Data extraction and quality assessment
For each included article, we extracted the number of CLP patients treated, patients’ age and sex, type of clefts included, clinical indications to adenoidectomy, type of clinical evaluation (for inclusion and/or outcomes), type of outcome(s) studied, and outcome(s).
Selected studies were assessed for both quality and methodological bias according to the National Heart, Lung, and Blood Institute Study Quality Assessment Tools (NHI-SQAT)[14]. Articles were rated in duplicate by two authors (XX and XX, blinded for review purposes) and disagreements were resolved by consensus. Items were rated as good if they fulfilled at least 80% of the items required by the NHI-SQAT, fair if they fulfilled between 50% and 80% of the items, and poor if they fulfilled less than 50% of the items, respectively.
Also, the level of evidence was scored according to the Oxford Centre for Evidence-based Medicine (OCEBM) level of evidence guide[15].