Impact of different criteria for defining hypopneas in the apnea-hypopnea index

Objectives: To explore the effect of using different scoring criteria for h ypopneas in the scoring of polysomnographic studies: (1) by estimating the level of agreement between apnea-hypopnea index (AHI) scores derived from d ifferent scoring methods, and (2) by examining the effect on the point prev alence of disease using different threshold values of the AHI. Design: Retrospective analysis of 48 diagnostic polysomnographic records. Setting: Tertiary-hospital sleep-disorders clinic. Measurements: AHIs were derived from three different methods for scoring hy popneas. The hypopnea definitions used incorporated different combinations and threshold values of respiratory signal changes in addition to differenc es in the requirement for associated oxygen desaturation or arousal. The le vel of agreement between different scoring methods was assessed by construc ting Bland-Altman plots and calculating intraclass correlation coefficients (ICCs). kappa statistics were used to assess agreement between the differe nt methods using varying thresholds of AHI to categorize sleep apnea (AHI > 5, AHI > 15, and AHI > 20). Results: The random-effects ICC for the three methods was 0.89, suggesting that the different scoring methods tended to rank patients fairly consisten tly. However, the point prevalence of disease estimated by using different thresholds of AHI was found to vary depending on the method used to score s leep studies (kappa, 0.30 to 0.95). Conclusions: These findings have implications for case finding; population- prevalence estimates, and grading of disease severity for access to governm ent-funded continuous positive airway pressure services. Guidelines for sta ndardizing the measurement and reporting of sleep studies in clinical pract ice should be implemented.