What is the standard method for grading hearing loss?

Standard Methods for Grading Hearing Loss

Pure tone audiometry (PTA) is the gold standard for grading hearing loss, measuring hearing thresholds at specific frequencies to determine the degree (mild, moderate, severe, or profound) and configuration of hearing loss. 1

Classification Systems for Hearing Loss

General Hearing Loss Classification

Hearing loss is typically graded based on pure tone thresholds measured in decibels hearing level (dB HL):

• Normal hearing: ≤20 dB HL 1
• Mild hearing loss: 21-40 dB HL 1, 2
• Moderate hearing loss: 41-55 dB HL 2
• Moderately severe hearing loss: 56-70 dB HL 3
• Severe hearing loss: 71-90 dB HL 3
• Profound hearing loss: >90 dB HL 3

Specialized Grading Systems

Chang Grading System

Particularly useful for evaluating cisplatin-induced ototoxicity in children:

• Grade 0: ≤20 dB at 1,2, and 4 kHz 1
• Grade 1a: ≥40 dB at any frequency 6-12 kHz 1
• Grade 1b: >20 and <40 dB at 4 kHz 1
• Grade 2a: ≥40 dB at 4 kHz and above 1
• Grade 2b: >20 and <40 dB at any frequency below 4 kHz 1
• Grade 3: ≥40 dB at 2 or 3 kHz and above 1
• Grade 4: ≥40 dB at 1 kHz and above 1

Brock Grading System

Used primarily for cisplatin-induced hearing loss:

• Grade 0: <40 dB at all frequencies 1
• Grade 1: ≥40 dB at 8 kHz 1
• Grade 2: ≥40 dB at 4 kHz and above 1
• Grade 3: ≥40 dB at 2 kHz and above 1
• Grade 4: ≥40 dB at 1 kHz and above 1

Comprehensive Audiometric Evaluation Components

A complete hearing assessment should include:

• Pure tone audiometry: Measures air and bone conduction thresholds at frequencies from 250-8000 Hz 1
• Speech audiometry: Includes speech recognition threshold (SRT) and word recognition scores (WRS) 1, 4
• Tympanometry: Evaluates middle ear function 1
• Acoustic reflex testing: Assesses neural pathways 1

Important Considerations in Hearing Assessment

Type of Hearing Loss

It's crucial to distinguish between:

• Sensorineural hearing loss: Inner ear or nerve pathway damage 1, 3
• Conductive hearing loss: Outer or middle ear obstruction 1, 3
• Mixed hearing loss: Combination of both types 1, 3

Age-Specific Testing Methods

• Infants and young children: May require specialized testing such as auditory brainstem response (ABR), otoacoustic emissions (OAEs), or play audiometry 1
• Children 2-4 years: Play audiometry is most appropriate 1
• Children 4+ years and adults: Conventional audiometry 1

Clinical Pitfalls to Avoid

• Failing to distinguish conductive from sensorineural loss: Bone conduction testing is essential to differentiate these types 1
• Ignoring high-frequency hearing loss: Testing should include frequencies up to 8000 Hz, as high-frequency loss often occurs first 2
• Relying solely on automated testing: While app-based or automated testing can be useful for screening, they should not replace comprehensive audiometric evaluation 1, 5
• Overlooking middle ear pathology: Tympanometry should be performed to rule out middle ear dysfunction 1

Special Considerations for Specific Populations

Ototoxicity Monitoring

For patients receiving potentially ototoxic medications (e.g., cisplatin, aminoglycosides):

• Baseline audiometry should be performed before treatment 1
• Serial monitoring should be conducted during and after treatment 1
• Specialized grading systems like Chang or Brock should be used to track changes 1

Pediatric Assessment

Children require age-appropriate testing methods:

• Under 6 months: ABR and OAEs are primary tools 1
• 6 months to 2 years: Visual reinforcement audiometry 1
• 2-4 years: Play audiometry 1
• 4+ years: Conventional audiometry 1

Elderly Patients

For age-related hearing loss (presbycusis):

• Testing should include frequencies most affected by presbycusis (typically high frequencies) 1
• Word recognition testing is particularly important as speech discrimination often deteriorates 1, 4