Study area and design
The data used in the study came from two surveys conducted in 2012 and 2018 by the National Center for Birth Defects Monitoring of China. The data in the 2012 survey covered the period from 2008 to 2010, while the data in the 2018 survey covered the year 2016. The surveys were reviewed and approved by National Health Commission of the People’s Republic of China with an national administrative notice was transmitted before each survey. All related medical institutions reported the tabulated data accordingly, which did not involve individual information, and the ethics approval and consent to participate were not necessary in the study.
The two surveys included all licensed medical institutions providing NHS or diagnosis of congenital hearing impairment in China. The 2012 survey included 7,001 institutions that provided NHS and 116 that diagnosed infant hearing impairment, which were located in 30 provinces comprising 1,657 districts/counties. The 2018 survey included 11,875 institutions that provided NHS and 214 that diagnosed impairment, located in 31 provinces comprising 2,664 districts/counties (Appendix 1).
A uniform questionnaire was used to collect data on live births, initial screening rates (total and failed), secondary screening rates (total and failed), and rates of hearing impairment diagnosis among infants who failed secondary screening.
For each county/district, designated maternal and child health institutions collected data in their respective jurisdictions and reported the data to municipal- and provincial-level maternal and child health institutions for quality control. The audited questionnaires were then reported to the National Center for Birth Defects Monitoring (Figure 1). The National Center checked the data and interviewed staff in charge of NHS and infant hearing impairment diagnosis at 45 medical institutions in three provinces to further confirm the correctness of the data.
NHS was defined as well-born babies who received NHS before discharge and babies in the neonatal intensive care unit who received hearing screening based on the results of an automatic auditory brainstem response test before discharge . Diagnosis of hearing impairment was defined as well-born babies who failed secondary NHS and were diagnosed with hearing impairment within 3 months after birth, and babies in the neonatal intensive care unit who failed auditory brainstem response screening and were immediately diagnosed with hearing impairment.
To calculate NHS coverage, the number of newborns who received NHS within four weeks after birth was divided by the number of live births. The detection rate of hearing impairment was calculated by combining the rates of primary and secondary screening failure with the rate of newborns who failed secondary screening and were later diagnosed with hearing impairment (Appendix 2). This aggregate approach to calculating the detection rate was necessary because individual-level data on detection were unavailable. This aggregate detection rate does not take into account neonates admitted to the intensive care unit after birth.
Data were analyzed for all 31 provinces in China, which were stratified into three geographic areas based on social and economic development : eastern provinces included Beijing, Tianjin, Liaoning, Shanghai, Jiangsu, Zhejiang, Fujian, Shandong, and Guangdong; central provinces included Hebei, Shanxi, Jilin, Heilongjiang, Anhui, Jiangxi, Henan, Hubei, Hunan, and Hainan; and western provinces included Inner Mongolia, Guangxi, Chongqing, Sichuan, Guizhou, Yunnan, Shaanxi, Gansu, Qinghai, Ningxia, Xinjiang, and Tibet. All data were entered into Epidata 3.0 (The Epidata Association, Odense, Denmark) and analyzed using R version 3.5.1 (R Foundation for Statistical Computing, http://www.r-project.org).
Estimated detection rates of hearing impairment in our study were calculated based on data from the 2018 survey. Rates were calculated for all provinces except Chongqing and Tibet, because data were unavailable on the number of Chongqing newborns diagnosed with hearing impairment among newborns who failed secondary screening, and only 1979 of 50896 live births received NHS in Tibet in 2016. National detection rates were estimated together with 95% confidence intervals (CIs), which were calculated by performing multiple sampling 1000 times based on provincial detection rates.