To the Editor Byars et al1 recently published a large case-control study based on data from Danish health registries. We believe that several important limitations in the study need to be addressed.
In Denmark, all information, including diagnoses, related to hospital visits, is registered in the Danish National Patient Registry (DNPR).2 Information on patient contacts and medicine use in the primary sector (general practice and specialist care) is recorded in the National Health Security Registry (NHSR) and National Prescription Registry (NPS), respectively.2-5
Lüscher M, Thrane JF, Homøe P. Limitations to the Association of Risk of Airway Disease With Removal of Adenoids and Tonsils in Children. JAMA Otolaryngol Head Neck Surg. 2018;144(12):1188. doi:10.1001/jamaoto.2018.2453
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