3.1 CC versus MCC Recognition and CC Exclusion Lists
Key Takeaways
- CMS classifies secondary diagnoses as a major complication or comorbidity (MCC), a complication or comorbidity (CC), or neither; only MCC and CC can move many MS-DRG families to a higher-paying severity tier.
- Many medical MS-DRG families split three ways—with MCC, with CC, and without CC/MCC—and the grouper uses the single highest qualifying secondary diagnosis, not a count of CCs.
- A code that is generally a CC or MCC can be treated as a non-CC for grouping when it is closely related to that encounter’s principal diagnosis on the CC Exclusions List (IPPS Table 6K / MS-DRG Definitions Manual Appendix C).
- Exclusion-list logic does not delete the diagnosis from the claim; it prevents that secondary diagnosis from acting as severity for MS-DRG assignment on that pairing.
- Do not invent unofficial CC/MCC code lists or unpublished pairings; use the current fiscal-year CMS tables and the Definitions Manual, then confirm the condition still meets UHDDS secondary-diagnosis criteria.
3.1 CC versus MCC Recognition and CC Exclusion Lists
Quick Answer: CMS labels secondary diagnoses as MCC, CC, or neither. Many Medicare Severity Diagnosis Related Group (MS-DRG) families then pay in three tiers. A diagnosis that is generally a CC or MCC can still be treated as a non-CC for grouping when the CC Exclusions List (IPPS Table 6K, also Appendix C of the ICD-10 MS-DRG Definitions Manual) finds it closely related to that stay’s principal diagnosis.
The Inpatient Prospective Payment System (IPPS) pays one MS-DRG per acute inpatient stay. That MS-DRG carries a relative weight—a CMS figure that represents expected resource use compared with the average Medicare case. Secondary diagnoses matter because some of them tell the grouper that this stay should consume more resources than the base family. Clinical documentation integrity (CDI) work in Domain I is not “finding extra words.” It is recognizing which documented conditions can lawfully change severity, which cannot, and which look like severity until exclusion-list logic turns them off.
This chapter does not treat Hospital-Acquired Condition (HAC) claim-level payment rules or the separate HAC Reduction Program as part of CC/MCC recognition. Those are later topics. A HAC code can still appear on a CC or MCC list; that overlap is not the same as saying “HAC” and “MCC” are one program.
The three severity labels
CMS publishes, with each IPPS fiscal-year update:
| CMS table (IPPS files) | What it is | What CDI does with it |
|---|---|---|
| Table 6I | Complete MCC list (plus add/delete files in the same table family) | Identifies secondaries that can move a three-tier family to the with MCC MS-DRG |
| Table 6J | Complete CC list (plus add/delete files) | Identifies secondaries that can move the family to with CC when no eligible MCC remains |
| Table 6K | Complete CC Exclusions List | Identifies principal-diagnosis pairings that stop a listed CC/MCC from acting as severity |
Major complication or comorbidity (MCC) is CMS’s high-resource secondary-diagnosis class. Complication or comorbidity (CC) is the moderate-resource class. Neither means the diagnosis is not on the current MCC or CC list. “Neither” is not a coding insult. Chronic, stable conditions are often reportable when they meet Uniform Hospital Discharge Data Set (UHDDS) secondary-diagnosis criteria—clinical evaluation, therapeutic treatment, diagnostic procedures, extended length of stay, or increased nursing care and monitoring—yet they will not, by themselves, advance a three-tier family.
Lists change when CMS publishes the IPPS final-rule tables. A pocket card from a prior fiscal year is a study aid, not the current source. This independent resource does not reprint code tables. If you need the current designation, open the CMS file for the discharge’s fiscal year.
Three-tier MS-DRG families
Many medical families split into three MS-DRGs that share a base clinical concept:
- With MCC — at least one secondary diagnosis remains an MCC after exclusion-list (and other grouper) logic.
- With CC — no eligible MCC remains, but at least one eligible CC remains.
- Without CC/MCC — no eligible CC or MCC remains.
The grouper does not add CCs together to invent an MCC. Two eligible CCs still group to the with CC tier. An eligible MCC outranks any number of CCs. Some families are only two-tier (for example, with MCC versus without MCC, or with CC/MCC versus without). Some MS-DRGs do not split on CC/MCC at all. CDI language should name the family pattern in front of you, not assume every chart has three rungs.
Worked encounter: three labels, one family
A 71-year-old is admitted from the emergency department for increased dyspnea and wheezing. After study, the condition that occasioned admission is an acute exacerbation of chronic obstructive pulmonary disease (COPD). The record also contains three secondary statements:
- Acute hypoxemic respiratory failure treated with a defined oxygen target and close monitoring — if this diagnosis is an MCC on the current Table 6I and is not excluded for this principal diagnosis, the family moves to with MCC.
- Hyponatremia treated with a measured fluid plan — if this diagnosis is a CC on Table 6J and is not excluded, it supports with CC only when no eligible MCC remains.
- Essential hypertension, unchanged from the home regimen, mentioned in the history — if it is neither CC nor MCC, it may still be reported if it was evaluated, but it does not climb the family.
If the only “severity” on the chart is hypertension, the working DRG is the without-CC/MCC member of that family. Adding a second neither-diagnosis does not create a CC.
What the CC Exclusions List actually does
CMS states the purpose in the MS-DRG definitions material: depending on the principal diagnosis, some diagnoses that are CCs or MCCs when reported as secondaries may be excluded if they are closely related to the principal diagnosis. The operational files CDI teams use are:
- Table 6K — complete CC Exclusions List for the fiscal year.
- Tables 6G.1 / 6G.2 — additions to the exclusion list (secondary-diagnosis order and principal-diagnosis order).
- Tables 6H.1 / 6H.2 — deletions from the exclusion list.
- Appendix C of the ICD-10 MS-DRG Definitions Manual — the same concept in grouper-manual form.
Appendix C is organized in three parts. Part 1 lists diagnoses that are CC or MCC as secondaries and points to the principal-diagnosis collections that convert that secondary to a non-CC for grouping. Part 2 covers a smaller set of diagnoses that are MCC only when the patient is discharged alive; otherwise they group as non-CC. Part 3 describes suppression logic for selected MS-DRGs: a secondary that already sits inside that MS-DRG’s definition is not also used as CC/MCC severity for that assignment.
Exclusion is a pairing rule, not a personality trait of the code. The same secondary diagnosis may act as a CC with one principal diagnosis and act as a non-CC with another. The diagnosis can remain on the claim when it was evaluated or treated. What disappears is its ability to move the three-tier family on this encounter.
Conceptual pairing (no invented codes)
Imagine a principal diagnosis of acute decompensated systolic heart failure. A secondary statement that merely restates volume overload inherent to that decompensation may be a CC or MCC in other pairings, yet Table 6K / Appendix C can treat that closely related secondary as a non-CC here. Querying the attending to “please add a severity diagnosis” that only renames the principal condition does not create a new resource story. It creates a chart that looks busy and groups as if the extra line were never a CC.
Contrast that with an unrelated, treated acute kidney injury that is a CC or MCC on the current list and is not excluded for that heart-failure principal diagnosis. That second condition can change the tier because it is not the same clinical event as the principal diagnosis.
How CDI uses the lists without turning them into a code scavenger hunt
- Identify the principal diagnosis candidate using the UHDDS “after study, occasioned the admission” test (section 3.3 and later Domain VI sections develop this fully).
- Inventory secondary conditions that were evaluated or treated, not problem-list fossils.
- Classify each secondary as MCC, CC, or neither using the current-year CMS lists—not memory from a prior job.
- Run the pairing mentally (or in the encoder) against Table 6K / Appendix C before you tell a physician the working DRG “needs an MCC.”
- Query only when a clinically supported condition is missing, conflicting, or unspecified—not to manufacture a tier after exclusion logic has already answered the question.
The encoder is not optional decoration. If two experienced reviewers disagree about whether a secondary “should count,” the current Definitions Manual and Table 6K settle the grouping question. CDI still settles the clinical question: is this condition present, linked, and documented by a provider?
Traps that invert this section on exam items
- Treating every chronic disease as a CC because “the patient is complex.” Complexity in the room is not the same as CMS severity class.
- Assuming two CCs equal an MCC in a three-tier family.
- Confusing “the diagnosis is reportable” with “the diagnosis changes the MS-DRG.”
- Using a nurse-only or dietitian-only label as if it created an MCC without required provider documentation (query rules belong in Domain III; the grouping point still stands).
- Memorizing an unofficial code list and ignoring the fiscal-year table that actually shipped with the grouper.
- Mixing this logic with HAC payment stripping or with the HAC Reduction Program’s hospital-wide 1% cut—those rules use different statutes and different later chapters.
Severity recognition is therefore a three-gate test: Is it MCC, CC, or neither? Does an exclusion or suppression rule neutralize it for this principal diagnosis? Does the record still support reporting it at all? Missing any gate produces a working DRG that will not survive coding reconciliation or contractor review.
A secondary diagnosis appears on the current CMS complete CC list (IPPS Table 6J). For this stay, the same diagnosis also appears on the CC Exclusions List (Table 6K) paired with the principal diagnosis. For MS-DRG grouping, that secondary diagnosis:
In a three-tier MS-DRG family (with MCC / with CC / without CC/MCC), the patient has two secondary diagnoses that remain eligible CCs after exclusion-list logic and has no eligible MCC. The case groups to:
A provider documents essential hypertension, stable on the home amlodipine dose, as a secondary condition. The diagnosis is not on the current CMS MCC list or CC list. The CDI specialist should treat this as: