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Table 2 Assessment of risk of bias and representativeness

From: Prevalence of hearing loss and use of hearing aids among children and adolescents in Germany: a systematic review

Studies Risk of Bias Representativeness
Was hearing loss measured in a valid way (validity of data collection [assessment method])? Was hearing loss defined adequately (e.g., in accordance with WHO criteria)? Are data for the full sample available and used for estimation of prevalence? Is the data representative for the general population (children and adolescents) living in Germany?
Studies based on self-reported hearing loss by child or caregiver
 EuroTrak 2017 [15] high RoBa high RoBa low RoB unclear representativenessb
 WaBoLu 1993 [16] high RoBa high RoBa low RoB high representativeness
 Stange 1992 [17] high RoBa high RoBa low RoB lacking representativenessc
Studies reporting hearing loss measured in screening programs
 KiGGS 2009 [18] low RoB low RoB low RoB high representativeness
 RKI 2006 [19] low RoB low RoB low RoB lacking representativenessd
 Kruppa 1995 [20] low RoB low RoB low RoB lacking representativenessc
Studies reporting hearing loss based on data collected in registries
 Destatis 2015 [21] low RoB unclear RoBe low RoB high representativeness
 Neubauer 2011 [22] high RoBf high RoBf unclear RoBg lacking representativenessh
 DZH 2003 [23,24,25] low RoB unclear RoBe unclear RoBg lacking representativenessh
 Streppel 2000 [26,27,28] low RoB low RoB low RoB lacking representativenessd
 CRM 1982 [29, 30] low RoB low RoB low RoB lacking representativenessc
  1. CRM Committee on Medical and Public Health Research; Destatis Federal Statistical Office of Germany; DZH German Registry for Hearing Loss in Children; KiGGS German Health Interview and Examination Survey for Children and Adolescents; Robert-Koch-Institute (German Public Health Institute); RoB Risk of Bias; WaBoLu Institute for Water-, Ground- and Air-Hygiene; PTA Pure Tone Audiometry
  2. aNo objective case ascertainment (subjective self-assessment) resulting in high risk of bias
  3. b Owing to missing information (poor reporting) data representativeness could not be ascertained resulting in unclear representativeness
  4. cNot up-to-date, data collection before 1990 (data refer to the former West Germany) resulting in lacking representativeness
  5. dStudy sample is based on children and adolescents living in a special region (either in the federal state Baden Wuerttemberg [19] or in the city/area of Cologne [26,27,28]) resulting in lacking representativeness
  6. eOwing to missing information (poor reporting), bias due to applying no standardized criteria (i.e., not applying WHO criteria) to define hearing loss cannot be fully excluded resulting in unclear risk of bias
  7. fCase ascertainment was based on international classification of diseases (ICD) coding including a variety of reasons for consulting physicians (i.e., not only hearing loss data were collected in this registry) resulting in high risk of bias
  8. gOwing to missing information (poor reporting), bias due to incomplete data cannot be fully excluded; the studies did not provide the number of the full study sample (source population) resulting in unclear risk of bias
  9. hOnly selected clinicans transferred data to the German registry for hearing loss in children, limiting the representativeness to the entire population living in Germany [23,24,25] and/or data from patients seeking medical advice rather than the general population were collected [22,23,24,25] resulting in lacking representativeness
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