RESUMEN
INTRODUCTION: Healthcare databases are a valuable source for epidemiological research in obstructive sleep apnoea, but accurately registered diagnoses are pivotal in contributing quality evidence. We examined positive predictive values (PPV) of the International Classification of Diseases, tenth version (ICD-10) diagnosis for "obstructive sleep apnoea" and "sleep apnoea" in the Danish National Patient Register. METHODS: Using the Danish National Patient Registry, we randomly sampled 100 patients from the North Denmark Region diagnosed with "obstructive sleep apnoea" (ICD-10 code DG4732) and 100 patients diagnosed with "sleep apnoea" (DG473*) during the year 2020. We calculated the PPV using a documented Apnea-Hypopnea Index (AHI) ≥ 5 to confirm the recorded diagnosis. A total of 70 patients were referred to the private sector for assessment of the AHI and excluded due to limited access to their data. RESULTS: The study population included 130 patients, among whom 64 were diagnosed with "obstructive sleep apnoea", and 66 patients were registered with "sleep apnoea". The PPV for "obstructive sleep apnoea" was 93.8% (95% confidence interval (CI): 85.0-97.5%), and the PPV for "sleep apnoea" was 80.3% (95% CI: 69.2-88.1%). CONCLUSIONS: Our findings indicated a high validity of the ICD-10 code DG4732 with a PPV of 93.8% and a lower PPV (80.3%) for the ICD-10 code DG473* for identifying patients with obstructive sleep. The "obstructive sleep apnoea" diagnosis is a suitable source of data for epidemiological research to identify patients with the disease. FUNDING: None. TRIAL REGISTRATION: Not relevant.