Sadé and Tos classifications of the tympanic membrane: not reliable?

Authors


Abstract

Objectives. Retraction pockets of the tympanic membrane may progress to cholesteatoma.1 To assess and describe the condition of retraction pockets and to monitor their progress, classification systems are used; this classification is of particular importance when follow-up is conducted by more than one clinician. The Sadé classification is used for the pars tensa and the Tos classification system for the pars flaccida. Although widely used, neither method has been validated or evaluated for reliability when applied by different users.

Method. A series of 20 standardised slides of retraction pockets (10 each of PT and PF retractions) was shown to 22 Otolaryngologists. Participants were asked to classify each lesion using the appropriate classification according to supplied, printed definitions.

Results. Overall inter-rater reliability was very low (mean kappa of 0.39), with very high levels of variability. Levels of agreement between raters was lower when classifying PF retractions than PT retractions (= 0.01). No slide was classified unanimously as a single grade. Some slides even had an equal distribution of classifications spread between all grades of the classification system. No significant difference in inter-rater reliability was found between grades (P = 0.7).

Conclusions. This is the first attempt at validation of the Tos and Sadé classification systems for retraction pockets. Despite the reliance on classification of retraction pockets, it would appear from this study that the value of these classification systems may be limited. Clinical decisions based on classifications may be flawed, particularly when made on the basis of a classification made by another clinician.

Reference

1 Akyildiz N., Akbay C., Ozgirgin O.N., et al. (1993) The role of retraction pockets in cholesteatoma development: an ultrastructural study. Ear Nose Throat J.72, 210--212

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