Practical ABR Screening Pass Criterion for 6-Month-Old Infants
For ABR screening in 6-month-old infants, the pass criterion is the presence of an identifiable and replicable Wave V response at 30 dB nHL (or 35 dB nHL) in both ears. 1, 2
Standard Pass Criteria
The American Academy of Pediatrics guideline establishes that automated ABR screening uses a 30 dB nHL click stimulus as the standard screening level 1. An infant passes when:
- Wave V is present and replicable at 30-35 dB nHL bilaterally
- The response must be identifiable in both ears independently
- Each ear is tested separately with insert earphones or ear inserts 1
Research confirms this threshold: one study specifically defined pass criteria as "an identifiable and replicable wave V response present at 30 dB HL in both ears" 2, while another used 35 dB nHL as the pass criterion 3.
Important Clinical Considerations at 6 Months
At 6 months of age, sedation is often required because infants at this age are typically too active to remain sufficiently quiet during testing 1. The guideline explicitly states that diagnostic ABR "is performed in children in natural sleep up to approximately 3 to 6 months of age and then under sedation for older infants" 1.
Key Testing Parameters:
- Stimulus: Click stimuli delivered through insert earphones
- Intensity level: 30-35 dB nHL for screening
- Response criterion: Presence of Wave V
- Test duration: Approximately 15 minutes 1
- Electrode placement: On the infant's head to detect neurologic response 1
Critical Pitfalls to Avoid
Do not interpret absence of Wave V at screening levels as definitive hearing loss without considering maturational factors. Research demonstrates that ABR responses are strongly related to postconceptual age, and many "failures" in younger infants result from immaturity rather than true hearing loss 4. However, by 6 months chronological age, maturation should be sufficient for reliable testing.
If an infant fails at 30 dB nHL, test at higher intensities (50 dB and 69 dB nHL) to determine severity 5. The pattern of response helps categorize hearing loss:
- Absent response at 30-60 dB nHL = mild to moderate hearing impairment 2
- Absent response at 70 dB nHL = severe to profound hearing impairment 2
Follow-Up Algorithm
Any failure at 30 dB nHL requires immediate referral to a pediatric audiologist for comprehensive diagnostic ABR 1. The diagnostic ABR differs from screening by:
- Testing multiple frequencies with tone bursts (not just clicks)
- Creating a frequency-specific hearing map similar to an audiogram
- Including bone conduction testing to differentiate conductive from sensorineural loss 1
Air-conduction hearing threshold levels greater than 20 dB at any frequency indicate possible hearing loss and mandate audiologic referral 1.
State and Environmental Requirements
The infant must remain quiet and relatively inactive during testing 1. Factors that can affect test quality include:
- Infant state (quiet sleep is optimal versus crying) 5
- Recording noise levels
- Electrode impedance
- Testing site ambient noise 5
Ensure proper electrode placement and low impedance to minimize the number of sweeps needed and reduce test time 5.