Coding “Toxic Metabolic Encephalopathy” – An Auditor’s Challenge and A Hospital’s Response

The coding and reporting of the diagnosis “toxic metabolic encephalopathy” (TME) has engendered much discussion over the years. The American Hospital Association “Coding Clinic” has issued advice on the correct coding and reporting of specific types and etiologies of “encephalopathy” beginning with the Fourth Quarter 2009 issue, pages 99-101. As always, we suggest that when questions arise you refer to “Coding Clinic” first and foremost for the most recent and official coding advice applicable to your question. 

In this blog we are focusing on the coding and reporting of the diagnosis “toxic metabolic encephalopathy,” specifically on the instructions, inclusion terms and Excludes 1 note in the Tabular section, codes G92 Toxic Encephalopathy, and G93.41 Metabolic encephalopathy. These codes are in Chapter 6. Diseases of the Nervous System. 

This blog topic was requested by a hospital to explain the coding aspects for reporting G92 Toxic encephalopathy and in particular, the applicable instruction notes in the Tabular section. The hospital’s request was prompted by an audit finding, a discrepancy between the hospital and an external auditor/payer regarding the interpretation and application of an instruction note. The hospital disagreed with the external auditor/payer’s contention that a “T code” for a drug or toxin must always precede code G92 when coding and reporting the diagnosis “toxic metabolic encephalopathy.”

Payer Audit Considerations

Code G92 Toxic Encephalopathy is a Major Complication and Comorbidity (MCC) code. MCC codes have the potential of affecting MS-DRG assignment and reimbursement. When MCCs are reported as a secondary diagnosis code, the facility may receive higher reimbursement from a payer than if the MCC code were not present. For this reason, the presence of an MCC code is often targeted and challenged by payers. This is not to imply that the payer’s challenge is meritless or their sole motivation is to reimburse the hospital less. 

Audit findings and recommendations from any source – payer auditor, internal auditor or other external auditor – should be supported by applicable documentation and application of coding instructions and guidelines, the same way that the hospital’s coding is derived and supported. While no coder is happy when an auditor finds coding errors, keep in mind that the findings and recommendations can be a good learning experience and useful for discussion going forward.  

When challenged by a payer, the facility’s clinical documentation improvement team, attending physician and other clinical staff may provide evidence that the diagnosis, in this case TME, met clinical criteria as supported by pertinent documentation in the patient record. The health information management coding staff may review the same documentation to verify that, in this case code G92 Toxic encephalopathy, was accurately and correctly reported. 

After this facility had responded to the payer’s challenge by stating why the diagnosis TME met clinical criteria and was accurately coded as G92 Toxic Encephalopathy, the payer agreed that the diagnosis TME was valid but still maintained that the TME was incorrectly coded as G92 Toxic Encephalopathy alone, with no “T” code (for a drug or toxin) preceding it.   

Terms defined:

“Encephalopathy” can be broadly defined as a global brain dysfunction (brain damage, brain malfunction or brain disease) manifested by an altered mental state that is not due to an underlying neurodegenerative state. 

The National Institute of Neurological Disorders and Stroke defines “encephalopathy” as follows:

“Encephalopathy is a term for any diffuse disease of the brain that alters brain function or structure. Encephalopathy may be caused by infectious agent (bacteria, virus, or prion), metabolic or mitochondrial dysfunction, brain tumor or increased pressure in the skull, prolonged exposure to toxic elements (including solvents, drugs, radiation, paints, industrial chemicals, and certain metals), chronic progressive trauma, poor nutrition, or lack of oxygen or blood flow to the brain.” 

• “Toxic encephalopathy” is caused by an adverse effect of or exposure to a neurotoxic substance such as a drug or other toxic agent. Toxic encephalopathy is never caused by an infection. 
• “Metabolic encephalopathy” can have many etiologies, commonly including an electrolyte imbalance (dehydration) or infection (urinary tract infection, sepsis). “Septic encephalopathy” is synonymous with “metabolic encephalopathy.” Metabolic encephalopathy is never caused by a drug (codes T36-T50) or toxic agent (codes T51-T65). 

“Toxic metabolic encephalopathy” is a combination of toxic and metabolic factors, a result of infections, the presence of toxins, or organ failure. When the electrolytes, hormones, or other chemicals in the body are off their normal balance, or there is the presence of an infection or toxic chemical, the brain’s function can be affected. The encephalopathy usually resolves when the underlying chemical imbalance is restored or offending infection/toxin removed. https://www.healthline.com/health/hepatic-encephalopathy.

Coding “toxic metabolic encephalopathy” (TME)

Because the term “encephalopathy” is very broad, it is normally preceded in documentation by various terms that describe the reason, cause, or special conditions of the patient that led to the brain malfunction.  

When researching a diagnosis for coding, we always begin with the Index to Diseases and Injuries (Index). Additional, descriptive terms (subterms) for the broad term “encephalopathy” are listed in the Index under the main term Encephalopathy. Since we are focusing on the diagnosis TME and code G92 Toxic Encephalopathy, below are all of the entries listed in which code G92 appears in the Index using the subterms metabolic, metabolic drug induced, metabolic toxic, toxic, and toxic metabolic, as follows: 

Encephalopathy (acute) G93.40

– – drugs – -see also Table of Drugs and Chemicals G92

– metabolic G93.41

– – drug induced G92

– – toxic G92

– toxic G92

– – metabolic G92

From the Index we are directed to code G92 Toxic encephalopathy in the Tabular List of Diseases and Injuries (Tabular). 

• Note: We are using the Index and Tabular as published on the CMS website.  

Here is how code G92 Toxic encephalopathy appears in the CMS Tabular:

G92 Toxic encephalopathy

• Toxic encephalitis
• Toxic metabolic encephalopathy 

Code first, if applicable, drug induced (T36-T50)

• (T51-T65) to identify toxic agent

Check your code book:  CMS publishes the official version of ICD-10-CM and ICD-10-PCS. Hard copy ode books obtained from various publishers should, but do not always, match the CMS Index and Tabular. Sometimes these are simple typos – for example, we saw the word “funderdosinrom” (?) in a guideline. With regard to this blog topic, we noticed a difference between our “code book” with regard to the instruction note “Code First” in G92, printed as follows, with our code book incorrectly adding the instruction terms “code first” (in bold and underlined) preceding “(T51-T65) to identify toxic agent.” Bottom line – if something in your hard copy code book seems odd or incorrect, compare it to the entry on the CMS website.

G92 Toxic encephalopathy – Inclusion term and Instruction

Let’s further examine code G92 Toxic encephalopathy in the Tabular, starting with the inclusion term “toxic metabolic encephalopathy.” This inclusion term is listed beneath the code and code description. Inclusion terms “are the conditions for which that code is to be used.” Ref: “ICD-10-CM Official Guidelines for Coding and Reporting,” Section I.A.10. Therefore, G92 Toxic encephalopathy is the correct code to report for the diagnosis “toxic metabolic encephalopathy” even though the term “metabolic” is not in the description for code G92.

Next, see the instruction “Code first, if applicable,” which applies to codes in both ranges listed – T36-T50 and T51-T65.  Refer to the ICD-10-CM Official Guidelines for Coding and Reporting Section I.A.13. Etiology/manifestation convention (“code first,” “use additional code” and “in diseases classified elsewhere” notes). In other words, is the etiology of the TME a drug or toxic agent? 

The key words in this instruction are “if applicable.” Was the TME drug-induced or caused by a toxic agent? If the documentation is not clear if the TME is drug induced or caused by a toxic agent, we highly recommend a query. 

• If applicable, the query response should specify the drug or toxic agent that caused the TME, in which case a “T” code from T36-T50 or T51-T65 is reported first, followed by G92. 
• If the query response is that the etiology of the TME was not a drug or toxic agent, no “T” code is reported and G92 only is reported for TME.

The counter to the payer/auditor’s contention that a code from T36-T50 or a code from T51-T65 is required and sequenced first, before G92, when coding the diagnosis “toxic metabolic encephalopathy” is dependent on the case and documentation. In our hospital’s case, the provider was queried and documented that the TME was not due to a drug or toxic agent. The hospital responded to the payer auditor accordingly that their original coding was correct. We agree! 

Summary

Both “toxic encephalopathy” (which by definition is caused by a drug or toxin and requires that a “T” code is reported) and “toxic metabolic encephalopathy” (by definition not necessarily caused by a drug or toxin) are both coded to G92.

A code from T36-T50 or a code from T51-T65 is not required and sequenced first, before G92 Toxic encephalopathy unless a drug or toxic agent is applicable to the case and documented as the etiology of the TME. 

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