MDC 23: Breaking Down the Coding and Documentation Complexities

By Leigh Poland

May 15, 2024

Medical professionals understand the significance of accurate coding and documentation. One area of coding that facility coders struggle with accuracy are accounts that are coded to Major Diagnostic Categories (MDC) 23. MDC 23 is defined as factors influencing health status and other contacts with health services. This particular MDC is a high-error-prone MDC and has coders faced with many challenges related to coding and documentation.

When it comes to medical coding for signs and symptoms, it is important to define the principal diagnosis (PDX), particularly when a patient is admitted for a symptom or sign or an ill-defined condition. The related code for the definitive diagnosis should be assigned as the PDX. If there is no established diagnosis, only the signs and symptoms that are available at the highest level of certainty should be assigned.

For example, if a patient is admitted with a coma due to poisoning by heroin, the poisoning code would be assigned first based on the Chapter 19 ICD-10-CM guidelines for poisoning, followed by any manifestations that the patient might be experiencing from that poisoning, such as coma. Similarly, if a patient is admitted with syncope and there is a definitive diagnosis of third-degree atrioventricular (AV) block, the AV block should be assigned as the PDX instead of syncope based upon the Chapter 18 ICD-10-CM guidelines for symptoms, signs, and abnormal clinical and laboratory findings.

Mdc 23 Breaking Down The Coding

Common Medical Coding Scenarios

There are certain situations in which a symptom code from chapter 18 of the ICD-10-CM guidelines can be correctly designated as the PDX. These include:

  • Presenting signs or symptoms, and no definitive diagnosis can be made
  • Patient is referred elsewhere for further study or treatment before a diagnosis can be made
  • Symptom is treated in an outpatient setting without additional workup required to arrive at a more definitive diagnosis
  • Provisional diagnosis of a sign or symptom is made and the patient fails to return for further investigation or care
  • Residual late effect is the reason for admissions, and the Alphabetic Index directs the coder to an alternative sequencing
  • A more precise diagnosis cannot be made for any other reason

When it comes to treatment, physical therapy (PT), occupational therapy (OT), and speech therapy (ST) codes group to MS-DRG 945 and 946 when reported as the PDX alongside certain diagnoses, such as altered mental status, malaise, and fatigue, edema, cachexia, and abnormal blood findings. These therapy procedures are used to help patients get back to their normal baseline.

Additionally, code Z48.8 or Z44.9 is used for fitting adjustment of other or an unspecified external prosthetic device. All other aftercare codes should be grouped to DRG 559-561.

As a best practice regarding documenting signs and symptoms related to DRG 948, check whether any etiology for the symptom is documented and linked to each other. If it is, the etiology should be assigned as the PDX.

Common Medical Coding Challenges and Errors

Some of the most common challenges coders face when determining the PDX include:

  • Symptom versus multiple definitive diagnoses to determine what is equally treated and assessed
  • Signs and symptoms versus underlying causes
  • Difficulty in identifying the query opportunity to clarify the etiology of the symptoms
  • Differentiating the therapy procedures as it relates to evaluation versus treatment
  • Signs and symptoms related to chronic or personal history conditions
  • Difficulty in establishing how to code a scenario when the coder queries for the underlying cause of the symptom and the physician responds with "unable to determine"
  • Unclear on Complication and Comorbidity (CC) and Major Complication and Comorbidity (MCC) possibilities
  • Misinterpretation of query responses

Major audit error findings when auditing for MDC 23 include:

  • PDX resequencing to secondary diagnosis (SDX) or vice versa. It is often difficult to determine the definitive diagnosis of the symptom, which results in needing to issue a physician query to clarify the underlying cause of the symptom. Also, sometimes the physician will link the symptom to multiple definitive diagnoses, and it becomes difficult to determine what is the focus of treatment and what meets the definition of PDX.
  • SDX addition, deletion and/or revision are critical to accurate MS-DRG/MDC assignment. Coders should validate all secondary diagnoses and ensure all CC/MCC conditions that are coded meet the definition of reportable diagnosis.
  • Procedure Coding System (PCS) addition and deletion, which is common with PT and OT as it relates to determining treatment or assessment.

Although coding and documentation complexities for MDC 23 can be challenging, medical professionals can ensure effective coding by gaining a proper understanding and knowledge of the official ICD-10-CM coding guidelines and other official coding resources. It is also important to understand high-risk coding errors with this MDC to avoid making the same mistake. Professionals should seek clarification when needed and work closely with physicians and other healthcare professionals to educate them on the nuances of coding for MDC 23 and the common documentation improvement opportunities.

Contact us for more information about supporting your team with our medical coding services, technology, and software related to code updates and guidelines.

Leigh Poland

Leigh Poland RHIA, CCS


Leigh has over 20 years of coding experience and has worked in the coding and education realm over the last 20 years. Her true passion is coding education making sure coders are equipped to do their job accurately and with excellence. Academically, Leigh has graduated from Louisiana Tech University with a Bachelor of Science. Leigh has had the opportunity to present many times in the past at the AHIMA, ACDIS, and AAPC National Conventions. She has been a guest speaker on AHIMA webinars and has written several articles that were published in the AHIMA Journal. Leigh has traveled the US and internationally providing coding education.

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