What is the most reliable sign of acute otitis media?

The most reliable sign of acute otitis media is the loss of tympanic membrane mobility. In acute otitis media, the presence of fluid in the middle ear prevents the tympanic membrane from moving freely in response to pressure changes caused by pneumatic otoscopy. This immobility is a direct indicator of fluid accumulation and infection, making it a critical sign in the diagnosis of the condition.

While bulging of the tympanic membrane, reddening, and air bubbles can all be associated with middle ear issues, they are not as definitive as the loss of mobility. Bulging may indicate significant middle ear pressure, but it can also occur without infection. Reddening can be seen in various ear conditions, such as eustachian tube dysfunction or viral infections, and does not specifically signify acute otitis media. Air bubbles may suggest that there is fluid present but do not confirm the presence of infection, which is the core concern in diagnosing acute otitis media. Thus, observing a lack of mobility is the most reliable and specific sign for determining acute otitis media.