10.2 Medical Necessity Criteria: InterQual and MCG
Key Takeaways
- InterQual and MCG are widely used commercial clinical decision-support / medical necessity criteria tools—not substitutes for Medicare statute, regulation, National Coverage Determinations (NCDs), Local Coverage Determinations (LCDs), or the Two-Midnight payment framework
- Hospitals and payers use these tools for consistent screening of admission status, level of care, and continued stay; a criteria ‘mismatch’ is a prompt for physician review and better documentation, not an automatic denial or automatic inpatient order
- Medicare coverage turns on whether services are reasonable and necessary under Medicare rules and supported in the record; proprietary criteria may help organize clinical factors but cannot override CMS coverage policy
- Medicare Advantage plans must follow Medicare coverage criteria and may not use internal or proprietary standards that are more restrictive than Traditional Medicare; tools can support review workflows if applied consistent with those CMS requirements
- Case managers apply criteria transparently, escalate secondary physician review when indicated, and ensure the chart tells the clinical story that criteria screens are meant to summarize
10.2 Medical Necessity Criteria: InterQual and MCG
Quick Answer: InterQual and MCG (Milliman Care Guidelines) are commercial criteria sets used to screen medical necessity and level of care. They improve consistency in utilization management, but they are not Medicare coverage policy. For Medicare beneficiaries, status and coverage decisions must align with CMS rules (including the Two-Midnight framework for inpatient hospital care), NCDs/LCDs when applicable, and documentation of reasonableness and necessity in the medical record.
Utilization management (UM) in hospitals depends on shared language for “Does this patient need hospital care, and at what status/level?” Proprietary criteria products—most commonly referenced on the ACM exam as InterQual and MCG—are the tools many organizations use to answer that question consistently across reviewers, shifts, and payers.
What These Tools Are (and Are Not)
Commercial criteria as decision support
InterQual and MCG provide structured, evidence-informed criteria for scenarios such as:
- Acute inpatient vs observation/outpatient hospital care
- Continued-stay (concurrent) review
- Select post-acute or procedure-related level-of-care screens (depending on modules licensed by the organization)
They typically organize clinical indicators—vital-sign instability, oxygen needs, risk scores, failed outpatient management, procedure complexity, and similar factors—into algorithms or point-based screens that a trained reviewer applies to the chart.
What they are not
| Misconception | Reality |
|---|---|
| “InterQual/MCG = Medicare coverage” | Medicare coverage is governed by the Social Security Act, CMS regulations and manuals, NCDs/LCDs, and claim-processing rules (including Two-Midnight inpatient payment policy) |
| “Criteria met = automatic payment” | Payment still depends on correct billing, eligibility, authorization rules, and medical-record support |
| “Criteria not met = automatic denial forever” | A screen can be incomplete, outdated relative to new findings, or missing documented comorbidities; physician secondary review and updated documentation often change the picture |
| “Case manager can override the attending with a criteria printout” | Final clinical admission/status decisions rest with qualified practitioners; non-physicians do not make the final determination that inpatient care is not warranted under hospital CoP/UR rules |
Think of commercial criteria as a shared checklist and escalation language, not a coverage statute.
Medicare Coverage vs Commercial Screens
For Traditional Medicare hospital inpatient/outpatient status questions, the case manager should keep two layers distinct:
- Medicare coverage / payment layer — Is the service covered and payable under Part A or Part B based on CMS rules? For inpatient hospital admissions, the Two-Midnight benchmark/presumption framework and related exceptions apply. Coverage may also be limited or shaped by NCDs/LCDs for specific services.
- Operational UM layer — How does the hospital consistently identify cases needing physician clarification, UR committee review, or concurrent management?
A stay can “meet InterQual inpatient” and still fail Medicare payment expectations if the record does not support medical necessity or the admission decision under CMS rules. Conversely, complex patients may require inpatient care under CMS case-by-case short-stay principles even when a simplistic screen looks borderline—if the practitioner’s judgment and complex medical factors are clearly documented.
Medicare Advantage nuance
CMS has emphasized that Medicare Advantage (MA) organizations must ensure enrollees have access to medically necessary care consistent with Traditional Medicare coverage criteria. MA plans may use prior authorization and concurrent review, and they may use decision-support tools, but they may not apply internal or proprietary criteria that are more restrictive than Traditional Medicare coverage rules. For inpatient hospital care, MA medical necessity reviews must align with Medicare inpatient admission criteria (including 42 C.F.R. § 412.3 concepts). ACM candidates should treat “the plan’s InterQual says observation” as a communication and documentation problem to resolve against Medicare-aligned clinical factors, not as an automatic clinical truth.
How Case Managers Apply Criteria Day to Day
Primary review
- Identify payer and product (Traditional Medicare, MA, Medicaid, commercial).
- Gather clinical facts from ED notes, H&P, orders, vitals, diagnostics, and response to treatment.
- Apply the hospital’s licensed criteria set for the relevant guideline.
- Document the review outcome in the UM/CM system per policy (criteria version, indicators met/not met, reviewer).
When criteria are not met or are equivocal
Best practice is escalation, not silent disagreement:
- Discuss with the attending/ED physician: What is the expected hospital course? What risks make outpatient management unsafe?
- Ask for specific documentation (severity, failed lower level of care, monitoring needs, procedure plan).
- Involve physician advisors / secondary physician reviewers when available.
- Route to UR committee processes when hospital policy and Conditions of Participation require committee action (especially for status changes—see §10.4).
Concurrent review
Criteria are reapplied as the clinical picture changes. Improvement may support transition from inpatient to discharge or to a lower level of care; deterioration may support continued stay or a status upgrade from observation to inpatient via a new practitioner order grounded in medical necessity—not via criteria software alone.
Documentation That Makes Criteria Useful
Criteria tools fail when the chart is thin. High-yield documentation themes include:
- Why hospital care is needed now (not why the patient is socially complex alone—though SDOH may affect safe discharge planning)
- Expected trajectory (hours vs midnights; anticipated diagnostics/therapeutics)
- Risk if managed outside the hospital (arrhythmia risk, hypoxia, bleeding, sepsis trajectory, post-procedure monitoring)
- Response to treatment over time (supports continued stay or readiness for transition)
- Comorbidities and frailty that modify risk even when the chief complaint seems “simple”
Case managers add value by translating criteria language into clinician-friendly prompts: “The reviewer needs the oxygen requirement and mental-status changes in the note,” not “InterQual denied you.”
Ethics and Professional Boundaries
ACMA-aligned practice expects honesty with patients and teams about uncertainty and payer processes. Criteria should never be used to coerce unsafe discharge, hide observation implications, or invent clinical findings to “make criteria.” If criteria and clinical judgment diverge, the path is transparent escalation and accurate documentation—not chart gamesmanship.
Linking Forward
Criteria screens feed authorization workflows, denial prevention, peer-to-peer discussions (§10.3), and Condition Code 44 analyses when an inpatient order appears unsupported on internal review (§10.4). Master the hierarchy: patient safety and practitioner judgment first, CMS coverage rules for Medicare payment, commercial criteria as structured support.
Which statement best describes InterQual or MCG criteria in Medicare hospital status decisions?
A Medicare Advantage plan reviewer cites a proprietary observation guideline that appears stricter than Traditional Medicare inpatient admission criteria. What is the most accurate case-management framing?
During primary UM review, a patient’s chart does not meet the hospital’s inpatient criteria screen, but the attending believes inpatient care is required because of complex comorbidities and risk. What is the most appropriate next step?