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Coding Malnutrition and Morbid Obesity on the MDS: Two Core Rules Must Be Followed

The most common mistake that nurse assessment coordinators (NACs) and other MDS assessors make when coding malnutrition, at risk for malnutrition, or morbid obesity on the MDS is being unaware that a dietitian cannot diagnose these conditions, says Carol Maher, RN-BC, RAC-MTA, RAC-MT, RAC-CTA, RAC-CT, CPC, director of education for Hansen, Hunter & Co. PC in Vancouver, WA. “Sometimes, I’m asked several variations of the same ‘Can I code it if?’ question, but the coding guidelines for MDS section I (Active Diagnoses) in the Long-Term Care Facility Resident Assessment Instrument 3.0 User’s Manual don’t allow dietitians to diagnose malnutrition, at risk for malnutrition, or morbid obesity.”

There are multiple reasons why NACs need to ensure that malnutrition, at risk for malnutrition, and morbid obesity are coded accurately in section I, starting with the way that case-mix classification works in the Medicare Part A Patient-Driven Payment Model (PDPM), says Maher. “For the non-therapy ancillary (NTA) component of PDPM, malnutrition or at risk for malnutrition is coded via checkbox at I5600 (Malnutrition (Protein or Calorie) or at Risk for Malnutrition), and morbid obesity is captured as an ICD-10-CM code in item I8000 (Additional Active Diagnoses),” she explains. “Accurately coded, each of these MDS items is worth one point in the NTA comorbidity score calculation.”

In addition, some malnutrition and morbid obesity diagnoses can be captured as an ICD-10 code in I0020B (ICD Code/Resident’s Primary Medical Condition) when they are the primary reason for the Part A stay to generate the default primary diagnosis clinical category for the physical therapy (PT), occupational therapy (OT), and speech-language pathology (SLP) components of PDPM. Therefore, when a resident meets the coding criteria for morbid obesity for both I0020B and I8000, that diagnosis would be “double-coded” in both items. Similarly, if a resident meets the criteria for malnutrition for both I0020B and I5600, malnutrition would be double-coded as an ICD-10 code in I0020B and as a checkmark in I5600.

“However, while at risk for malnutrition can be captured in I5600—it’s in the item name—it cannot be coded in I0020B,” explains Maher. “There is no ICD-10 code to capture a resident being at risk for malnutrition, only for a malnutrition diagnosis itself.”

In a rare instance of the coding instructions (page I-2 in chapter 3) in the RAI User’s Manual instructing assessors to double-code, the primary medical condition diagnosis coded in I0020B also should always be captured in the appropriate item in I0100 – I8000 (Active Diagnoses in the Last Seven Days), says Maher. Note: For more information, see the March 2020 AAPACN article “MDS Item I8000: Solve Common Coding Problems Under PDPM.”

Coding possibilities snapshot

The following chart sums up what may be coded where for malnutrition, at risk for malnutrition, or morbid obesity:

DiagnosisWhere It Can Be Captured in Section I If It Meets Coding CriteriaPotential PDPM Case-Mix Components Impacted
MalnutritionI5600, I0020B*NTA for I5600; PT, OT, SLP for I0020B
At Risk for MalnutritionI5600NTA
Morbid obesityI8000, I0020BNTA for I8000; PT, OT, SLP for I0020B

* Requires appropriate ICD-10 code.

Every fiscal year (FY), the Centers for Medicare & Medicaid Services (CMS) issues an updated PDPM ICD-10 Mappings tool to help providers map ICD-10 codes captured in I0020B and I8000 to primary diagnosis clinical categories and comorbidities, respectively, for the PT, OT, SLP, and/or NTA components of PDPM. The FY 2022 malnutrition and morbid obesity ICD-10 mappings are in effect through Sept. 30, and CMS has proposed no changes for those diagnoses’ mappings for FY 2023 effective Oct. 1, 2022.

Note: See the three charts at the end of this article to review the malnutrition, morbid obesity, and other related ICD-10 diagnosis codes that may or may not be captured in I8000 or I0020B to map into PDPM.

On the quality and care planning side, I5600 qualifies residents for the denominator of the Nursing Home Quality Initiative (NHQI) quality measure (QM), Percent of High-Risk Residents With Pressure Ulcers (Long-Stay)—a measure that feeds into the Long-Stay QM rating in the QM domain of the Five-Star Quality Rating System. In addition, malnutrition, at risk for malnutrition, and morbid obesity obviously play a significant role in care planning. For example, malnutrition can predispose residents to limitations in maintaining normal fluid balance, as well as present complications or increase risk for pressure ulcer/injury, according to the review of indicators for the Dehydration/Fluid Maintenance and Pressure Ulcer/Injury care areas in Appendix C, “Care Area Assessment (CAA) Resources,” in the Long-Term Care Facility Resident Assessment Instrument 3.0 User’s Manual.

Given these significant potential impacts, NACs need to understand the following coding rules:

Section I coding requirement No. 1: A physician-documented diagnosis

“Section I has two primary coding requirements that are identified in the steps for assessment on page I-7 in chapter 3 of the RAI User’s Manual, and they both must be met to code malnutrition, at risk for malnutrition, or morbid obesity,” says Maher. “Assessors can’t lose track of this fact.”

The first requirement is as follows:

Identify diagnoses: The disease conditions in this section require a physician-documented diagnosis (or by a nurse practitioner, physician assistant, or clinical nurse specialist if allowable under state licensure laws) in the last 60 days.  

Medical record sources for physician diagnoses include progress notes, the most recent history and physical, transfer documents, discharge summaries, diagnosis/problem list, and other resources as available. If a diagnosis/problem list is used, only diagnoses confirmed by the physician should be entered.

  • Although open communication regarding diagnostic information between the physician and other members of the interdisciplinary team is important, it is also essential that diagnoses communicated verbally be documented in the medical record by the physician to ensure follow-up.

  • Diagnostic information, including past history obtained from family members and close contacts, must also be documented in the medical record by the physician to ensure validity and follow-up.

“Often, NACs see the dietitian writing about diagnoses of malnutrition, at risk for malnutrition, or morbid obesity in their nutrition assessment,” points out Maher. “Dietitians use these terms when a resident meets the criteria for malnutrition, at risk for malnutrition, or morbid obesity under evidence-based clinical guidelines from the Academy of Nutrition and Dietetics and other professional resources. However, while dietitians can now prescribe a resident’s diet, including a therapeutic diet, under federal regulation when state law allows it, they cannot diagnose.”

Therefore, if a dietitian identifies the likelihood that a resident has malnutrition, is at risk for malnutrition, or is morbidly obese, that should trigger follow-up, says Maher. “When completing an MDS, one of the assessor’s major roles is to keep the resident’s diagnoses up to date. So, if you see an assessment that causes you to question whether there should be an additional diagnosis, the appropriate next step is to query the physician. NACs and other assessors can’t assume that the dietitian’s assessment is enough for a codable diagnosis. The diagnosis must be written by the physician or physician extender.”

But what about BMI?

When coding ICD-10 codes in section I, assessors must follow two sets of coding guidelines: the ones in the RAI User’s Manual and those in the ICD-10-CM Official Guidelines for Coding and Reporting, says Maher. “The FY 2022 guidelines, which were updated effective April 1, are the same as the RAI User’s Manual guidelines in that only the physician or physician extender may diagnose malnutrition and morbid obesity (and even obesity). Again, at risk for malnutrition is not a codable diagnosis, so it’s not addressed in the ICD-10 Official Guidelines, but you still have to follow the RAI User’s Manual guidelines, which require that physician-documented diagnosis.”

The one apparent “discrepancy” between the two sets of guidelines that could impact how these conditions are coded involves BMI, points out Maher. “Five BMI ICD-10 codes (Z68.41 – Z68.45) can qualify a resident for the morbid obesity comorbidity in the NTA component when coded in I8000. Item 14, Documentation by Clinicians Other Than the Patient’s Provider, in the General Coding Guidelines of the ICD-10 Official Guidelines indicates that BMI is one of several limited exceptions ‘when code assignment may be based on medical record documentation from clinicians who are not the patient’s provider.’ The guidelines include the example of a dietitian documenting BMI.”

However, item 14 in the ICD-10 Official Guidelines goes on to state that the associated diagnosis for these limited exceptions must be documented by the physician or physician extender, says Maher. This is reiterated in item C-3, Categories of Z Codes: Status, in chapter 21, “Factors Influencing Health Status and Contact With Health Services (Z00-Z99),” of the guidelines, which states that “BMI [Z68] codes should only be assigned when there is an associated, reportable diagnosis (such as obesity).”

To meet ICD-10 coding guidelines, BMI can only be a secondary diagnosis code, adds Maher. “First, the physician has to diagnose the resident as overweight, obese, or morbidly obese, and then the BMI could be a secondary code that is also captured. But, BMI can’t be a standalone code when documented by the dietitian, according to the ICD-10 Official Guidelines.”

The issue is that morbid obesity is not defined solely by BMI, explains Maher. “Dietitians have parameters that generally state that a BMI of 40 or above is an indicator of morbid obesity. However, some residents who have a BMI over 40 may otherwise be in good health and have a lot of muscle mass, and their physician may say that they are obese but not morbidly obese. With other residents who have a BMI under 40, their physician may say that their weight does put them as morbidly obese due to their general overall health, their age, or certain comorbidities. A set of guidelines can’t make that type of determination, so a physician needs to provide a medical diagnosis of the resident’s condition.”

On top of the guidance in the ICD-10 Official Guidelines, the fact remains that any diagnosis coded in section I, including I8000, also must meet the coding guidelines in the RAI User’s Manual, says Maher. “So, if you want to code a diagnosis in section I, the physician must document it.”

Section I coding requirement No. 2: Active in the last seven days

“The second core coding requirement to capture diagnoses in section I is that they must be active in the last seven days,” points out Maher. Note: The sole exception to this requirement allowed by the RAI User’s Manual is for item I2300 (Urinary Tract Infection (UTI) (LAST 30 DAYS)).

Page I-7 in chapter 3 of the RAI User’s Manual also explains the second requirement:

Determine whether diagnoses are active: Once a diagnosis is identified, it must be determined if the diagnosis is active. Active diagnoses are diagnoses that have a direct relationship to the resident’s current functional, cognitive, or mood or behavior status, medical treatments, nursing monitoring, or risk of death during the seven-day look-back period. Do not include conditions that have been resolved, do not affect the resident’s current status, or do not drive the resident’s plan of care during the seven-day look-back period, as these would be considered inactive diagnoses.
  • Item I2300 UTI, has specific coding criteria and does not use the active seven-day look-back. Please refer to Page I-12 for specific coding instructions for Item I2300 UTI.

  • Check the following information sources in the medical record for the last seven days to identify “active” diagnoses: transfer documents, physician progress notes, recent history and physical, recent discharge summaries, nursing assessments, nursing care plans, medication sheets, doctor’s orders, consults and official diagnostic reports, and other sources as available.

“What this means is: Is the interdisciplinary team actively observing for this diagnosis? Are they actively treating it?” says Maher. “Is the resident on a special diet because of their risk? Is the resident on supplements because they are at risk? The interdisciplinary team needs to be doing something to address that diagnosis—and that should be reflected in the medical record.”

Maher offers the following example:

A new SNF resident had very poor nutrition while living in the community. Perhaps they didn’t have access to food or had trouble feeding themselves, and they are very underweight. Meeting the two primary coding requirements for section I would require the following steps:

  • Even when a resident is obviously underweight according to general clinical standards for body mass index (BMI), the physician would have to be the one to diagnose them as malnourished or at risk for malnutrition before it can be coded in section I, says Maher.
  • Documentation in the medical record must show that the diagnosis is active in the last seven days, says Maher. “For example, the documentation would show the diet that has been ordered and if any other special supplementation is needed, and the care plan specifically would show what the goals are related to the resident’s risk for malnutrition or their malnutrition, as well as the interventions.”

Malnutrition, Morbidly Obesity, and Other Related ICD-10 Codes and How They Map

The following chart reviews malnutrition and malnutrition-related diagnoses and how they impact the PT, OT, and SLP components when captured in I0020B:

Chart 1: Malnutrition-Related Diagnoses and Their Corresponding Default Primary Diagnosis Clinical Category for the PT, OT, and SLP Components of PDPM When Coded in I0020B

ICD-10 CodeCode DescriptionDefault Clinical Category
E43Unspecified severe protein-calorie malnutritionMedical Management
E440Moderate protein-calorie malnutritionMedical Management
E441Mild protein-calorie malnutritionMedical Management
E45Retarded development following protein-calorie malnutritionMedical Management
E46Unspecified protein-calorie malnutritionMedical Management
E500Vitamin A deficiency with conjunctival xerosisMedical Management
E640Sequelae of protein-calorie malnutritionReturn to Provider
E641Sequelae of vitamin A deficiencyReturn to Provider
E642Sequelae of vitamin C deficiencyReturn to Provider
E643Sequelae of ricketsReturn to Provider
E648Sequelae of other nutritional deficienciesReturn to Provider
E649Sequelae of unspecified nutritional deficiencyReturn to Provider
M833Adult osteomalacia due to malnutritionReturn to Provider

The following chart reviews morbid obesity-related, as well as obesity-related, diagnoses and how they impact the PT, OT, and SLP components when captured in I0020B:

Chart 2: Morbid Obesity and Obesity-Related Diagnoses and Their Corresponding Default Primary Diagnosis Clinical Category for the PT, OT, and SLP Components of PDPM When Coded in I0020B

ICD-10 CodeCode DescriptionDefault Clinical Category
E6601Morbid (severe) obesity due to excess caloriesMedical Management
E6609Other obesity due to excess caloriesMedical Management
E661Drug-induced obesityMedical Management
E662Morbid (severe) obesity with alveolar hypoventilationMedical Management
E663OverweightMedical Management
E668Other obesityMedical Management
E669Obesity, unspecifiedMedical Management

The following chart reviews how morbid obesity-related diagnoses impact the NTA component when captured in I8000:

Chart 3: ICD-10 Diagnosis Codes That Count as the Morbid Obesity Comorbidity (1 Point) for the NTA Component When Coded in I8000

Comorbidity DescriptionICD-10 CodeCode Description
Morbid ObesityE6601Morbid (severe) obesity due to excess calories
Morbid ObesityE662Morbid (severe) obesity with alveolar hypoventilation
Morbid ObesityZ6841Body mass index [BMI] 40.0-44.9, adult
Morbid ObesityZ6842Body mass index [BMI] 45.0-49.9, adult
Morbid ObesityZ6843Body mass index [BMI] 50.0-59.9, adult
Morbid ObesityZ6844Body mass index [BMI] 60.0-69.9, adult
Morbid ObesityZ6845Body mass index [BMI] 70 or greater, adult

Source: These charts are excerpted from the FY 2022 PDPM ICD-10 Mappings tool

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