What Does NOS Mean in Medical Coding?

Touseef Riaz

August 31, 2022

noc meaning in medical coding

NOS is a common ICD-10 coding system abbreviation. It stands for “Not Otherwise Specified.” This is a common abbreviation used with ICD-10 codes. NOS in medical coding represents/indicates that the patient documentation doesn’t contain enough information. Therefore, only a general diagnosis can be made, but a more specific one can’t. The abbreviation NOS is equivalent to unspecified in medical coding, according to ICD-10 official coding guidelines. 

What is the difference between the NOS code and the NEC code?

NOS and NEC are both common abbreviations used in the ICD-10 coding system. NEC in medical coding stands for “Not Elsewhere Classifiable.” NEC code is used when there is no other specific code available to represent the disease/condition. In ICD-9, these two abbreviations are differentiated; however, ICD-10 classifies both as “Unspecified” or “Other specified.” The use of NEC indicates that the physician made a detailed diagnosis, but the coding system doesn’t get any more specific. 

NOS in Medical Coding

But what does not otherwise specified mean in ICD-10? NOS indicates that the documentation of the patient doesn’t contain/provide enough information to use a specific code/make a specific diagnosis. The ICD-10-CM official guidelines for coding and reporting describe NOS & NEC according to both:

Alphabetic Index

Tabular List

Example for NOS codes in ICD-10-CM:

2022 ICD-10-CM Diagnosis Code C32.1: “Malignant neoplasm of supraglottis.”

C32.1 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes. This edition became effective on October 1st, 2021. ICD-10-CM Diagnosis Code C32.1 is also applicable to the Malignant neoplasm of epiglottis (suprahyoid portion) NOS.

Others include:

  • Malignant neoplasm of aryepiglottic fold or inter-arytenoid fold, laryngeal aspect
  • Malignant neoplasm of extrinsic larynx
  • Malignant neoplasm of false vocal cord
  • Malignant neoplasm of the posterior (laryngeal) surface of epiglottis
  • Malignant neoplasm of ventricular bands
  • Description of C13.1:

2022 ICD-10-CM Diagnosis Code C13.1 “Malignant neoplasm of the aryepiglottic fold, hypopharyngeal aspect.”

C13.1 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes. Short description FOR C13.1 is Malig neoplasm of the aryepiglottic fold, hypopharyngeal aspect. This code is also applicable to:

  • Malignant neoplasm of aryepiglottic fold NOS
  • Malignant neoplasm of inter-arytenoid fold NOS

Other includes:

  • Malignant neoplasm of the aryepiglottic fold, marginal zone
  • Malignant neoplasm of the inter-arytenoid fold, marginal zone

Example for NEC ICD-10 codes:

  1. 2022 ICD-10-CM Diagnosis Code E13 “Other specified diabetes mellitus.”

Description of E13:

E13 should not be used for reimbursement purposes as there are multiple codes below it that contain a greater level of detail.

Includes:

  • Secondary diabetes mellitus NEC
  • Diabetes mellitus due to genetic defects of beta-cell function
  • Diabetes mellitus due to genetic defects in insulin action
  • Postpancreatectomy diabetes mellitus
  • Postprocedural diabetes mellitus

What is an Alphabetic Index in ICD-10?

The ICD-10-CM Coding system is further divided into a tabular list and an alphabetic index. The ICD-10-CM alphabetic index contains the list of terms along with their corresponding codes. This index assists you in determining which code to refer to in the tabular list of ICD-10-CM. The Alphabetic Index consists of the following parts:

  • The Index of Diseases and Injury
  • The Index of External Causes of Injury
  • The Table of Neoplasms
  • The Table of Drugs and Chemicals

What is the Tabular List in ICD-10-CM?

The ICD-10-CM tabular list is a more structured list of codes. The tabular list is divided into chapters, and these chapters are based on the body parts/systems. This list contains categories, sub-categories, and codes. It is essential to use both (an alphabetic index and a tabular list) for locating and assigning an ICD-10 code.

NOS & NEC in ICD-10-CM:

Both the abbreviations are included as the conventions, general coding guidelines, and chapter-specific guidelines of the ICD-10-CM official guidelines. These contain the general rules for using the classification system. Unless otherwise indicated, the conventions, general guidelines, and chapter-specific guidelines are applicable to all healthcare settings. 

According to this, the following is what the abbreviations mean and how they are identified:

Alphabetic Index Abbreviations 

  • NEC “Not elsewhere classifiable.” 

This abbreviation in the Alphabetic Index represents “other specified.” When a specific code is not available for a condition, the Alphabetic Index directs the coder to the “other specified” code in the Tabular List. 

  • NOS “Not otherwise specified.” 

This abbreviation is the equivalent of unspecified.

Tabular List Abbreviations:

NEC “Not elsewhere classifiable.” 

This abbreviation in the Tabular List represents “other specified.” When a specific code is not available for a condition, the Tabular List includes an NEC entry under a code to identify the code as the “other specified” code. 

NOS “Not otherwise specified.”

This abbreviation is the equivalent of unspecified.

Let’s Learn More About Unspecified Codes in ICD-10:

Unspecified codes are the codes in ICD-10 that are used when/if enough information, a specific diagnosis/other specific code isn’t available. This is also specified clearly in the ICD-10-CM official guidelines for coding and reporting. Incomplete documentation is quite a common error, leading to the use of unspecified codes more often. However, you need to be beware of where to use the unspecified codes and where not to use them.

Where to Use Unspecified Codes?

  • In an early evaluation, the physician may not know what specific code to use.
    • For instance, the physician doesn’t have a definitive diagnosis of the patient in the consultation/encounter. Therefore, they cannot make an appropriate/specific diagnosis.  
  • The medical claim can be from a provider not directly involved in the patient’s diagnosis.
  • If the physician doesn’t have or lacks the expertise to use a specific code.

 As mentioned in the official guidelines:

  • There are instances when signs/symptoms or unspecified codes are the best choices for accurately reflecting the healthcare encounter.

Where Not to Use the Unspecified Codes?

There are several instances where unspecified should not be used; these include:

  • If there is sufficient information available to make a specific diagnosis.
  • The diagnosis made includes the basic concepts like:
    • Laterality (bilateral, unilateral, left, & right). According to official guidelines, If the side is not identified in the medical record, assign the code for the unspecified side.
    •  Type
    • Anatomical locations
    • Description of acuity, severity, or other known parameters.
    • Known complications
    • Known comorbidities

The use of unspecified codes is one of the common errors in ICD-10 coding revealed through audits. In medical coding, symptom codes are used quite often. However, when it comes to the definitive diagnosis of the patient, the clinical documentation must support it. In some cases, using unspecified codes is appropriate, especially in cases like emergency care. Medical coding for such cases should be done based on the level of certainty. In case the coders are unclear, physicians should be involved to ensure the highest level of accuracy and compliance.

Appropriate Use of Unspecified Codes – Official Guidelines for ICD-10-CM 2022:

The question here is, what is the acceptable use of unspecified codes?

As mentioned earlier, using unspecified codes is appropriate when there is no sufficient clinical documentation available to support/assign a specific code. Following are the official guidelines for the use of unspecified codes:

  • There are instances when signs/symptoms or unspecified codes are the best choices for accurately reflecting the healthcare encounter.
  • When sufficient clinical information isn’t known or available about a particular health condition to assign a more specific code, it is acceptable to report the appropriate “unspecified” code.
  • Unspecified codes should be reported when they are the codes that most accurately reflect what is known about the patient’s condition at the time of that particular encounter.
  • It would be inappropriate to select a specific code that is not supported by the medical record documentation. 
  • Conducting medically unnecessary diagnostic testing in order to determine a more specific code is also inappropriate.
  • For those categories for which an unspecified code is not provided, the “other specified” code may represent both other and unspecified.

Difference Between Unspecified and Other Specified:

Both unspecified and other specified codes are defined in the ICD-10 official guidelines for coding and reporting.

Unspecified Codes:

Codes titled “unspecified” are for use when the information in the medical record is insufficient to assign a more specific code. 

Example of Unspecified Codes:

2022 ICD-10-CM Diagnosis Code C80.0:

– Disseminated malignant neoplasm, unspecified

– C80.0 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.

2022 ICD-10-CM Diagnosis Code F10.9:

– Alcohol use, unspecified

– F10.9 is non-billable/non-specific ICD-10-CM code. It should not be used for reimbursement purposes as there are multiple codes below it that contain a greater level of detail.

2022 ICD-10-CM Diagnosis Code H54.7:

– Unspecified visual loss

– H54.7 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.

What Does Another Specified Mean in ICD-10?        

Codes titled “other” or “other specified” are for use when the information in the medical record provides detail for which a specific code does not exist.

Example of Other Specified Codes:

2022 ICD-10-CM Diagnosis Code J98.8:

– Other specified respiratory disorders

– J98.8 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.

2022 ICD-10-CM Diagnosis Code T85.6:

– Mechanical complications of other specified internal and external prosthetic devices, implants, and grafts

– T85.6 should not be used for reimbursement purposes as multiple codes below it contains greater detail.

2022 ICD-10-CM Diagnosis Code Z91.89:

– Other specified personal risk factors, not elsewhere classified

– Z91.89 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.

Overuse of Unspecified Codes:

Medical or healthcare encounter requires to be coded at some level of specificity; however, if a specific diagnosis isn’t reached, unspecified codes can be used. In case the physician/provider chooses an unspecified code, even though a more accurate/specific code can be used, it can lead to claim rejections/denials. Following is the list of conditions commonly coded under unspecified ICD-10 codes:

 Alcohol use

Drug use

Neoplasms

Pneumonia

Pressure ulcers

Respiratory failure

Sepsis

Strokes

Other Coding Mistakes/Errors in ICD-10:

  1. Using a code directly from the alphabetic index without locating or assigning the code in the Tabular list.
  2. The inappropriate sequence of the codes
  3. Using a lesser number of codes
  4. Using/reporting too many codes
  5. Not being up-to-date with the changes in official coding guidelines and sticking with the old version.
  6. Using an unspecified or other specified code without exhausting all other possibilities
  7. Considering that ICD-10 codes don’t impact revenues. However, using an outdated/inappropriate code leads to claim denials/rejections. And claim denials impact the practice’s revenues/reimbursements.

Frequently Asked Questions (FAQs)

1. What does NOS mean in medical coding?

NOS is a common ICD-10 coding system abbreviation. It stands for “Not Otherwise Specified.” NOS meaning in medical coding represents/indicates that the patient documentation doesn’t contain enough information. Therefore, a more specific code/diagnosis can’t be made. The abbreviation NOS is equivalent to unspecified in medical coding.

2. What does NOS stand for in medical coding?

NOS stands for “Not Otherwise Specified.” It is one of the common ICD-10 coding system abbreviations.

3. What is NOS disorder?

NOS is commonly used in ICD-10 to indicate that symptoms of a particular illness were sufficient to make a general diagnosis. However, it wasn’t enough for a specific diagnosis. 

4. What is reactive depression NOS?

Not Otherwise Specified (NOS) is a common abbreviation used in coding the Diagnosis of Mental Disorders like depression and anxiety. It indicates that the documentation of the patient doesn’t contain/provide enough information to use a specific code/make a specific diagnosis. 

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