Early Identification of HL Flashcards
Why is HL an “important health problem” that warrants screening?
- Unrecognized HL in young children compromises the development of speech and language
- Could consider impaired hearing as a primary health condition (cochlea= primary sense organ)
- HL is a causal or mediator variable that along with other factors can have a strong influence on long-term language outcomes
What is the prevalence of congenital HL in developed countries and high-risk populations?
- Congenital HL: 1-3/1000 (.2-.3%) in developed countries
- 1-2% in “high risk” populations (~10x that of the general newborn population)
Describe OAEs as a screening test.
- Some variation in OAE detectability
- Vulnerable to minor CHL
Describe ABRs as a screening test.
- Strong relationship between detectability of ABR and audibility of transient sound
- Unlike OAE, can be used to directly estimate thresholds. However, process can be time consuming
- Not as susceptible to minor middle ear disorders but is affected by disorders that reduce or abolish temporal synchrony of the stimulus-evoked action potential
- In screening context, specific stimulus and recording parameters are applied to yield a binary decision regarding ABR presence or absence
What are some limitations of OAE & ABR as screening tests?
- Don’t have intrinsic validity
- Responses may be observed consistently in absence of behavioral response to sound and behavioral responses may be observed in the absence of response - Errors due to environmental noise, physiological noise, natural biological variations in response amplitude (inaccuracy)
What is sensitivity?
-the probability of a positive test when the disorder is truly present
What is specificity?
-the probability of a negative test when the disorder is truly absent
Describe OAE & ABR screening sensitivity.
- Sensitivities of DPOAE, TEOAE, and ABR are ~0.6-0.65 (not really that acceptable)
- Could be influenced by:
- Difference in ABR stimuli
- Screening stimulus level (nHL vs. HL)
Describe OAE & ABR screening specificity.
- Very well understood
- Must information available re: specificity because population prevalence of HL is low
- The vast majority of babies who fail the initial screen will not have HL
- Overall proportion of babies who fail is generally an accurate estimate of the screen false positive rate given a substantial sample size that is relatively easy to obtain
What could possibly cause false positives in OAE & ABR screening?
- Random algorithmic error
- High environmental noise (AOAEs)
- High electromyogenic noise (AABR)
- Partially blocked probe/insert
- Naturally small OAEs/ABRs
- Minor middle ear conditions (AOAEs)
- Substantial transient conductive loss (AABR)
- Suboptimal test methods
What is “case definition” in hearing screening programs?
-Most current programs target permanent HL of 30-40 dB or greater
Describe the protocols and equipment in screening programs.
- Most manufacturers target HL of 40 dB HL or greater
- Automated ABR and OAEs are the primary test methods used in NBHS
- OAEs may be preferred for hospitals with dedicated personnel who can become proficient at probe placement
- Costs make ABR prohibitive
Describe follow-up procedures after screening.
- 1, 3, 6 benchmarks
- Knowing method used to screen is important so that outpatient re-screen is the same
- Must have a mechanism in place for communicating with parents and PCPs as well as prompt referral to EI
- Familiarization of funding sources for amplification
- Employ EBP
What did Yoshinago-Itano et al. (1998) state about NBHS?
-Provided evidence that children whose HL was identified early and received early intervention before 6 months of age had better language outcomes
What did Norton et al. (2000) find about NBHS?
-TEOAEs, DPOAEs, and ABR have similar abilities to identify HL of 30 dB or greater as assessed by subsequent VRA at 8-12 months corrected age
