Development and validation of a new grading scale for otitis media.

Background: Grading of acute otitis media (AOM) is important in clinical situations as well as in research. Current grading scales for AOM have used a 6 to 9 point scoring system primarily based on variation of redness and bulging of the tympanic membrane (TM). This study aimed to develop and validate a new scale for grading AOM. Method: The scale was developed in 3 stages based on 32 patients with images taken of the TM when a child attended healthcare centre with othalgia and at follow-up visits. Content validity was used as the method for the first 2 stages. An expert panel reviewed the scale and repeated the process on a revised scale. Reliability was tested with a different expert panel that used the final scale on a sample of TM images in a test-retest and inter-rater and intra-rater agreements were calculated. Results: The scale was developed in 3 steps using expert committees. During the process the description of vascularization was judged to be of insufficient importance for our scale. Inter-rater agreement was moderate (kappa = 0.52) and intra-rater agreement was good (kappa = 0.66 to 0.89) in the test-retest of the final scale. Conclusions: The developed AOM image-based grading scale demonstrates substantial inter- and intra-rater reliability with potential use in clinical research and telemedicine applications. Furthermore, the parameter "redness of TM" is of less importance in our scale as compared with other available grading systems.