Is it appropriate to affix a new diagnosis code that is discovered after speech therapy sessions have already been attended. For example. 6 months of speech therapy sessions 92507 with a diagnosis code of F80.2 Expressive/receptive language delay was billed and denied. After treatment is rendered an MRI proves lesions in the brain and a new diagnosis of R47.01 Expressive/receptive aphasia which is a covered benefit...I am not sure if we can change the diagnosis because the information was not available to us at the time. HELP!!!