In medicine, Not Otherwise Specified (NOS) is a subcategory in systems of disease/disorder classification such as ICD-9, ICD-10, or DSM-IV. It is generally used to note the presence of an illness where the symptoms presented were sufficient to make a general diagnosis, but where a specific diagnosis was not made. The DSM-IV, for example, "applies the term not otherwise specified (NOS) to a disorder or disturbance that does not meet the criteria for the specific disorders already discussed".[1] The term was introduced because "it is sometimes impossible for the practitioner completing the diagnostic assessment to categorize all the symptoms that a client is experiencing into one diagnostic category".[2] In the context of mental health diagnoses, four situations have been outlined for which such a diagnosis may be considered appropriate:
- Client meets the general guidelines for a disorder, yet not all of the criteria are met, or the ones present are not considered clinically significant.
- Significant behaviors are noted affecting social and occupational functioning, but are not considered part of the usual presentation for a disorder.
- Uncertainty about etiology or the cause of the disorder exists. This is especially important when it is suspected that the disorder may be related to a general medical condition.
- Insufficient information exists to fully support assigning behaviors to a particular mental disorder in the category, but the general criteria for the category of disorders are evident.[2]
It is noted, however, that the use of an NOS classification invites scrutiny when billing or seeking reimbursement for practitioners.[2]
This classification is commonly used in psychiatric diagnoses, such as in:
It is also used in the conditions:
The ICD-10 also uses this phrase for various things, such as:
The phrase is also used within the List of UN numbers, where it refers to a generic entry, e.g. "UN 1993: Flammable liquid, N.O.S.".