Home Health ICD-9/ICD-10 Alert

Published on Tue Apr 20, 2010 PDF

Question: Could you please clarify the difference between the ICD-9 diagnosis code notations "NOS" and "NEC?"

Answer: ICD-9 uses the abbreviations NEC and NOS to denote diagnoses "not elsewhere classified" and "not otherwise specified," respectively.

Although the terms sound similar, they have distinct differences.

Think of NOS as the equivalent of "unspecified" and NEC as "not elsewhere classifiable," meaning youwon't find the term in the ICD-9 book anywhere else.

Tip: Think of NOS as a documentation problem: The physician's documentation does not provide enough information to assign a more specific code.

In black and white: "Codes (usually a code with a 4th digit 9 or 5th digit 0 for diagnosis codes) titled 'unspecified' are for use when the information in the medical record is insufficient to assign a more specific code," according to the ICD-9-CM Official Guidelines for Coding and Reporting.

On the other hand, consider NEC as a shortcoming in the ICD-9 manual: Your doctor provides specific findings, but ICD-9 does not list a specific code that describes them.

By the book: "Index entries with NEC in the line designate 'other' codes in the tabular list," the ICD- 9-CM Official Guidelines for Coding and Reporting notes. "These index entries represent specific disease entities for which there is no specific code."

The ICD-9 system sometimes lumps diagnoses together because the system is outdated and patched. Part of the reason that we have NEC codes is because ICD-9-CM has run out of codes while we wait for ICD-10 to be implemented.