Pathology/Lab Coding Alert

Question: What is the difference between NEC and NOS in the ICD-9 manual, and will I need to know the difference when ICD-10 goes into effect?

Codify Subscriber

Answer: Yes, ICD-10 will use the terms Not Elsewhere Classifiable (NEC) and Not Otherwise Specified (NOS), just like ICD-9 does.

NEC: Simply put, NEC means you have more specific diagnostic information than the code set represents, so you have to settle for a less-specific code. These codes often have “other” in the definition. For instance, if your lab reports a positive test for low risk human papilloma virus, you should code 795.09 (Other abnormal papanicolaou smear of cervix and cervical HPV), because there isn’t a more specific code available.

NOS: On the other hand, NOS (often listed as ‘unspecified’ in the code definition) means you have to use a less specific code than what’s available because your pathologist didn’t give you enough information to pick a more specific code. For instance, if the pathology report identifies a malignant bone neoplasm but doesn’t specify the site, you’ll have to choose 170.9 (Malignant neoplasm of bone and articular cartilage site unspecified) instead of one of the codes for a specific site.