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Despite the preferred approach to early detection, it is important to highlight the advantages and limitations of each approach in light of the context in which the NHS programme is to be implemented.

Implementation of UNHS has shown to decrease the age of diagnosis of hearing impairment (Durieux-Smith, Fitzpatrick, & Whittingham, 2008; Ghogomu, Umansky, & Lieu, 2014), which may in turn lead to earlier intervention and its associated positive outcomes in terms of early childhood development. UNHS further facilitates detection of hearing impairment in infants without risk factors who may otherwise be missed. Of the 709 children in the study by Durieux-Smith et al. (2008), 128 (of whom 124 presented with risk factors) had been identified through UNHS or TNHS programmes and the remaining 581 had been referred by a physician. Children who were screened through either of the NHS programmes were diagnosed significantly earlier (mean age of diagnosis at 6.3 months) than those with risk factors who were referred (mean age of diagnosis at 34.5 months). In comparison to the children without risk factors, those with risk factors were diagnosed earlier. Despite differences in ages at diagnosis, only 21 of the 128 children who underwent NHS had a confirmed diagnosis and received intervention by three and six months of age, respectively. Durieux-Smith and colleagues (2008) propose that this may be due to other medical conditions taking priority over the identification of hearing impairment in those admitted to the neonatal intensive care unit. Similar findings in terms of a significant decrease in the age of diagnosis of unilateral sensorineural hearing impairment were also reported in a retrospective record review conducted at a single site in Missouri in the United States (Ghogomu et al., 2014). Findings from this study indicated that the mean age of detection of hearing impairment decreased from 4.4 years to 2.6 years of age with an increase in the rate of detection from 3 percent to 26 percent by six months of age.

While the overall benefits of UNHS are evident, there are limitations to this approach as well. First, less severe congenital hearing impairment (less than 30–40dB) is often not detected in UNHS programmes. The second limitation is related to UNHS programmes using a two-step screening protocol in which low-risk infants with auditory neuropathy may not be detected by the use of OAEs as the only screening measure (Patel et al., 2011).

Similarly, one of the most commonly reported TNHS limitations is that it may result in missed cases of hearing impairment. Between 25 and 50 percent of infants with hearing impairment may not be identified if only TNHS is utilised, and babies without risk factors for hearing impairment may be at risk of being identified late (Durieux-Smith & Whittingham, 2000; Hyde, 2005; Kountakis, Skoulas, Phillips, & Chang, 2002). ‘The percentage of babies missed may be due to the absence of hearing impairment in those with risk factors and the presence of hearing impairment in those without risk factors’ (Kanji, 2016, p. 51). However, despite these limitations, it is important to consider the context in which TNHS is conducted, as the proportion of neonates or infants with risk factors may be greater in some contexts than in others. TNHS may be a beneficial, interim screening method in LAMI countries where the recommendation of UNHS appears rather overwhelming or is not yet feasible. The development of an appropriate and contextually relevant HRR documenting the risk factors for hearing impairment may also assist in highlighting the cases that require monitoring and follow-up (Johnson, 2002).

Irrespective of the choice of approach, there is cost involved in implementation:

For NHS programmes, costs are incurred for all those screened, but the benefits are experienced by only a small percentage of neonates. The most important variables to include in such an analysis are the actual costs of the screening, the effectiveness of the screening, the prevalence of hearing impairment and the cost consequences associated with preventing, treating or managing hearing impairment. Assessment of benefits must then include both the health and economic benefits associated with preventing, treating or managing hearing impairment. (World Health Organization [WHO], 2010, p. 10)

The cost-effectiveness of UNHS and TNHS has been explored in eight different provinces in China (Huang et al., 2012) using the guidelines stipulated by the WHO (2010). UNHS was found to be more cost-effective when there was a good coverage rate in terms of the total number of newborns and infants screened, diagnosed and enrolled into an intervention programme. TNHS, on the other hand, was more feasible in provinces where all these rates were low. In order to improve TNHS in these provinces, Huang et al. (2012) recommended that pilot surveys be conducted to determine the context-specific risk factors for permanent congenital and early onset hearing loss. A systematic review by Colgan et al. (2012) suggested that the cost-effectiveness of UNHS can only be concluded if longer-term costs and outcomes associated with such programmes are accounted for.

A cost-effectiveness comparison of UNHS and selective screening (TNHS) of newborns with pre-specified risk factors was conducted by Burke, Shenton, and Taylor (2012) between a high-income and a LAMI country (United Kingdom and India). TNHS yielded a better positive predictive value (Burke et al., 2012). UNHS incurred more costs than TNHS as a result of a larger number of false positive findings. Costs may therefore be viewed as relative to the prevalence of hearing impairment in each region, with higher costs in regions with a lower prevalence as more infants need to be tested in order to detect those with hearing impairment (Burke et al., 2012). It may therefore be argued that the costs incurred in LAMI countries may be lower as that is where the prevalence of hearing impairment is reported to be higher in comparison to higher-income countries (Kanji, 2016).