Florida Subscriber
Answer: The difference between "not otherwise specified" (NOS) and "not elsewhere classified" (NEC) is that one reflects your physician's documentation shortcomings while the other reflects your ICD-9-CM's shortcomings, respectively.
You should use an NOS code when your physician fails to document a more specific diagnosis for a patient whose condition requires a five-digit diagnosis code. These codes are highlighted in yellow in the ICD-9-CM expert edition manual published by Ingenix. The NEC codes, on the other hand, are highlighted in gray. Use these codes when there is no diagnosis code in the manual that is as specific as your physician's documented findings.