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Abstract
Introduction Current practice at University Hospital Coventry (UHCW) is for qualified, peer reviewed physiologists to manually score multi-channel sleep studies. Apnoea-Hypopnea Index (AHI) or Oxygen Desaturation Index (ODI) used to diagnose sleep disordered breathing and categorise severity. Analysis programs incorporated into device software allows parameters to be scored automatically (AS) without the need for manual scoring (MS) reducing waiting times of analysis reducing time from referral to treatment.
Aim To determine the accuracy and reliability of the AS systems compared with MS and establish if this can be implemented to diagnose sleep disordered breathing.
Methods 121 multi-channel sleep studies (NOX T3) from the department’s Nocturnal diagnostic database (Version 5.1.3, Nox Medical, Reykjavik, Iceland). Each study initially MS were re-analysed using AS. The MS AHI governed the sub-group (Normal = AHI <5, Mild = AHI 5–14, Moderate = AHI 15–29, Severe = AHI >30)1 Agreement measurements used Wilcoxon signed rank test and Spearman’s rank-order correlation.
Results Figure 1 manual scoring produced higher values across all sub-groups for AHI. Spearman’s coefficient showed a strong correlation in all parameters for severe sub-group, scoring of hypopneas showed weakest correlation. Significant differences were seen for moderate and severe AHI, no significant differences seen in normal and mild categories (table 1). 22 studies changed severity when AS performed, 12 changing clinical outcome.
Bland Altman plot showing the agreement of manual vs automated scoring of NOX T3
The median difference (IQR) between the manual and automated scoring system showing correlation and significance
Conclusion AS is reliable scoring severe AHI compared to MS but underscored studies showing false negatives. No clinical differences in the outcomes despite statistical differences seen. AS AHI of 15/hour showed no change to clinical outcomes suggesting MS is not required. Current study shows MS required when AS shows AHI <15/hr as hypopneas are underscored producing false negatives. Larger sample sizes are needed to change clinical practice. Further research using different devices needed.
References
Sleep-related breathing disorders in adults: recommendations for syndrome definition and measurement techniques in clinical research. The Report of an American Academy of Sleep Medicine Task Force. SleepAug 1 1999;22(5):667–689.