Denial Reason Registry

Overview

• 47 denial reason codes across 3 primary categories
• 3 secondary categories (Benefit Limit has 3 sub-types; Clinical Justification has 2; Administrative has 2)
• Overturn rate range: 34% (FUNCTIONAL_CAPACITY) to 73% (AUTH_REQUIRED)
• Average overturn rate: ~55% across all codes
• Highest-confidence appeals: AUTH_REQUIRED, CRITERIA_MISMATCH, INELIGIBLE_MEMBER (procedural origins)
• Lowest-confidence appeals: FUNCTIONAL_CAPACITY, CLINICAL_THRESHOLD, EVIDENCE_INSUFFICIENT (clinical judgment required)

Core Concepts

Data Structure

Each denial reason entry contains:

{
  "code": "FREQ_LIMIT",
  "description": "Service frequency exceeds plan limits",
  "category": "Benefit Limit",
  "sub_category": "Frequency",
  "appeal_overturn_rate": 0.42,
  "sample_size": 847,
  "confidence_interval": [0.39, 0.45],
  "payer_variance": 0.08,
  "seasonal_q1_variance": -0.03,
  "seasonal_q2_variance": 0.02,
  "seasonal_q3_variance": 0.01,
  "seasonal_q4_variance": 0.00,
  "notes": "Frequency limits easily challenged with objective clinical evidence (visit history + medical necessity). Higher overturn at Medicaid (48%), lower at Medicare Advantage (37%)."
}

Field meanings:
• code — Unique identifier (immutable, used in precedent objects)
• description — Human-readable denial reason
• category — Primary grouping (Benefit Limit, Clinical Justification, Administrative)
• sub_category — Secondary grouping for drill-down analysis
• appeal_overturn_rate — Historical approval rate (0.0–1.0)
• sample_size — Number of appeals analyzed (higher = more reliable)
• confidence_interval — 95% CI around overturn_rate (indicates statistical reliability)
• payer_variance — Standard deviation of overturn_rate across payers (high variance = payer-dependent appeal outcomes)
• seasonal_q_variance — Deviation from annual average in Q1–Q4 (Q4 typically sees +2–3% administrative errors)
• notes — Context, common appeal arguments, payer-specific patterns

Categories & Codes

Benefit Limit (13 codes)

Denials based on plan-defined caps: frequency limits (max visits/month), duration limits (max episode length), and visit limits (max per episode). These codes overturn at 42–48% historically because they respond well to objective clinical evidence. #### Frequency #### Duration #### Visits

Clinical Justification (18 codes)

Denials based on clinical standards and evidence: medical necessity, functional capacity, and clinical thresholds. These codes overturn at 34–58% and require strong clinical documentation. Medical necessity denials are most defensible (58%); functional capacity denials are hardest to appeal (34%). #### Medical Necessity #### Functional Capacity & Standards #### Clinical Thresholds

Administrative (16 codes)

Denials based on procedural requirements: prior authorization, member eligibility, and claims processing. These codes overturn at highest rates (68–73%) because many represent process failures unrelated to clinical merit. #### Prior Authorization & Auth-Adjacent #### Member Eligibility #### Administrative Processing

Overturn Rate Patterns

By Category

High-Confidence Appeals (>60% overturn)

• AUTH_REQUIRED (73%) — Payer did not process auth or lost request
• INELIGIBLE_MEMBER (72%) — Eligibility records out of sync
• AUTH_EXPIRED (71%) — Timing issue; request valid but expired
• CRITERIA_MISMATCH (69%) — Payer's criteria vague or overly restrictive
• AUTH_INCOMPLETE (68%) — Resubmit with complete documentation
• VISIT_AUTH (68%) — Auth was issued; appeal cites authorization letter
Appeal strategy: Focus on procedural fix (resubmit auth, verify eligibility). Minimal clinical evidence needed.

Medium-Confidence Appeals (50–59% overturn)

• MED_NECESSITY (58%) — Strong clinical documentation
• INELIGIBLE_SERVICE (58%) — Requires plan change (low appeal value)
• EOB_MISMATCH (56%) — Requires EOB clarification
• MED_NECESSITY_DECLINE (55%) — Requires baseline + decline metrics
• FREQ_SEASONAL (51%) — Seasonal variation justifies higher intensity
• TREATMENT_STANDARD (51%) — Evidence-based guideline challenge
• EVIDENCE_INSUFFICIENT (50%) — Submit missing clinical documentation
Appeal strategy: Gather missing clinical evidence. Strong documentation = higher success.

Low-Confidence Appeals (<45% overturn)

• FUNCTIONAL_CAPACITY (34%) — Hardest to challenge; requires independent evaluation
• DUR_LIMIT (39%) — Plan-defined boundary; rarely overturned
• VISIT_OVERRIDE (40%) — Plan approved visits for different diagnosis
• FUNCTIONALITY_THRESHOLD (37%) — Payer's functional standard differs from clinician's
• FREQ_LIMIT (42%) — Benefit limit; moderate appeal candidate
Appeal strategy: Strong clinical narrative + objective metrics (ROM, pain scale, ADL function). Independent eval if available.

Seasonal Variations

Overturn rates shift by quarter, reflecting payer staffing, guideline updates, and claim volume patterns: Implication: Appeal timing matters. File AUTH_REQUIRED denials in Q4 when payer errors are highest.

Query Examples

All denial reason queries are free (reference data, no precedent access). Queries do not consume marketplace credits.

List All Denial Codes

GET /api/registries/denial-reasons

Response:

{
  "denial_reasons": [
    {
      "code": "FREQ_LIMIT",
      "description": "Service frequency exceeds plan limits",
      "category": "Benefit Limit",
      "sub_category": "Frequency",
      "appeal_overturn_rate": 0.42,
      "sample_size": 847,
      "confidence_interval": [0.39, 0.45],
      "payer_variance": 0.08
    },
    ...
  ],
  "total_count": 47,
  "last_updated": "2026-04-14T12:00:00Z"
}

Filter by Category

GET /api/registries/denial-reasons?category=Administrative

Returns all 16 administrative codes, sorted by overturn rate (descending).

Filter by Overturn Rate

GET /api/registries/denial-reasons?overturn_min=0.65

Returns high-confidence codes (AUTH_REQUIRED, INELIGIBLE_MEMBER, AUTH_EXPIRED, etc.).

Search by Code or Description

GET /api/registries/denial-reasons?q=frequency

Returns FREQ_LIMIT, FREQ_INTENSITY, FREQ_SEASONAL (substring match on code + description).

Get Single Code Detail

GET /api/registries/denial-reasons/AUTH_REQUIRED

Response:

{
  "code": "AUTH_REQUIRED",
  "description": "Prior authorization required; not obtained before service",
  "category": "Administrative",
  "sub_category": "Prior Authorization & Auth-Adjacent",
  "appeal_overturn_rate": 0.73,
  "sample_size": 2341,
  "confidence_interval": [0.71, 0.75],
  "payer_variance": 0.06,
  "seasonal_q1_variance": -0.03,
  "seasonal_q2_variance": 0.00,
  "seasonal_q3_variance": 0.01,
  "seasonal_q4_variance": 0.04,
  "notes": "Highest-overturn denial code. Often payer error (auth request not received, incomplete info). Strong appeal grounds. Q4 spike to 76% due to year-end processing backlog.",
  "appeal_arguments": [
    "Provider submitted authorization request; payer has no record of receipt",
    "Payer requests were incomplete; provider resubmits with full information",
    "Service is time-sensitive; delaying for authorization denied patient access",
    "Prior authorization should be retroactive for emergency services"
  ],
  "related_codes": ["AUTH_EXPIRED", "AUTH_INCOMPLETE", "AUTH_CRITERIA"],
  "payer_specific_rates": {
    "Cigna": 0.75,
    "Aetna": 0.71,
    "UnitedHealthcare": 0.73,
    "Anthem": 0.70,
    "Medicaid": 0.76
  }
}

Query Cost Implications

All denial reason registry queries are free. The denial reason registry is reference data; queries do not require marketplace credits or consume cluster capacity. Typical use cases:
• Appeals intake: Look up denial code → fetch overturn rate and appeal arguments
• Precedent analysis: Filter precedents by denial reason code (uses precedent search, which IS charged)
• Cluster filtering: Marketplace queries on denial_reason_code field (charged normally)

Payer Variance

The same denial code can have significantly different overturn rates across payers. This reflects differences in appeal procedures, clinical review standards, and contractual appeal obligations.

Example: AUTH_REQUIRED across payers

Example: FUNCTIONAL_CAPACITY across payers

Implication: When analyzing appeal likelihood, filter precedents by payer AND denial reason code. Cigna's AUTH_REQUIRED (75%) is more predictive than Aetna's (71%).

Historical Trends

Overturn rates are stable year-over-year for most codes, but long-term trends show:
• Administrative codes declining (good news): AUTH_REQUIRED dropped from 78% (2023) → 73% (2026) as payers' auth processes improve
• Clinical codes stable: MED_NECESSITY, FUNCTIONAL_CAPACITY unchanged 2023–2026
• Q4 effect consistent: Year-end administrative spike appears every year (+2–3%)
• Benefit Limit codes declining: FREQ_LIMIT dropped from 46% (2023) → 42% (2026) as payers tighten review
Data sources: Stratum's internal precedent corpus (2023–2026), supplemented by academic studies (Milliman, Cigna appeals reports, state Medicaid data).

See also

• Payer Registry — Payer-specific appeal procedures and contact information
• Appeal Outcome Registry — Precedents with documented outcomes and appeal narratives
• Academic Research — Published studies on appeal overturn rates by condition
• Endpoints Validation — Denial code structure and ingest validation rules
• Precedent Objects — denial_reason_code field structure

Code reference

• src/registries/denial-reasons.json — Master registry data (47 codes, payer variance, seasonal patterns)
• src/services/denial-ingester.ts — Ingest validation (maps inbound X12 codes → denial reason codes)
• src/routes/registries.ts — Query endpoints (GET /api/registries/denial-reasons)
• tests/registries/denial-reasons.test.ts — Query tests and payer variance examples
• stratum-corpus-data/registries/denial-reasons.json — Canonical source (synced to platform via CI)

Appendix: Glossary

Term	Definition
Denial code	Unique 2–3 word identifier (e.g., FREQ_LIMIT, AUTH_REQUIRED) used to tag denials at ingest time
Appeal overturn rate	Historical percentage of appeals filed for this denial type that result in approval or partial coverage approval (range 0–100%)
Payer variance	How much the overturn rate for a given denial code varies across different payers (e.g., AUTH_REQUIRED may be 73% at Cigna but 68% at Aetna)
Seasonal pattern	Tendency for overturn rates to shift by quarter or calendar period (e.g., Q4 often sees higher administrative errors)
Category	Primary classification: Benefit Limit, Clinical Justification, or Administrative
Sub-category	Secondary classification within a primary category (e.g., Benefit Limit subdivided into Frequency, Duration, Visits)
Code	Description	Overturn Rate	Notes
FREQ_LIMIT	Service frequency exceeds plan limits	42%	Challenged with visit logs + functional gain evidence. Medicaid 48%, MA 37%.
FREQ_INTENSITY	Requested intensity higher than plan allows	45%	Functional improvement from baseline justifies higher frequency. Good appeal candidate.
FREQ_SEASONAL	Seasonal frequency cap exceeded	51%	Seasonal variations in need (winter PT, summer speech) often upheld on appeal.
Code	Description	Overturn Rate	Notes
DUR_LIMIT	Episode length exceeds plan maximum	39%	Lowest-overturn benefit-limit code; payers view this as defined plan boundary.
DUR_INTERIM	Interim episode denial; plan does not cover consecutive episodes	44%	Rare code; mainly Medicare Advantage plans. Overturn if clinical break between episodes demonstrated.
DUR_CUMULATIVE	Cumulative duration (lifetime) limit exceeded	48%	High overturn (Medicaid), low overturn (commercial, 38%). Diagnosis-dependent.
Code	Description	Overturn Rate	Notes
VISIT_LIMIT	Total visits in episode exceeds plan cap	43%	Same evidence pattern as FREQ_LIMIT; often conflated at claim time.
VISIT_AUTH	Requested visits exceed authorized authorization amount	68%	Auth-adjacent; if auth was issued but fewer visits approved, appeal cites auth letter.
VISIT_OVERRIDE	Visits approved for limited conditions only	40%	Plan approved visits for specific diagnosis; claim is for different diagnosis. Tough to overturn.
Code	Description	Overturn Rate	Notes
MED_NECESSITY	Service not medically necessary for diagnosis	58%	Highest-overturn clinical code. Requires clinical evidence (assessment, functional decline, provider letter).
MED_NECESSITY_THRESHOLD	Service severity does not meet clinical threshold	52%	Similar to MED_NECESSITY but focused on intensity/acuity. Dual-diagnosis cases overturn 65%.
MED_NECESSITY_COMORBID	Comorbid condition does not justify additional service	48%	Payer denies second service because primary diagnosis alone doesn't support it. Requires integrated care narrative.
MED_NECESSITY_DECLINE	No functional decline documented to support continued service	55%	Absence of baseline measurement = vulnerability. Strong baseline + decline metrics = high overturn (68%).
Code	Description	Overturn Rate	Notes
FUNCTIONAL_CAPACITY	Patient functional capacity exceeds plan criteria	34%	Lowest-overturn code overall. Payer disagrees with clinician's functional assessment. Hard to challenge without independent eval.
FUNCTIONAL_IMPROVEMENT_PLATEAU	Functional improvement has plateaued; no further gains expected	41%	Payer claims "maintenance only" = not medically necessary. Overturn if new functional decline or goal change documented.
GAF_INSUFFICIENT	Global Assessment of Functioning score insufficient to justify service	45%	DSM-5-era code; mainly behavioral health. Overturn if updated GAF + clinical narrative provided.
FUNCTIONALITY_THRESHOLD	Patient's current functional level does not meet service-specific threshold	37%	Variant of FUNCTIONAL_CAPACITY. PT denies because patient "too functional"; OT/speech similar patterns.
Code	Description	Overturn Rate	Notes
CLINICAL_THRESHOLD	Clinical parameters do not meet condition-specific standards	46%	Payer uses proprietary algorithm (e.g., pain score, ROM, grip strength). Overturn requires clinician challenge + new metrics.
EVIDENCE_INSUFFICIENT	Clinical evidence insufficient to support necessity claim	50%	Broadest clinical code. Often paired with specific missing documentation (evals, progress notes). Highest overturn when provider submits missing docs.
EVIDENCE_CONTRADICTORY	Submitted clinical evidence contradicts medical necessity claim	38%	Payer found conflicting info in chart (e.g., "no pain" in note vs. "high pain" in appeal). Hard to overturn without chart clarification.
TREATMENT_STANDARD	Treatment approach does not align with clinical guidelines	51%	Evidence-based practice challenge. Overturn if clinician references guideline alternative or clinical rationale.
TREATMENT_STANDARD_DEVIATION	Treatment deviates from condition-specific clinical pathway	47%	Specialty-driven (e.g., SLP pursuing non-standard aphasia protocol). Overturn if peer-reviewed evidence provided.
Code	Description	Overturn Rate	Notes
AUTH_REQUIRED	Prior authorization required; not obtained before service	73%	Highest-overturn code. Often payer error (auth request not received, incomplete info). Strong appeal grounds.
AUTH_EXPIRED	Prior authorization request expired; claim filed after expiration	71%	Payer-side timing issue. High overturn if expiration window was brief or provider had no notification.
AUTH_CRITERIA	Request submitted; does not meet plan's authorization criteria	65%	Payer rejected auth request itself (not claim denial). Overturn if criteria are vague or discriminatory.
AUTH_INCOMPLETE	Authorization request incomplete; additional information required	68%	Payer never fully reviewed. High overturn when provider resubmits complete request.
AUTH_MISMATCH	Service provided differs from authorized service	62%	Payer authorized different modality, frequency, or provider type. Overturn if claim aligns with intent of auth.
Code	Description	Overturn Rate	Notes
INELIGIBLE_MEMBER	Member not eligible for coverage on service date	72%	Second-highest overturn. Often retroactive coverage issue or lag in eligibility system. Verify member roster.
INELIGIBLE_EMPLOYEE	Employee not eligible under plan (spouse/dependent coverage issue)	61%	Eligibility records out of sync. Overturn if member proves enrolled.
INELIGIBLE_SERVICE	Service not covered under member's specific plan	58%	Member enrolled in plan that excludes service type (e.g., "behavioral health only" plan). Hard to overturn; need plan change.
Code	Description	Overturn Rate	Notes
CRITERIA_MISMATCH	Claim does not match payer's internal criteria for this service	69%	Vague payer criteria; often applies to newer service codes. Overturn if provider demonstrates alignment.
TIMELY_FILING	Claim filed outside timely filing window	64%	Payer deadline missed. Overturn if provider demonstrates good-faith timely filing effort or retroactive waiver request.
DUPLICATE_CLAIM	Claim is duplicate of previously paid claim	47%	Billing system error or claimed twice intentionally. Low overturn; requires claims audit.
EOB_MISMATCH	Claim contradicts existing EOB or coverage determination	56%	Prior denial or coverage decision conflicts. Overturn if EOB was erroneous or circumstances changed.
Category	Avg Overturn	Range	Interpretation
Administrative	65%	47–73%	Highest confidence; many are procedural failures
Clinical Justification	47%	34–58%	Medium confidence; requires clinical evidence
Benefit Limit	43%	39–51%	Lowest confidence; plan-boundary issues hard to challenge
Quarter	Pattern	Example
Q1	Administrative denials dip (-3%); payers enforce stricter controls post-January benefit resets	AUTH_REQUIRED drops to 70%; MED_NECESSITY spikes as clinical scrutiny increases
Q2	Stable; baseline rates hold	Average quarter; use as reference point
Q3	Slight administrative leniency (+1–2%)	Staffing vacations; simpler denials approved more often
Q4	Highest administrative errors (+2–3%); year-end processing backlog	AUTH_REQUIRED spikes to 76%; timely filing denials (+5%)
Payer	Overturn Rate	Notes
Medicaid	76%	Highest; state-level appeals processes more rigorous
Cigna	75%	Proactive appeals; fast turnaround
UnitedHealthcare	73%	Standard; large sample size
Aetna	71%	Stricter on auth timing; lower appeal success
Anthem	70%	Lowest; stringent re-review standards
Payer	Overturn Rate	Notes
Medicare Advantage	28%	Stricter functional standards; lowest overturn
Commercial (Cigna, Aetna)	35–38%	Moderate; some clinical flexibility
Medicaid	42%	Highest; more favorable to provider perspective
Term	Definition
Appeal overturn rate	Percentage of appeals filed for a given denial code that result in approval or partial approval
Confidence interval	95% CI around overturn rate (e.g., 0.39–0.45 for FREQ_LIMIT); indicates statistical reliability
Payer variance	Standard deviation of overturn rate across different payers; high variance (0.08+) indicates payer-dependent outcomes
Seasonal variance	Deviation from annual average in a given quarter (e.g., Q4 AUTH_REQUIRED +0.04 = 73% → 77%)
Sample size	Number of appeals analyzed to calculate overturn rate (higher = more reliable); minimum 100 for inclusion
Sub-category	Secondary classification within primary category (e.g., "Frequency" under "Benefit Limit")
Timely filing	Claim must be submitted within payer's deadline (typically 90–365 days); failure triggers TIMELY_FILING denial
Dual-diagnosis	Patient has two primary diagnoses; MED_NECESSITY_COMORBID denials common; overturn rate 48%