Degree: Master of Science Abstract: Background: There is little epidemiological data on oropharyngeal dysphagia or swallowing dysfunction (SwD) in otherwise healthy infants and toddlers (OHIT). However, there is enough information to confirm that it is far from rare and that it constitutes a significant proportion of observational and surgical case series reporting hospital admissions with recurrent lower respiratory infections and interventions augmenting laryngeal closure and protection. Given the inherent drawbacks of standard instrumental diagnostic tests of SwD, that prohibits wider and frequent use and utility as screening tools, a consideration for resorting to a parent reported outcome tool seems a reasonable objective. Objectives: 1. To identify and appraise the available instruments or questionnaires used to evaluate SwD in the OHIT cohort (chapter 2). 2. To establish a PRO-based assessment questionnaire for SwD in OHIT and validate its content from the perspective of parents and clinicians (chapter 3). Methods: 1. Systematic review (chapter 2): • Data Sources. A Librarian searched Prospero, Cochrane Library, Embase, Medline, PsycINFO, HaPI, CINAHL and SCOPUS using the MeSH term for “deglutition” and “screening methods” from the inception to August 2018. The search was limited to age from 0-18 years old only and English language. • Study Selection. All studies that included a questionnaire assessing SwD in children were eligible. Two independent reviewers evaluated the result and included only those designed as parent reported outcome tools. We excluded instruments designed for specific conditions or eating and feeding difficulties. • Data Extraction. The information extracted from the included article were the authors, publication year, the name of the questionnaire, studied population, study design, scale type, whether the construction was based on PRO or results that were compared with standard assessment instrument, and reported psychometric assessment. The COSMIN tool was used for assessment. 2. Mixed-method study method (chapter 3): • Design: An exploratory mixed-method study. • Setting: Pediatric Aerodigestive and Aspiration clinic in a tertiary care center. • Main outcome: Content validity ratio (CVR) and index (CVI). We recruited parents of OHIT with SwD and excluded those with a confounding diagnosis (syndromes or neurological impairments). In-person interviews were conducted and thematically analyzed to extract the relevant domains and items. A similar analytic method was performed on the related reports generated from a systematic review and literature search. Four-member checking groups of parents and experts were conducted to maintain rigour. A panel of experts assessed and established items’ content validity using Lawshe’s content validity ratio and index through the application of a modified Delphi technique. An item achieved validity if it passed a CVR of 0.622. A priori CVI threshold was selected to be 80%. Results: 1. Systematic review results (chapter 2): Of the 3488 screened articles, the pediatric version of the Eating Assessment Tool (PEDI-EAT-10) was identified. It was adapted from the adult EAT-10. The authors assessed its validity and reliability using a cohort of children with cerebral palsy. Upon evaluation, major concerns with the process of development and validity of internal structure were identified. 2. Mixed-method study results (chapter 3): We achieved information saturation after interviewing ten parents and generated seven domains with 72 items. Three domains were extracted from the literature, which had also emerged from the parental interviews. Over three rounds of modified Delphi content validation, the domains were reduced to three (swallowing, breathing, and illness) containing 21 items, which passed the CVR threshold of 0.622, and achieved a CVI of 82.1%. Conclusions: We constructed and validated the content of a new PRO instrument to assess SwD in OHIT. It is composed of three primary domains representing 21 items. This tool bridges the gap identified in the literature through a systematic review. It has the potential to screen for SwD and assess management outcomes specifically for this population, after establishing its construct validity.