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InterQual criteria—developed and maintained by Optum—are proprietary, evidence-based clinical decision support guidelines used by hospital case management departments, utilization review (UR) committees, and health insurance payers to evaluate the medical necessity and clinical appropriateness of inpatient admissions, level-of-care placements, surgical procedures, diagnostic imaging, and post-acute transitions. Alongside its primary commercial counterpart (MCG vs. InterQual), InterQual structures clinical utilization assessments around objective patient acuity and therapeutic intervention thresholds while operating subject to federal Medicare coverage rules under 42 CFR § 422.101.
What Is InterQual Criteria and How Is It Developed?
Originally created in 1978 to standardize hospital utilization management under Medicare Conditions of Participation (42 CFR § 482.30), InterQual is an annually updated clinical knowledge base synthesized from systematic reviews of peer-reviewed medical literature, specialty society clinical practice guidelines, FDA labeling, and national CMS coverage policies, vetted by a multidisciplinary panel of independent practicing clinicians.
Rather than relying on subjective narrative impressions, InterQual translates clinical presentations into structured decision trees across three major guideline families:
- InterQual Level of Care (LOC) Criteria: Evaluates the appropriate clinical care setting across the continuum—including Observation, Acute Inpatient (General Medical/Surgical, Telemetry, Intermediate/Step-Down, and Intensive Care / Critical Care), Acute Pediatric, Long-Term Acute Care Hospital (LTACH), Acute Inpatient Rehabilitation (IRF), Subacute / Skilled Nursing Facility (SNF), Home Health, and Outpatient Rehabilitation.
- InterQual Behavioral Health Criteria: Evaluates psychiatric and substance use disorder care placement across inpatient psychiatric admission, residential treatment, partial hospitalization programs (PHP), and intensive outpatient programs (IOP).
- InterQual Care Planning Criteria: Evaluates outpatient and elective prior authorization requests for surgical procedures, advanced diagnostic imaging (MRI, CT, PET, nuclear cardiology), molecular diagnostics and genetic testing, durable medical equipment (DME), and specialty pharmaceuticals.
How InterQual Level of Care Works: Severity of Illness (SI) and Intensity of Service (IS)
At the heart of InterQual’s Acute Adult and Acute Pediatric Level of Care subsets is a dual-requirement clinical decision model that evaluates whether a patient’s documented chart meets both Severity of Illness (SI) and Intensity of Service (IS) thresholds, followed by Discharge Screens for continued-stay reviews:
| InterQual Evaluation Component | Clinical Definition | Representative EHR Data Elements Evaluated | Role in Utilization Review Workflow |
|---|---|---|---|
| 1. Severity of Illness (SI) / Clinical Findings | Objective clinical evidence of acute physiological instability, organ dysfunction, or immediate risk of clinical deterioration | Vital sign thresholds, laboratory values (e.g., serum sodium, troponin, arterial blood gas, creatinine), imaging findings, and acute neurological or hemodynamic signs | Answers why the patient requires hospital-level evaluation rather than routine outpatient management |
| 2. Intensity of Service (IS) / Clinical Interventions | Specific diagnostic, monitoring, or therapeutic interventions that can only be safely and effectively delivered in the requested care setting | Continuous cardiac telemetry, vasoactive IV infusions, frequent IV medication dosing, serial laboratory/neurological checks every 2–4 hours, or ventilator support | Distinguishes Observation status from General Acute Inpatient, Telemetry, Step-Down, or ICU level of care |
| 3. Continued Stay & Discharge Readiness Screens | Day-by-day evaluation of ongoing inpatient need and clinical stability for safe transition to a lower level of care | Resolution of fever/hemodynamic instability, transition from IV to oral medications, ability to tolerate oral intake, and post-acute placement needs | Guides concurrent daily utilization review and discharge planning to SNF, IRF, or home care |
Regulatory Boundaries: InterQual Criteria vs. CMS 42 CFR § 422.101 and the Two-Midnight Rule
A critical compliance distinction in US hospital revenue cycle management and clinical risk operations is that commercial screening guidelines like InterQual do not supersede federal Medicare law:
- Traditional Medicare and the Two-Midnight Rule (42 CFR § 412.3): Under Traditional Medicare (Part A), acute inpatient admission is generally payable when the admitting practitioner documents a reasonable clinical expectation that the beneficiary requires hospital care spanning at least two midnights (or when the procedure is on the CMS Inpatient-Only List or meets the rare/unusual case-by-case exception).
- Medicare Advantage Restrictions on Proprietary Criteria (42 CFR § 422.101(b) and (f)): Under the CMS Contract Year 2024 Medicare Advantage Final Rule (CMS-4201-F), Medicare Advantage (MA) plans are legally required to adhere to the Traditional Medicare Two-Midnight Rule, National Coverage Determinations (NCDs), and Local Coverage Determinations (LCDs). An MA plan cannot use InterQual criteria to deny or downgrade an inpatient admission when Traditional Medicare coverage rules (such as the Two-Midnight benchmark) are satisfied.
- Public Transparency and Licensed Human Review: When coverage criteria are not fully established in Traditional Medicare regulations, 42 CFR § 422.101(f) permits an MA organization to apply internal or licensed commercial criteria only if the clinical evidence base is made publicly accessible. Furthermore, federal CMS guidance and state utilization review laws governing AI and automated claim denials prohibit payers from issuing an adverse medical-necessity determination solely via an automated software screen without individualized review of the patient’s medical record by a qualified, licensed physician or healthcare professional.
EHR Integration and Clinical Informatics Workflows
Modern hospital systems integrate InterQual directly into the electronic health record (such as Epic, Oracle Health, and MEDITECH) through cloud web services, HL7 FHIR APIs, and natural language processing (NLP) modules (such as InterQual AutoReview). When a clinician signs an admission or observation order, the automated service extracts structured FHIR Observation (vital signs and labs), Condition, and MedicationRequest data alongside clinical notes to pre-populate the relevant condition-specific InterQual subset—flagging documentation gaps for the utilization review nurse before the prior authorization or admission notification is transmitted to the payer.
