations, service gaps, barriers and solutions.

OBJECTIVES: To promote establishment of effective ototoxicity monitoring programs (OMPs), this report reviews the U.S. national audiology guidelines in relation to "real world" OMP application. Background is provided on the mechanisms, risks and clinical presentation of hearing loss associated with major classes of ototoxic medications. DESIGN: This is a non-systematic review using PubMed, national and international agency websites, personal communications between ototoxicity experts, and results of unpublished research. Examples are provided of OMPs in various healthcare settings within the U.S. civilian sector, Department of Defense (DoD), and Department of Veterans Affairs (VA). STUDY SAMPLE: The five OMPs compared in this report represent a convenience sample of the programs with which the authors are affiliated. Their opinions were elicited via two semi-structured teleconferences on barriers and facilitators of OMP, followed by a self-administered questionnaire on OMP characteristics and practices, with responses synthesized herein. Preliminary results are provided from an ongoing VA clinical trial at one of these OMP sites. Participants were 40 VA patients who received cisplatin chemotherapy in 2014-2017. The study arms contrast access to care for OMP delivered on the treatment unit versus usual care as provided in the audiology clinic. RESULTS: Protocols of the OMPs examined varied, reflecting their diverse settings. Service delivery concerns included baseline tests missed or completed after the initial treatment, and monitoring tests done infrequently or only after cessation of treatment. Perceived barriers involved logistics related to accessing and testing patients, such as a lack of processes to help patients enter programs, patients' time and scheduling constraints, and inconvenient audiology clinic locations. Use of abbreviated or screening methods facilitated monitoring. CONCLUSIONS: The most effective OMPs integrated audiological management into care pathways of the clinical specialties that prescribe ototoxic medications. More OMP guidance is needed to inform evaluation schedules, outcome reporting, and determination of actionable ototoxic changes. Guidance is also lacking on the use of hearing conservation approaches suitable for the mass testing needed to support large-scale OMP efforts. Guideline adherence might improve with formal endorsement from organizations governing the medical specialty stakeholders in OMP such as oncologists, pulmonologists, infectious disease specialists, ototolaryngologists and pharmacists.

Use of noise cancellation earphones in out-of-booth audiometric evaluations.

OBJECTIVE: To assess the utility of noise cancelation earphones (NCE) in audiometric evaluations. DESIGN: Degree of noise reduction of Bose QuietComfort 15 NCE was assessed through probe-microphone measures and sound-field audiometry. Occlusion effects from NCE were assessed for potential effects on bone-conduction thresholds. STUDY SAMPLE: Twenty participants were tested to determine average occlusion effect values during bone-conduction testing with and without NCE. Noise reduction values of the NCE were assessed on a single subject through probe-microphone measures and sound-field testing. RESULTS: NCE sufficiently reduced ambient noise to levels acceptable for air-conduction testing as well as for bone-conduction testing for most patients when adding minimal adjustment to acceptable levels as outlined by the ANSI S3.1-1999 standard. In addition, NCE did not create a clinically significant change in the occlusion effect for bone-conduction testing. CONCLUSION: NCE placed over insert earphones provide a sound pressure level at the tympanic membrane that is below ANSI standards for routine air-conduction testing and result in sufficient ambient noise reduction for bone-conduction testing with most patients. There is no clinically significant occlusion effect from NCE during routine bone-conduction audiometry. These findings support the utility of using NCE for offsite audiometric testing.

Characteristics of children with unilateral hearing loss.

OBJECTIVE: The purpose of this study was to describe the clinical characteristics of children with unilateral hearing loss (UHL), examine deterioration in hearing, and explore amplification decisions. DESIGN: Population-based data were collected prospectively from time of diagnosis. Serial audiograms and amplification details were retrospectively extracted from clinical charts to document the trajectory and management of hearing loss. SAMPLE: The study included all children identified with UHL in one region of Canada over a 13-year period (2003-2015) after implementation of universal newborn hearing screening. RESULTS: Of 537 children with permanent hearing loss, 20.1% (108) presented with UHL at diagnosis. They were identified at a median age of 13.9 months (IQR: 2.8, 49.0). Children with congenital loss were identified at 2.8 months (IQR: 2.0, 3.6) and made up 47.2% (n = 51), reflecting that a substantial portion had late-onset, acquired or late-identified loss. A total of 42.4% (n = 39) showed deterioration in hearing, including 16 (17.4%) who developed bilateral loss. By study end, 73.1% (79/108) of children had received amplification recommendations. CONCLUSIONS: Up to 20% of children with permanent HL are first diagnosed with UHL. About 40% are at risk for deterioration in hearing either in the impaired ear and/or in the normal hearing ear.

The development of the University of Jordan word recognition test.

OBJECTIVE: To develop and validate a digitally recorded speech test battery to assess speech perception in Jordanian Arabic-speaking adults. DESIGN: Selected stimuli were digitally recorded and were divided into four lists of 25 words each. Speech audiometry was completed for all listeners. Participants were divided into two equal groups of 30 listeners each with equal male to female ratio. The first group of participants completed speech reception thresholds (SRTs) and word recognition testing on each of the four lists using a fixed intensity. The second group of listeners was tested on each of the four lists at different intensity levels in order to obtain the performance-intensity function. STUDY SAMPLE: Sixty normal-hearing listeners in the age range of 19-25 years. All participants were native speakers of Jordanian Arabic. RESULTS: Results revealed that there were no significant differences between SRTs and pure tone average. Additionally, there were no differences across lists at multiple intensity levels. CONCLUSIONS: In general, the current study was successful in producing recorded speech materials for Jordanian Arabic population. This suggests that the speech stimuli generated by this study are suitable for measuring speech recognition in Jordanian Arabic-speaking listeners.

Wideband acoustic immittance in children with Down syndrome: prediction of middle-ear dysfunction, conductive hearing loss and patent PE tubes.

OBJECTIVE: The purpose of this study was to evaluate pressurised wideband acoustic immittance (WAI) tests in children with Down syndrome (DS) and in typically developing children (TD) for prediction of conductive hearing loss (CHL) and patency of pressure equalising tubes (PETs). DESIGN: Audiologic diagnosis was determined by audiometry in combination with distortion-product otoacoustic emissions, 0.226 kHz tympanometry and otoscopy. WAI results were compared for ears within diagnostic categories (Normal, CHL and PET) and between groups (TD and DS). STUDY SAMPLE: Children with DS (n = 40; mean age 6.4 years), and TD children (n = 48; mean age 5.1 years) were included. RESULTS: Wideband absorbance was significantly lower at 1-4 kHz in ears with CHL compared to NH for both TD and DS groups. In ears with patent PETs, wideband absorbance and group delay (GD) were larger than in ears without PETs between 0.25 and 1.5 kHz. Wideband absorbance tests were performed similarly for prediction of CHL and patent PETs in TD and DS groups. CONCLUSIONS: Wideband absorbance and GD revealed specific patterns in both TD children and those with DS that can assist in detection of the presence of significant CHL, assess the patency of PETs, and provide frequency-specific information in the audiometric range.

Tympanometric measurements in conscious sheep - a diagnostic tool for pre-clinical middle ear implant studies.

OBJECTIVE: To investigate and establish the use of tympanometry in conscious sheep to provide a means of objective assessment of tympanic membrane integrity, middle ear ventilation and functioning of the Eustachian tube (ET). DESIGN: After conditioning the sheep for four weeks, tympanometric measurements at 226 Hz were carried out weekly for 13 weeks. Before measurements, the external ear canal had been cleaned. Resultant curves were classified according to human reference values. STUDY SAMPLE: Tests were performed on 12 female blackface sheep. RESULTS: After cleaning of the external ear canal under otoscopic control, tympanic membranes were intact with no evidence of acute or chronic middle ear inflammation, middle ear effusion or retraction. Cleaning ensured valid, objective and reproducible measurements. As the majority of normal tympanograms were notched without the appearance of any malformation, an additional tympanogram type (AN) was introduced. The notched appearance can most likely be explained by the anatomy of the middle ear of the sheep and the test frequency that was used. CONCLUSION: The current study demonstrated how tympanometry can be used to evaluate treatment modalities for middle ear and ET function in conscious sheep. This provided a large animal model for further human research in otology.

Auditory adaptation testing as a tool for investigating tinnitus origin: two patients with vestibular schwannoma.

OBJECTIVE: To enhance the understanding of tinnitus origin by disseminating two case studies of vestibular schwannoma (VS) involving behavioural auditory adaptation testing (AAT). DESIGN: Retrospective case study. STUDY SAMPLE: Two adults who presented with unilateral, non-pulsatile subjective tinnitus and bilateral normal-hearing sensitivity. At the initial evaluation, the otolaryngologic and audiologic findings were unremarkable, bilaterally. Upon retest, years later, VS was identified. RESULTS: At retest, the tinnitus disappeared in one patient and was slightly attenuated in the other patient. In the former, the results of AAT were positive for left retrocochlear pathology; in the latter, the results were negative for the left ear although a moderate degree of auditory adaptation was present despite bilateral normal-hearing sensitivity. Imaging revealed a small VS in both patients, confirmed surgically. CONCLUSION: Behavioural AAT in patients with tinnitus furnishes a useful tool for exploring tinnitus origin. Decrease or disappearance of tinnitus in patients with auditory adaptation suggests that the tinnitus generator is the cochlea or the cochlear nerve adjacent to the cochlea. Patients with unilateral tinnitus and bilateral, symmetric, normal-hearing thresholds, absent other audiovestibular symptoms, should be routinely monitored through otolaryngologic and audiologic re-evaluations. Tinnitus decrease or disappearance may constitute a red flag for retrocochlear pathology.

Insights on different analysis techniques in the monothermal and bithermal caloric test - which parameter should we use to quantify vestibular function?

OBJECTIVE: To investigate the use of maximum slow component velocity (MSCV) and time-constant duration (TCd) of elicited nystagmus in quantifying the caloric response and to assess the efficacy of these parameters in the monothermal screening test. DESIGN: Retrospective analysis of caloric results obtained from 150 patients. Bithermal unilateral weakness (UW), directional preponderance (DP), monothermal caloric asymmetry (MCA) based on warm or cool irrigations only, were calculated using both MSCV and TCd. STUDY SAMPLE: 66 males and 84 females, aged 16-88 years (µ = 50, σ = 17), who underwent vestibular assessment. RESULTS: The correlation-coefficient between bithermal caloric unilateral weaknesses calculated using either MSCV or TCd is 0.155 (p < 0.01). Using MSCV and setting significant MCA at 10%, the sensitivity and specificity were respectively 100% and 34% for monothermal warm and 82% and 53% for monothermal cool tests. Using TCd and setting significant MCA at 5%, the sensitivity and specificity were respectively 90% and 77% for monothermal warm and 100% and 74% for monothermal cool tests. CONCLUSIONS: In the monothermal warm caloric test, MSCV can be used more reliably than monothermal cool to predict normal bithermal caloric response. The reverse is true if using TCd. Unilateral-weakness calculated using TCd and MSCV were poorly correlated and therefore likely to be demonstrating different aspects of vestibular function.

Average optimal DPOAE primary tone levels in normal-hearing adults.

OBJECTIVE: Despite great progress towards optimizing DPOAE primary tone characteristics, factors such as stimulus and intra-subject emission variability have not been addressed. The purpose of this study was to identify optimal primary tone level relationships when these sources of variability were acknowledged, and to identify any influences of test frequency. DESIGN: Following coupler-based measurements assessing primary tone level stability, two experiments were conducted. In experiment 1, DPOAE test-retest reliability without probe replacement was measured for f2 = 1-6 kHz with L1 = L2 = 65 dB SPL. In experiment 2, optimal L1-L2 relationships were identified for f2 = 1-6 kHz. For 20 ≤ L2 ≤ 75 dB SPL, L1 was varied 15 dB SPL above and below the recommendation of L1 = 0.4 L2 + 39 [dB SPL]. STUDY SAMPLE: Eleven normal-hearing adults participated in experiment 1. Thirty normal-hearing adults participated in experiment 2. RESULTS: Stimulus variability did not exceed 0.1 dB SPL. DPOAE reliability testing revealed an across-frequency mean standard error of measurement of 0.52 dB SPL. The average optimal L1-L2 relationship was described by L1 = 0.49 L2 + 41 [dB SPL]. A significant effect of frequency was identified for 6 kHz. CONCLUSION: Including relevant sources of variability improves internal validity of a primary tone level optimization formula.