Ototoxicity: A Challenge in Diagnosis and Treatment

Serum Per- and Polyfluoroalkyl Substances Are Associated with Increased Hearing Impairment: A Re-Analysis of the National Health and Nutrition Examination Survey Data

Although studies have shown that per- and polyfluoroalkyl substances (PFAS) are potential environmental ototoxicants, epidemiologic study has been limited. I conducted a cross-sectional study to re-examine the associations between PFAS and hearing impairment. Data were obtained from the National Health and Nutrition Examination Survey (NHANES) 1999–2000, 2003-06, 2009-12, and 2015-16. Perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) were measured in serum samples. Participants were divided into quartiles for each PFAS. Air conduction pure-tone audiometry was administered. Hearing impairment (1: yes, 0: no) was defined as a hearing threshold of more than 25 dB at 500, 1000, 2000, 4000, and 8000 Hz in the worse ear. I assessed the relation of serum PFAS with hearing impairment by the generalized linear mixed model with a logit link and binary distribution. Tests for linear trend across quartiles of serum PFAS were conducted using the median serum PFAS in each quartile as a continuous variable. After adjusting for age, sex, body mass index, education, ethnicity group, and family income, I found positive correlations between PFOA and hearing impairment at 2000 Hz (p-trend < 0.01) and 3000 Hz (p-trend = 0.02); between PFOS and hearing impairment at 500 Hz (p-trend < 0.01), 2000 Hz (p-trend < 0.0001) and 3000 Hz (p-trend = 0.02); between PFNA and hearing impairment at 2000 Hz (p-trend = 0.05), 3000 Hz (p-trend < 0.01), 4000 Hz (p-trend = 0.02), and 8000 Hz (p-trend < 0.01); between PFHxS and hearing impairment at 500 Hz (p-trend = 0.04), 1000 Hz (p-trend = 0.03), and 2000 Hz (p-trend < 0.01). However, some of the findings were not significant when only comparing the highest with the lowest quartile of PFASs. In conclusion, several background serum PFASs are positively correlated with hearing impairment in the United States adult population.

What Are the Current Audiological Practices for Ototoxicity Assessment and Management in the South African Healthcare Context?

The study was an initial exploration of the current ototoxicity assessment and management practices by audiologists in South Africa. An exploratory survey research methodology through a cross-sectional research design was adopted where audiologists were recruited from professional associations' databases in South Africa, using specific inclusion criteria. The study made use of an 18-item web-based survey guided by the Health Professions Council of South Africa (HPCSA) (2018) guidelines which were developed from reviewing international guidelines such as the American Speech-Language-Hearing Association (ASHA,1994) and the American Academy of Audiology (AAA, 2009). The study surveyed 31 audiologists from across the country. Data were analyzed through descriptive statistics. Findings implied significant gaps between knowledge and translation of this knowledge into practice. Over two thirds of the participants engage with ototoxicity monitoring and management, but the practices adopted by them do not align with international standards nor with the national HPCSA guidelines on assessment and management of patients on ototoxic medications. Most participants do not conduct baseline assessments, and the frequency of monitoring is irregular and reduced from the recommended; thus influencing ability for early detection and intervention of ototoxicity within this context. Non-standard assessment battery is used for assessment and monitoring, raising questions about the reliability and validity of the data used to make preventive treatment decisions. Lack of collaborative work between audiologists and the rest of the clinical team involved in the treatment of patients on ototoxic medications was found to be an important contributing factor to the less than optimal ototoxicity management practices. Of factors potentially influencing adherence to guidelines, the institution of employment, specifically employment in a tuberculosis hospital, seemed to have a positive influence, possibly due to the focused nature of the audiologists' scope of practice there as well as availability of resources. The level of education appeared to have no influence. Current findings provide contextually relevant evidence on ototoxicity assessment and management within this context. They raise important implications for guidelines adherence and translating knowledge, policies and guidelines into practice, clinical assessment and management protocols followed, appropriate resource allocation per programme, as well as strategic planning for national ototoxicity assessment and management programmes in context. The findings also raise important implications for low- and middle-income countries, in terms of adopting international guidelines without considering context.

Chemicals, noise and occupational hearing health in South Africa: A mapping study

BACKGROUND

Chemical exposure leading to ototoxicity is a fresh challenge for occupational healthcare in South Africa.

OBJECTIVES

The critical question is: 'what is known about occupational ototoxic chemicals with or without noise exposure in South Africa?'

METHOD

This qualitative, mapping study was completed with published (peer-reviewed) and grey literature from 1979-2019. Data was analysed using the Preferred Reporting Items for Systematic reviews and Meta-Analyses: extension for Scoping Reviews and the Nursing and Allied Health Resources Section subcommittee on Mapping the Literature of Nursing and Allied Health (adapted). Numerical analysis of article type was completed, but the primary focus was on capturing patterns/trends using thematic analysis and ideology critique.

RESULTS

The African Journal of Disability, African Journal of Primary Health Care and Family Medicine, South African Medical Journal, The South African Journal of Communication Disorders [SAJCD] and Health SA Gesondheid) were included with the SAJCD containing one relevant item and seventeen other items were analysed. Research focusses on the mining sector (gold) in Gauteng, and ototoxic medication (tuberculosis and/or human immunodeficiency virus) take precedence. In KwaZulu-Natal, the focus is on commerce and industry across formal and informal sectors. There are no governmental policies that refer to chemical ototoxicity. Occupational hearing loss is configured exclusively on the meme that noise exposure is the only toxin.

CONCLUSION

Chemical exposures are only just beginning to be recognised as ototoxic in South Africa. Hearing conservation programmes should always serve the workers' interests and never bow down to the econometric interests of employers.

Drug-induced hearing loss: a case/non-case study in the French pharmacovigilance database

Hearing loss is defined as a decrease in the ability to perceive sounds which can occur suddenly or gradually and affects one ear or both. It is related to various etiologies, in particular drugs. The identification of all drugs that could be associated with hearing loss is essential for the patients' life quality. The objective of our study was to identify signals of hearing loss involving drugs approved in the last 20 years. The occurrence in association with drugs known for their ototoxicity was also analyzed. We used a case/non-case method in the French Pharmacovigilance Database (FPVD). The cases were reports of hearing loss in the FPVD between January 2007 and August 2017. Non-cases were all reports over the same period. We calculated the reporting odds ratio (ROR) with 95% confidence intervals. Among the 555 reports of hearing loss, significant RORs were found for 68 drugs. The main therapeutic classes implicated were antineoplastic agents (n = 240), systemic anti-infective agents (n = 182), immunosuppressants (n = 42) loop diuretics (n = 26), and salicylate analgesics (n = 26). We found signals of hearing loss with azacitidine, vaccines and nevirapine, immunosuppressants such as leflunomide, and biotherapies such as panitumumab and vandetanib. Prescribers should be informed about the potential associations with all these drugs. The role of the pathology itself and the known ototoxic drugs that can be associated do not allow to conclude definitively. Audiograms for the early detection of hearing loss induced by drugs known to be ototoxic are rarely carried out. Preventive treatments exist and must be considered.

An Ototoxicity Grading System Within a Mobile App (OtoCalc) for a Resource-Limited Setting to Guide Grading and Management of Drug-Induced Hearing Loss in Patients With Drug-Resistant Tuberculosis: Prospective, Cross-Sectional Case Series

BACKGROUND

Tuberculosis (TB) affects millions of people worldwide and is treated with medication including aminoglycosides and polypeptides. Individuals respond differently to medications as a result of their genetic inheritance. These differences in genetic inheritance can result in the underdosing or overdosing of medication, which may affect the efficacy or, in the case of aminoglycosides and polypeptides used in the treatment of all forms of TB, result in ototoxicity. When ototoxicity is detected, physicians should adjust dosages to minimize further ototoxicity and hearing loss; however, there are no suitable grading systems to define significant hearing loss.

OBJECTIVE

The aim of this study was to develop a standardized grading system by making use of an electronic health (eHealth) platform to ensure that a user-friendly method was available to interpret hearing test results, calculate significant hearing loss, and provide recommendations with regard to dosage adjustments and management. It further aimed to establish the sensitivity of the newly developed grading scale.

METHODS

This grading system was developed in South Africa based on data that were obtained from an audiology and pharmacokinetic study on patients with drug-resistant TB (DR-TB) at two DR-TB units at state-run hospitals. This feasibility study employed a prospective, cross-sectional, exploratory, descriptive case series research design, with a total of 22 participants. Participants underwent audiological and pharmacological assessments at baseline and every 2 weeks for the first 3 months of treatment. Various professionals (8 in total) were subsequently involved in the development of the eHealth system, including a software engineer, four audiologists, a pharmacist, a medical doctor, and a nurse. The app underwent 14 modifications that involved aspects of data storage, ease of usability, grades, and the risk factor checklist.

RESULTS

An ototoxicity grading system within a mobile app for use by doctors, nurses, and audiologists was developed for patients with DR-TB. The purpose of this user-friendly ototoxicity calculator, OtoCalc, is to (1) assist health professionals in assessing patients for ototoxicity, (2) establish the clinical significance of ototoxicity by calculating the grade of hearing loss, (3) monitor the progression of hearing loss, and (4) enable systematic referral and management of patients according to their needs.

CONCLUSIONS

This newly developed system is more sensitive than the existing grading methods for determining ototoxicity in patients with DR-TB. This app needs to be trialed in a larger sample to establish data security, ease of use, and suitability within this population.

Auditory, video head impulse test and vestibular evoked myogenic potentials findings in adults with human immunodeficiency virus

OBJECTIVES

Even though there is an association between hearing loss and human immunodeficiency virus (HIV), particularly in low- and middle-income countries, further research is needed to investigate the nature of such hearing loss. Likewise, despite documented vestibular alterations in people with HIV, the true occurrence, presentation, and nature of these manifestations are yet to be established. Advances in technology for vestibular testing has allowed for objective site-of-lesion tests such as the video head impulse test (vHIT), cervical vestibular evoked myogenic potentials (cVEMPs) and ocular vestibular evoked myogenic potential (oVEMPs). The current study aimed to compare and describe auditory, vHIT, cVEMPs and oVEMPs findings in adults with and without HIV.

METHODS

The current study included an HIV positive group (n = 30) and an HIV negative group (n = 30) who underwent an auditory assessment (tympanometry and pure tone audiometry) and objective vestibular assessments.

RESULTS

The occurrence of hearing loss was 53.3% in the HIV positive group compared to 33.3% in the HIV negative group. A higher occurrence of vestibular involvement was documented in the HIV positive group (73.3%) compared to 13.3% in the HIV negative group.

CONCLUSION

Auditory assessment and objective measures of vestibular end-organ function (vHIT and VEMPs) can be useful to detect sub-clinical alterations. The equipment is mobile and can be performed in any health care setting such as infectious disease clinics for surveillance and monitoring purposes.

Ototoxic Adverse Drug Reactions: A Disproportionality Analysis Using the Italian Spontaneous Reporting Database

Introduction: The panorama of drug-induced ototoxicity has widened in the last decades; moreover, post-marketing data are necessary to gain a better insight on ototoxic adverse drug reactions (ADRs). The aim of this study was to perform an analysis of ADR reports describing drug-induced ototoxicity from the Italian spontaneous reporting system (SRS).

Methods: As a measure of disproportionality, we calculated the reporting odds ratios (RORs) and 95% confidence intervals (CIs) with a case/non-case methodology. Cases were all suspected ADR reports regarding drug-induced ototoxicity collected into the Italian SRS from 2001 to 2017. Non-cases included all other ADRs reported in the same period.

Results: Of 325,980 reports, 652 included at least one ototoxic ADR, compared with 325,328 non-cases. Statistically significant adjusted RORs were found for drugs for cardiovascular disorders, urologicals, teriparatide, amikacin, prulifloxacin, rifampicin and isoniazid, cisplatin, hormone antagonists, tacrolimus, pomalidomide, tramadol, and antidepressants. Significant adjusted RORs in relation to tinnitus were also observed for doxazosin (ROR 5.55, 95% CI 2.06–14.93), bisoprolol (4.28, 1.59–11.53), nebivolol (8.06, 3.32–19.56), ramipril (3.96, 2.17–7.23), irbesartan (19.60, 9.19–41.80), betamethasone (4.01, 1.28–12.52), moxifloxacin (4.56, 1.71–12.34), ethambutol (12.25, 3.89–38.57), efavirenz (16.82, 5.34–52.96), sofosbuvir/ledipasvir (5.95, 1.90–18.61), etoposide (7.09, 2.63–19.12), abatacept (6.51, 2.42–17.53), indometacin (6.30, 2.02–19.72), etoricoxib (5.00, 2.23–11.23), tapentadol (4.37, 1.09–17.62), and timolol combinations (23.29, 9.53–56.95). Moreover, significant adjusted RORs for hypoacusis regarded clarithromycin (3.95, 1.86–8.40), azithromycin (10.23, 5.03–20.79), vancomycin (6.72, 2.14–21.11), methotrexate (3.13, 1.00–9.81), pemetrexed (4.38, 1.40–13.76), vincristine (5.93, 1.88–18.70), vinorelbine (21.60, 8.83–52.82), paclitaxel (2.34, 1.03–5.30), rituximab (3.20, 1.19–8.63), interferon alfa-2b (17.44, 8.56–35.53), thalidomide (16.92, 6.92–41.38), and deferasirox (41.06, 20.07–84.01).

Conclusions: This study is largely consistent with results from literature. Nevertheless, propafenone, antituberculars, hormone antagonists, teriparatide, tramadol, and pomalidomide are unknown for being ototoxic. Hypoacusis after the use of vinorelbine, methotrexate, and pemetrexed is unexpected, such as tinnitus related with etoposide, nebivolol, betamethasone, abatacept, sofosbuvir/ledipasvir, and tapentadol, but these considerations require further investigation to better define the risk due to the paucity of data. Moreover, physicians should be aware of the clinical significance of ototoxicity and be conscious about the importance of their contribution to spontaneous reporting.

Ototoxicity: Visualized in Concept Maps

Ototoxicity refers to the damage to structures and function of the auditory-vestibular system caused by exogenous agents such as pharmaceuticals, chemicals, and ionizing radiation. There are many potentially ototoxic substances. For example, depending on how ototoxicity is defined, there are 200 to 600 medications that can cause damage to hearing and/or balance. Ototoxicity encompasses cochleotoxicity, vestibulotoxicity, and neurotoxicity. A variety of professional disciplines are involved in determining causation, prevention, and management of ototoxic effects. Research to identify and develop otoprotectants and otorescue agents is emerging and will translate basic scientific discovery into applications for use in hearing conservation programs, safety operations, and clinical care. Original concept maps are presented here to visually represent knowledge pathways, domains, and relationships essential to the understanding of ototoxicity.

Monitoring Protocols for Cochlear Toxicity

The need for monitoring hearing and auditory function during drug therapy and other treatments that have the potential to cause hearing loss is well documented. Besides the main purpose of ototoxic monitoring, which is to provide feedback to the attending physician about the effects the treatment is having on the auditory system, it is also helpful in setting expectations for the patient and his/her family about the communication issues that may result from the drug therapy. This article will review tests available to an audiologist, both subjective and objective, that can be used to effectively monitor hearing levels and auditory function during treatment. Published guidelines and various ototoxic monitoring protocols are reviewed regarding tests administered, what constitutes a significant change in test results and how these findings are reported, and the impact significant changes may have on the course of treatment. Test protocols from different institutions are compared for both similarities and contrasts. Effective scheduling and test location are key to a successful monitoring program. Finally, the need to streamline ototoxic monitoring of hearing and auditory function to reduce test time and make it less stressful and tiresome on the patient will be considered.

[Drug-induced hearing loss as a manifestation of drug-induced ototoxicity]

The ability of drugs to have an ototoxic effect has been studied for a long time, however, the true prevalence of this undesirable phenomenon is unknown, which is due to the use of various audiological protocols, a wide range of reactions to drugs in different ethnic groups, and most importantly, the lack of caution with regard to otological symptoms due to their reversibility or lack of immediate threat to life. Drug-induced ototoxicity is a functional disorder of the inner ear (cochlea and/or vestibular apparatus) or eighth pair of cranial nerves. Pharmacotherapy, associated with the development of ototoxic drug reactions, may remain undervalued for a long time, often until irreversible hearing impairment is formed. The most frequently prescribed drugs that cause ototoxic phenomena include anticancer drugs, antibacterial drugs of the aminoglycoside group, loop diuretics, calcium channel blockers, non-steroidal anti-inflammatory drugs, antimalarial drugs, salicylates, etc. Monitoring the degree of hearing impairment before and during therapy is important in preventing the development of drug-induced ototoxicity and makes it possible to consider alternative treatment regimens in a timely manner. It is in this connection that the role of participation in the appointment of rational pharmacotherapy to patients with a potential risk of developing otological phenomena of a clinical pharmacologist and audiologist undoubtedly increases.