Grading and Evaluating Hearing Loss

Classification and Evaluation Methods

• The American Academy of Otolaryngology-Head and Neck Surgery recommends pure tone audiometry as the gold standard for grading hearing loss, measuring hearing thresholds at specific frequencies to determine the degree and configuration of hearing loss 1
• Normal hearing is typically defined as ≤20 dB HL, according to the American Academy of Otolaryngology-Head and Neck Surgery 1, 2
• A complete hearing assessment should include pure tone audiometry, which measures air and bone conduction thresholds at frequencies from 250-8000 Hz, as recommended by the American Academy of Otolaryngology-Head and Neck Surgery 1, 3
• The American Academy of Otolaryngology-Head and Neck Surgery suggests that tympanometry is essential for evaluating middle ear function 1, 4
• Acoustic reflex testing is recommended by the American Academy of Otolaryngology-Head and Neck Surgery to assess neural pathways 1, 2

Specialized Grading Systems

• The Chang Grading System is particularly useful for evaluating cisplatin-induced ototoxicity in children, with grades ranging from 0 to 4 based on hearing thresholds at specific frequencies, as described in the Journal of Clinical Oncology 5, 6
• The Brock Grading System is used primarily for cisplatin-induced hearing loss, with grades ranging from 0 to 4 based on hearing thresholds at specific frequencies, as described in the Journal of Clinical Oncology 5, 6

Age-Specific Testing Methods

• The American Academy of Pediatrics recommends age-appropriate testing methods for children, including auditory brainstem response (ABR) and otoacoustic emissions (OAEs) for infants under 6 months, visual reinforcement audiometry for children 6 months to 2 years, play audiometry for children 2-4 years, and conventional audiometry for children 4+ years 4
• The American Academy of Otolaryngology-Head and Neck Surgery suggests that testing for age-related hearing loss (presbycusis) should include frequencies most affected by presbycusis (typically high frequencies) 1, 2

Important Considerations

• The American Academy of Otolaryngology-Head and Neck Surgery emphasizes the importance of distinguishing between sensorineural hearing loss, conductive hearing loss, and mixed hearing loss 1
• Baseline audiometry should be performed before treatment with potentially ototoxic medications, and serial monitoring should be conducted during and after treatment, as recommended by the Journal of Clinical Oncology 5, 6

Diagnostic Evaluation of Hearing Loss

Components of Comprehensive Audiometric Evaluation

• The American Academy of Otolaryngology-Head and Neck Surgery recommends that a comprehensive diagnostic evaluation for hearing loss should include pure tone thresholds, which measure hearing sensitivity through both air conduction and bone conduction pathways 7, 8
• Air and bone conduction thresholds should be measured at frequencies from 250-8000 Hz, and mid-octave frequencies (750, 1500, 3000, 6000 Hz) should be tested if differences between adjacent octave frequencies are ≥20 dB 8
• Speech audiometry assesses functional hearing ability, including speech recognition threshold (SRT) or speech detection threshold, and word recognition scores (WRS) measured at suprathreshold levels 7, 8, 9

Clinical Value of Pure Tone Audiometry

• Pure tone audiometry (PTA) provides critical diagnostic information that guides treatment decisions, including establishing the pattern of hearing loss at various frequencies, differentiating the degree of hearing loss, and determining the configuration/type of hearing loss 7
• PTA provides baseline measurements for monitoring changes over time, and enables appropriate treatment planning based on specific hearing deficits 7, 10, 11

Limitations and Considerations

• Access to audiometric testing may be limited in some regions, with 56.6% of US counties lacking access to audiologists 7, 12
• Older adults may have difficulty completing testing due to cognitive dysfunction, and standard test-retest variability typically fluctuates by ±5 dB across frequencies 7, 12

Alternative Screening Methods

• Automated audiometry can be considered as a secondary alternative when comprehensive audiometry is not immediately available, and app-based or online testing options exist but have moderate evidence quality compared to standard PTA 12, 8, 9, 10

Special Considerations

• For asymmetric hearing loss, conductive/mixed hearing loss, or poor word recognition, referral to an otolaryngologist is recommended 7, 13

Hearing Loss Classification and Management

Functional Hearing Status

• The American Academy of Otolaryngology-Head and Neck Surgery classifies hearing loss based on decibel hearing levels, with a functional impact that can be understood in terms of percentage impairment, and hearing aids are appropriate and beneficial for individuals with usable or serviceable hearing, classified as Class B/C, according to the AAO-HNS classification 14
• The AAO-HNS serviceable hearing classification includes Class B, with PTA 31-50 dB and discrimination 50-69%, and Class C, with PTA >50 dB and discrimination 50-69%, both of which are considered usable hearing 14

Hearing Loss Classification and Diagnosis

Degree of Hearing Loss

• The American Academy of Otolaryngology-Head and Neck Surgery classifies moderate hearing loss as 41-55 dB HL 15
• The American Academy of Otolaryngology-Head and Neck Surgery classifies moderately severe hearing loss as 56-70 dB HL, severe hearing loss as 71-90 dB HL, and profound hearing loss as >90 dB HL 16

Screening Pitfalls and Variability

• Standard test-retest variability typically fluctuates by ±5 dB across frequencies, so changes <10 dB may not represent true threshold shifts, according to the American Academy of Otolaryngology-Head and Neck Surgery [15] [16]

Monitoring Ototoxicity

• The American Society of Clinical Oncology recommends baseline audiometry before treatment with cisplatin or other ototoxic medications, with serial monitoring during and after treatment 17

Normal Hearing Range and Age-Related Changes

Baseline Normal Hearing Range

• The normal human ear can process sound frequencies from 20 to 20,000 Hz across the lifespan, with 500 to 4000 Hz being the most critical range for speech processing, as recommended by the American College of Physicians 18
• The speech-critical frequency range is 500 to 4000 Hz, which is essential for understanding conversation and communication, according to the American Academy of Otolaryngology-Head and Neck Surgery 18
• For children, normal hearing is defined as ≤15 dB HL at the 3-frequency pure tone average (500, 1000, 2000 Hz), as defined by the American Academy of Otolaryngology-Head and Neck Surgery 19, 20

Age-Related Changes in Hearing Range

• The prevalence of hearing loss ranges from 20% to 40% in adults older than 50 years, increasing to more than 80% in adults aged 80 years or older, as reported by the American College of Physicians 18
• High-frequency hearing above 8000 Hz deteriorates more rapidly with age, while speech-frequency hearing (500-4000 Hz) may remain relatively preserved until later decades, according to the American College of Physicians 18

Clinical Testing Frequencies

• Primary care screening typically focuses on 500, 1000, 2000, and 4000 Hz using a fail criterion of >20 dB HL at one or more frequencies, as recommended by the American Academy of Otolaryngology-Head and Neck Surgery 19

Important Clinical Caveats

• Children under age 3 years have "normal thresholds" that are up to 15 dB greater than older children due to developmental effects and testing methodology limitations, as defined by the American Academy of Otolaryngology-Head and Neck Surgery 20

Air‑Bone Gap Measurement and Clinical Application

Definition and Standard Measurement

• The air‑bone gap (ABG) is quantified as the difference between air‑conduction and bone‑conduction thresholds in decibels (dB), not as a percentage, because the dB scale directly reflects the magnitude of conductive impairment. American Academy of Otolaryngology‑Head and Neck Surgery recommends this approach. 21
• ABG (dB) = Air‑Conduction Threshold (dB HL) − Bone‑Conduction Threshold (dB HL) at each test frequency. 21
• Air‑conduction thresholds should be obtained across the frequency range 250 Hz – 8000 Hz. 21
• Bone‑conduction thresholds should be obtained across the frequency range 250 Hz – 4000 Hz. 21

Clinical Significance and Decision‑Making

• Decibel‑based ABG values are used to determine the need for medical or surgical intervention for conductive pathology; the absolute dB magnitude, rather than a relative percentage, guides treatment planning. American Academy of Otolaryngology‑Head and Neck Surgery. 21
• Established hearing‑loss grading systems (e.g., Chang, Brock, CTCAE) employ absolute dB thresholds for classification and do not use percentage‑based calculations. 22

Assessment When Bone‑Conduction Testing Is Unavailable

• Conductive hearing loss can be distinguished from sensorineural loss using air‑conduction audiometry together with tympanometry to verify normal middle‑ear function. American Academy of Otolaryngology‑Head and Neck Surgery. 21

Ototoxicity and Sensorineural Grading Considerations

• When grading ototoxicity or sensorineural hearing loss, any conductive component must be excluded by confirming normal tympanograms or by obtaining bone‑conduction thresholds. 22
• If only air‑conduction data are available, clinicians must first ensure normal middle‑ear status with tympanometry before applying sensorineural grading criteria. 22