Chest
Volume 120, Issue 3, September 2001, Pages 909-914
Journal home page for Chest

Clinical Investigations
Sleep and Breathing
Impact of Different Criteria for Defining Hypopneas in the Apnea-Hypopnea Index

https://doi.org/10.1378/chest.120.3.909Get rights and content

Abstract

Objectives

To explore the effect of using different scoring criteria for hypopneas in the scoring of polysomnographic studies: (1) by estimating the level of agreement between apnea-hypopnea index (AHI) scores derived from different scoring methods, and (2) by examining the effect on the point prevalence 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 hypopneas. The hypopnea definitions used incorporated different combinations and threshold values of respiratory signal changes in addition to differences in the requirement for associated oxygen desaturation or arousal. The level of agreement between different scoring methods was assessed by constructing Bland-Altman plots and calculating intraclass correlation coefficients (ICCs). κ statistics were used to assess agreement between the different 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 consistently. However, the point prevalence of disease estimated by using different thresholds of AHI was found to vary depending on the method used to score sleep studies (κ, 0.30 to 0.95).

Conclusions

These findings have implications for case finding, population-prevalence estimates, and grading of disease severity for access to government-funded continuous positive airway pressure services. Guidelines for standardizing the measurement and reporting of sleep studies in clinical practice should be implemented.

Section snippets

Materials and Methods

Forty-eight diagnostic sleep study records were retrospectively selected at random from a sleep study database. This database included all sleep studies performed on patients at a tertiary sleep center during a 6-month period. The random-number sequence was computer generated. A large proportion of subjects in the database had AHI scores at the lower end of the spectrum. In order to improve resolution near the threshold of interest, random selection of sleep study records was stratified

Results

There were a total of 48 patient records included in the analysis. Only one patient record was excluded due to poor quality signals, and this was replaced by another randomly selected patient record. Of the patients included in the study, 92% were men (mean age, 52 years; range, 20 to 86 years). The mean body mass index was 32 kg/m2 (range, 24 to 42 kg/m2).

Discussion

This study has compared three different methods of scoring hypopneas that represent the extremes of criteria set in Victoria for analyzing polysomnographic results. Overall, our findings indicate that the method used for scoring hypopneas may influence both the diagnosis of sleep apnea and the rating of disease severity. The limits of agreement presented suggest that AHIs derived from different scoring methods for hypopneas differ to a clinically relevant extent. For example, method A may give

Conclusion

The absolute level of agreement between AHIs derived from some of the different scoring methods used in current clinical practice was poor. However, the different scoring methods tended to rank patients reasonably consistently; for a large proportion of patients, the scoring method may be irrelevant. When different thresholds of AHI used in practice are applied, however, the inconsistency in classification becomes more apparent. These findings have implications for case finding, population

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The study was funded by the Victorian Department of Human Services.

This study was performed at the Austin and Repatriation Medical Center, Heidelberg, Victoria, Australia.

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