Classification of Hearing Loss Severity
The American College of Medical Genetics and Genomics (ACMG) 2022 guideline establishes the standard six-tier classification system for hearing loss severity based on decibel thresholds: slight (16-25 dB), mild (26-40 dB), moderate (41-55 dB), moderately severe (56-70 dB), severe (71-90 dB), and profound (≥91 dB). 1, 2
Standard ACMG Classification System
The ACMG framework provides the most authoritative and granular approach to categorizing hearing loss severity:
Slight hearing loss: 16-25 dB 1, 2
- May go unrecognized but can impact communication in challenging listening environments 2
Mild hearing loss: 26-40 dB 1, 2
- Difficulty with conversations in noisy environments 2
Moderate hearing loss: 41-55 dB 1, 2
- Difficulty maintaining conversations without hearing aids 2
Moderately severe hearing loss: 56-70 dB 1, 2
- Requires powerful hearing aids and reliance on lip reading 2
Severe hearing loss: 71-90 dB 1, 2
- Significant functional impairment requiring advanced amplification 1
Profound hearing loss: ≥91 dB 1, 2
- May require cochlear implantation for optimal outcomes 3
Normal Hearing Threshold
- Normal hearing is defined as ≤20 dB HL 2
- Thresholds between 0-15 dB represent optimal hearing function 2
Critical Clinical Application Points
The classification must be applied to the better-hearing ear to accurately reflect functional hearing status. 2 This is essential because:
- Bilateral asymmetric hearing loss should be staged based on the better ear's thresholds 2
- The better ear determines functional communication ability and treatment planning 2
The ACMG six-tier system is more precise than older three-tier classifications that omit "slight" and "moderately severe" categories, providing superior granularity for clinical decision-making and genetic counseling. 2
Impact on Clinical Outcomes
The severity classification directly determines:
- Treatment selection: Hearing aids versus cochlear implants 3
- Quality of life outcomes: Severity correlates with ADL/IADL impairment and SF-36 scores 4
- Communication function: QuickSIN performance deteriorates systematically with increasing severity in sensorineural hearing loss 5
- Rehabilitation intensity: More severe losses require more aggressive intervention 2
Common Pitfalls to Avoid
- Do not classify based on the worse ear when hearing is asymmetric—always use the better ear 2
- Do not assume slight hearing loss (16-25 dB) is clinically insignificant—it can meaningfully impact communication in challenging environments 2
- Do not conflate severity classification with functional impact—two patients with identical audiometric thresholds may have vastly different speech-in-noise performance, particularly with sensorineural loss 5
- Do not use severity classification alone to determine candidacy for amplification—functional measures like speech-in-noise testing add critical information beyond pure-tone thresholds 5