Low cost calibrated mechanical noisemaker for hearing screening of neonates in resource constrained settings.

Background & objectives: There is a need to develop an affordable and reliable tool for hearing screening of neonates in resource constrained, medically underserved areas of developing nations. This study valuates a strategy of health worker based screening of neonates using a low cost mechanical calibrated noisemaker followed up with parental monitoring of age appropriate auditory milestones for detecting severe-profound hearing impairment in infants by 6 months of age. Methods: A trained health worker under the supervision of a qualified audiologist screened 425 neonates of whom 20 had confirmed severe-profound hearing impairment. Mechanical calibrated noisemakers of 50, 60, 70 and 80 dB (A) were used to elicit the behavioural responses. The parents of screened neonates were instructed to monitor the normal language and auditory milestones till 6 months of age. This strategy was validated against the reference standard consisting of a battery of tests - namely, auditory brain stem response (ABR), otoacoustic emissions (OAE) and behavioural assessment at 2 years of age. Bayesian prevalence weighted measures of screening were calculated. Results: The sensitivity and specificity was high with least false positive referrals for 70 and 80 dB (A) noisemakers. All the noisemakers had 100 per cent negative predictive value. 70 and 80 dB (A) noisemakers had high positive likelihood ratios of 19 and 34, respectively. The probability differences for pre- and post- test positive was 43 and 58 for 70 and 80 dB (A) noisemakers, respectively. Interpretation & conclusions: In a controlled setting, health workers with primary education can be trained to use a mechanical calibrated noisemaker made of locally available material to reliably screen for severe-profound hearing loss in neonates. The monitoring of auditory responses could be done by informed parents. Multi-centre field trials of this strategy need to be carried out to examine the feasibility of community health care workers using it in resource constrained settings of developing nations to implement an effective national neonatal hearing screening programme.

Efficacy of a low cost protocol in reducing noise levels in the neonatal intensive care unit.

Objective. To examine the effectiveness and cost of implementing a noise reduction protocol in a level III neonatal intensive care unit (NICU). Methods. A prospective longitudinal study was done in a level III NICU, wherein a noise reduction protocol that included behavioral and environmental modification was implemented. The noise levels were measured sequentially every hour for 15 days before and after this intervention. The statistical significance of the reduction in noise levels after implementation of the protocol was tested by paired sample student's t-test. Cost was calculated using the generalized cost effectiveness model of the World Health Organisation. The present study has 80 % power with 95 % confidence to measure 2 dB differences between groups for the maximum recommended of 50 dB. Results. The protocol in the present study reduced noise levels in all the rooms of the NICU to within 60 dB with high statistical significance (p< 0.001). The extent of noise reduction in the rooms of the NICU was as follows : ventilator room by 9.58 dB (95 % confidence interval: 6.73 – 12.42, p < 0.001) , stable room by 6.54 dB (95 % confidence interval: 2.92 – 4.16 , p < 0.001), isolation room by 2.26 dB (95 % confidence interval: 1.21 – 3.30, p < 0.001) , pre-term room by 2.37 dB(95 % confidence interval: 1.22 – 3.51, p < 0.001)and extreme preterm room by 2.09 dB (95 % confidence interval: 1.14 – 3.02, p < 0.001). The intervention was most cost-effective in the ventilator room, requiring Rs. 81.09 to reduce 1 dB and least effective in the extreme pre-term room requiring Rs. 371.61 to reduce 1 dB. Conclusion. The high efficacy and affordability of noise reduction protocols justify the need for implementation of these measures as a standard of care in neonatal intensive care units.