Question: What is the difference between 327.23 and 780.57? Tennessee Subscriber Answer: Code 327.23 (Obstructive sleep apnea [adult] [pediatric]) is a definitive diagnosis. Code 780.57 (Unspecified sleep apnea) is located in Chapter 16 of the ICD-9 tabular section and is considered to be a symptom, sign, or ill defined condition. Use 327.23 if the patient has been diagnosed with sleep apnea. Reserve 780.57 for instances in which your neurologist's documentation does not provide any additional specificity than -sleep apnea.- Or, if the condition is transient and no cause can be determined, then 780.57 is again appropriate. A more specific ICD-9 code requires the more specific documentation.