CPT code 00320 identifies anesthesia services rendered for all surgical or interventional procedures performed on the esophagus, thyroid, larynx, trachea, and lymphatic system of the neck in patients one year of age or older. Maintained by the American Medical Association (AMA) and classified within the anesthesia code range 00100–01999, it carries 6 base units under the ASA Relative Value Guide and the CMS anesthesia base unit table. This code is time-based, meaning total reimbursement is calculated by combining base units with time units and multiplying by a geographic conversion factor — a formula that distinguishes anesthesia billing from nearly every other CPT category.
What Does CPT Code 00320 Mean?
CPT 00320 describes anesthesia care — including preoperative evaluation, induction, maintenance, and emergence — provided by a qualified anesthesia practitioner for any procedure performed on the cervical neck organs when the patient is at least one year old. The “not otherwise specified” designation in its descriptor means this is the default catch-all code for neck organ anesthesia unless a more specific code (00322 or 00326) applies.
Key attributes of this code at a glance:
- Billable status: Active; no descriptor changes since January 1, 2003
- Setting: Hospital operating room, ambulatory surgical center (ASC), or other procedural suite
- Eligible providers: Anesthesiologist (MD/DO), Certified Registered Nurse Anesthetist (CRNA), Anesthesia Assistant (AA) under medical direction
- Age restriction: Patient must be age 1 year or older at time of surgery
- Base units (ASA/CMS): 6
- MIPS participation: Yes — included in the Merit-Based Incentive Payment System
- Code added: January 1, 1990; last descriptor update January 1, 2003
What Procedures and Services Does CPT 00320 Cover?
CPT 00320 applies broadly to anesthesia administered for any surgical, endoscopic, or interventional procedure involving the following anatomic structures:
- Esophagus — including esophagoscopy, esophageal dilation, and esophageal tumor excision
- Thyroid gland — including thyroidectomy (partial or total), thyroid lobectomy, and thyroid mass excision (excluding needle biopsies; see 00322)
- Larynx — including laryngoscopy (direct or suspension microlaryngoscopy), laryngeal tumor resection, and vocal cord procedures (in patients ≥1 year)
- Trachea — including tracheostomy, tracheal resection, and tracheal reconstruction (in patients ≥1 year)
- Lymphatic system of the neck — including cervical lymph node dissection, sentinel lymph node biopsy of the neck, and radical neck dissection
These procedures are predominantly performed under general endotracheal anesthesia, though monitored anesthesia care (MAC) may apply in selected cases.
What Does CPT 00320 Specifically Exclude?
- Needle biopsy of the thyroid — Report CPT 00322 instead (3 base units)
- Larynx/trachea procedures in children younger than 1 year — Report CPT 00326 instead (7 base units)
- Procedures on the cervical spine and cord — Report CPT 00600, 00604, or 00670 as appropriate
- Procedures on major vessels of the neck — Report CPT 00350 (10 base units) or 00352 (5 base units)
- General head/neck/posterior trunk surface procedures not involving neck organs — Report CPT 00300 (3 base units)
When Is CPT 00320 the Right Code to Use?
Correct selection of 00320 requires satisfying all of the following criteria in sequence:
- Confirm the patient is age 1 year or older at the time of the surgical procedure. Infants under 12 months with laryngeal or tracheal procedures require 00326.
- Confirm the surgical site involves a neck organ — esophagus, thyroid, larynx, trachea, or cervical lymphatic system — not the cervical spine, major vessels, or surface/skin only.
- Confirm no more-specific anesthesia code applies. If the only procedure is needle biopsy of the thyroid, 00322 (3 base units) takes precedence. If larynx/trachea procedures are performed on an infant under 12 months, 00326 (7 base units) applies.
- Confirm the anesthesia practitioner provided the complete anesthesia care package — preoperative evaluation, induction, maintenance monitoring, and emergence/post-anesthesia care. Procedural sedation billed separately by the operating surgeon uses different CPT codes (99151–99153).
- Confirm the anesthesia record captures actual start and stop times in minutes, which is required for time-unit calculation under both Medicare and most commercial payers.
How Does CPT 00320 Differ From CPT 00322, 00326, and 00300?
| Code | Procedure Scope | Age Requirement | Base Units | Key Distinction |
|---|---|---|---|---|
| 00300 | Head, neck, posterior trunk surface | Any age | 3 | Surface/integumentary; does NOT include neck organs |
| 00320 | Esophagus, thyroid, larynx, trachea, cervical lymphatics | ≥1 year | 6 | Default neck organ anesthesia; broadest scope |
| 00322 | Esophagus, thyroid, larynx, trachea, cervical lymphatics — needle biopsy of thyroid only | ≥1 year | 3 | Procedure-specific carve-out for thyroid needle biopsy |
| 00326 | Larynx and trachea procedures | <1 year | 7 | Age-specific code for infants; higher base units reflect added complexity |
In practice, the most common coding error for this family is reporting 00320 for a pediatric patient under age 1 undergoing laryngoscopy or tracheoscopy — a mismatch that triggers claim denial because payers validate the age threshold against the date of birth on file. When the surgical note documents a thyroid fine-needle aspiration biopsy in an adult, 00322 is always the more specific and correct choice, and it carries a lower base unit value (3 vs. 6).
What Documentation Is Required to Support CPT 00320?
Anesthesia claims do not use the familiar E/M documentation frameworks. Instead, they rely on the anesthesia record as the primary claim support document. For CPT 00320, that record must substantiate the full anesthesia care package.
What Must the Provider Document in the Anesthesia Record?
The seven-element anesthesia care package required by CMS Medicare Claims Processing Manual, Chapter 12, Section 50 must each be evidenced in the anesthesia record:
- Pre-anesthetic examination and evaluation — A documented assessment of the patient’s airway, physical status (P1–P6), relevant comorbidities, and anesthesia risks before the procedure begins
- Anesthesia plan — The type of anesthesia selected (general endotracheal, MAC, regional, TIVA) and the rationale documented in the pre-op note
- Personal participation in induction and emergence — For anesthesiologists billing modifier AA or directing CRNAs under QK/QY, the record must confirm the anesthesiologist was personally present during the most demanding phases
- Anesthesia start time and stop time in minutes — Required by Medicare and most commercial payers; time is recorded from when the provider begins preparing the patient for induction through when the patient can be safely transferred to post-anesthesia care
- Intraoperative monitoring entries — Vital signs, ventilator settings, drug administration, fluid management, and any intraoperative events documented at frequent intervals
- Provider identity and role — Clear documentation of who administered and/or medically directed the anesthesia (anesthesiologist, CRNA, AA) and the applicable modifier basis
- Post-anesthesia note — Documentation of the patient’s condition at handoff and any post-procedure complications or monitoring instructions
What Are the Documentation Standards for Facility vs. Non-Facility Settings?
| Requirement | Hospital/ASC (Facility) | Office-Based Surgical Suite (Non-Facility) |
|---|---|---|
| Anesthesia record format | Intraoperative flowsheet (paper or EHR) | Same — paper or EHR-based anesthesia flowsheet |
| Pre-op evaluation | Documented in hospital pre-admission or same-day pre-op note | Documented in the practice’s pre-op assessment form |
| Time documentation | Anesthesia start/stop in minutes; required | Anesthesia start/stop in minutes; required |
| Monitoring documentation | Required; standard hospital monitoring | Required; provider must document monitoring equipment present |
| State-specific requirements | Follow hospital bylaws and state board rules | Office-based anesthesia regulations vary significantly by state |
How Does CPT 00320 Affect Medical Billing and Reimbursement?
Unlike standard CPT codes reimbursed by a flat fee schedule rate, anesthesia reimbursement follows the Standard Anesthesia Formula:
Payment = (Base Units + Time Units) × Conversion Factor × Modifier Percentage
For CPT 00320 with 6 base units, a 90-minute procedure generates 6 time units (90 ÷ 15 = 6). Total units = 12. Multiplied by the applicable anesthesia conversion factor, the dollar allowable is calculated. Note that CMS anesthesia conversion factors vary by geographic locality (GPCI-adjusted), and the CMS base units for 00320 have remained at 6 and have been unchanged through CY 2025 per the CMS Anesthesiologists Center.
| Billing Component | CPT 00320 Value | Notes |
|---|---|---|
| Base units (ASA/CMS) | 6 | Fixed; unchanged CY 2025 |
| Time units | Variable | 1 unit per 15 minutes (Medicare); some payers use 10- or 12-minute intervals |
| Example: 90-min case | 6 base + 6 time = 12 total units | Before modifier percentage applied |
| Medicare conversion factor | ~$21–23/unit (locality-adjusted) | Verify current rate via CMS Physician Fee Schedule lookup |
| Commercial conversion factor | Typically $70–$85+/unit | Varies significantly by payer contract |
| Facility vs. non-facility rate | Same formula; payer contract may differ | No separate facility/non-facility RVU split for anesthesia codes |
Billing teams should confirm the current locality-adjusted conversion factor annually via the CMS Anesthesia Conversion Factors ZIP files published on the CMS Anesthesiologists Center page.
What Modifiers Are Commonly Used With CPT 00320?
| Modifier | Description | When to Apply | Billing Impact |
|---|---|---|---|
| AA | Anesthesia personally performed by an anesthesiologist | Anesthesiologist administers anesthesia without CRNA involvement | 100% of allowed amount |
| QK | Medical direction of 2–4 CRNAs or AAs by an anesthesiologist | Anesthesiologist directs multiple concurrent CRNA cases | 50% of allowed amount per case |
| QY | Medical direction of one CRNA by an anesthesiologist | Anesthesiologist directs a single CRNA | 50% of allowed amount |
| QX | CRNA service with medical direction by a physician | CRNA billing under physician direction | 50% of allowed amount |
| QZ | CRNA service without medical direction by a physician | CRNA billing independently (where state law permits) | 100% of allowed amount |
| AD | Medical supervision of >4 concurrent CRNA cases | Anesthesiologist supervises (not directs) >4 concurrent cases | 3 base units + 1 unit if present at induction |
| P1–P6 | Physical status modifiers | Required to report patient health status; informational under Medicare | Medicare: informational only; some commercial payers add units for P3+ |
| +99100 | Qualifying circumstance: extreme age (patient ≥70 or <1 yr) | Patient age 70 or older | Adds 1 additional base unit; list separately |
| QS | Monitored anesthesia care (MAC) | Anesthesia provided as MAC rather than general | Required by many payers; MAC policies vary |
| 23 | Unusual anesthesia | General anesthesia required for procedure normally done under local | Informational; no additional payment |
| 47 | Anesthesia by surgeon | Surgeon personally performs regional/general anesthesia for own case | Append to surgical code; no separate anesthesia claim |
Important: Medicare and most commercial payers require an anesthesia provider modifier (AA, QK, QX, QY, QZ, or AD) in the first modifier position on every anesthesia claim. Missing this modifier is one of the leading causes of anesthesia claim rejection.
Are There Qualifying Circumstances or Coverage Restrictions That Apply?
- Add-on code +99100 applies when the patient is age 70 or older — a frequent oversight in practices billing 00320 for adult thyroidectomy and neck dissection patients. This adds 1 qualifying circumstance unit and must be listed separately on the claim. Note that 00326 (children under age 1) already incorporates the infant age complexity in its higher base unit value; do not also report +99100 for infants billed under 00326.
- Medicare medical necessity: Although 00320 is a broad anesthesia code, the underlying surgical procedure must be medically necessary. Claims should pair 00320 with the appropriate ICD-10-CM diagnosis code from the surgical team’s documentation.
- MAC billing: When anesthesia for a neck organ procedure is provided as MAC (e.g., for a monitored cervical lymph node biopsy), append modifier QS and ensure the clinical record supports the decision for monitored rather than general anesthesia.
- No prior authorization for the anesthesia code itself is typically required, but the underlying surgical procedure may require prior authorization from commercial payers.
What CPT or HCPCS Codes Are Commonly Billed Alongside CPT 00320?
When a patient undergoes a neck organ procedure, the anesthesia provider bills 00320 (or its family members) while the surgeon bills the operative CPT code. The anesthesia claim and surgical claim are filed separately on separate claim forms.
| Associated/Surgical Code | Description | Typical Pairing Context | Bundling Risk |
|---|---|---|---|
| 60100 | Biopsy, thyroid | Surgeon’s code for open thyroid biopsy; anesthesia = 00320 | No |
| 60240 | Thyroidectomy, total | Total thyroid removal | No |
| 60260 | Thyroidectomy, second stage | Re-operation; anesthesia complexity increases | No |
| 31530 | Laryngoscopy, direct, with foreign body removal | Laryngeal foreign body | No |
| 31580 | Laryngoplasty; for laryngeal web, with graft | Laryngeal reconstruction | No |
| 31600 | Tracheostomy, planned | Elective tracheotomy | No |
| 38720 | Cervical lymphadenectomy (radical) | Radical neck dissection | No |
| +99100 | Qualifying circumstance: extreme age | Patient ≥70 years undergoing 00320 procedure | Add-on; no edit |
| 01996 | Daily management of epidural or subarachnoid drug administration | Post-op pain management; NOT time-based | Not bundled with 00320; separate date of service |
Which Code Combinations Trigger NCCI or CCI Edits?
- Anesthesia codes (00100–01999) are globally bundled with routine pre/post-op monitoring, IV placement, and non-invasive physiologic monitoring. Do not separately bill for these services when 00320 is on the claim.
- Drug administration codes (96360–96379) cannot be separately reported for anesthetic agents or other drugs administered as part of the anesthesia service — per the CMS NCCI Policy Manual, Chapter 2.
- Moderate conscious sedation codes (99151–99153) cannot be billed by the anesthesia practitioner on the same claim as 00320 for the same service date.
- Monitoring catheter placement (e.g., CPT 36555–36556 for central venous access) cannot be separately reported by the anesthesia practitioner when the catheter is placed through the same site used for anesthesia monitoring purposes.
- Post-operative pain blocks placed before induction or after emergence do not add time to the reported anesthesia time for 00320; however, the block itself (e.g., a nerve block CPT code) may be separately reportable by the anesthesia provider under certain payer policies — verify with the specific payer.
What Coding Errors Should You Avoid With CPT 00320?
Anesthesia billing teams and credentialed coders (CANPC, CPC) consistently encounter the same clusters of errors with this code. Ranked by audit frequency and compliance risk:
- Reporting 00320 for a patient under age 1 — Payers validate date of birth against the procedure date. Infants undergoing larynx or trachea procedures require 00326 (7 base units). Using 00320 results in denial and potential overpayment if the claim is initially processed.
- Using 00320 instead of 00322 for thyroid needle biopsy — 00322 (3 base units) is the correct and lower-value code for this specific procedure. Billing 00320 (6 base units) for a thyroid FNA overstates the claim by 3 base units and is an audit target.
- Omitting the required anesthesia provider modifier — Every 00320 claim must carry AA, QK, QY, QX, QZ, or AD in the first modifier field. Claims submitted without a provider modifier are routinely rejected.
- Reporting anesthesia time in hours rather than minutes — Medicare requires anesthesia time in actual minutes, converted to time units. Rounding to the nearest 15-minute mark rather than using actual minutes may understate or overstate units.
- Failing to append +99100 for patients age 70 or older — This qualifying circumstance code adds 1 base unit and is a legitimate revenue enhancement. Omitting it leaves reimbursement on the table; incorrectly adding it when the patient is under 70 is a compliance risk.
- Billing separate monitoring or IV codes alongside 00320 — Pre- and post-op care, IV line placement, and non-invasive monitoring are bundled into the anesthesia code and cannot be separately reported.
- Reporting 00320 for procedures on the cervical spine — Cervical spine and cord procedures use codes 00600, 00604, or 00670. Using 00320 for a cervical spine fusion is a misuse of the neck organ code family.
What Do Auditors Look for When Reviewing CPT 00320 Claims?
- Age validation: Payer systems cross-check the patient’s date of birth against the procedure date. Mismatches between patient age and code selection (00320 vs. 00326) are flagged automatically.
- Provider modifier logic: Claims billing at 100% (modifier AA or QZ) are cross-checked against concurrent case logs. If a provider billed AA while simultaneously directing other cases, medical direction modifiers (QK/QY) apply instead.
- Time documentation: Auditors compare the anesthesia record’s start/stop times against the OR log and recovery room admission time. Gaps or inconsistencies are red flags under Recovery Audit Contractor (RAC) reviews.
- Appropriate qualifying circumstance add-ons: OIG Work Plan focus areas have historically included improper use of qualifying circumstance codes. Ensure +99100 is applied only when the patient meets the documented age threshold.
- Base unit alignment with the surgical procedure: The ASA Crosswalk assigns specific surgical CPT codes to anesthesia codes. If the surgical code on the facility or professional claim does not logically crosswalk to 00320, payers may request medical record review.
How Does CPT 00320 Relate to Other CPT Codes in the Neck Anesthesia Family?
CPT 00320 is the parent “catch-all” code within the neck organ anesthesia subfamily. Understanding its position in the family prevents both undercoding and overcoding.
| Related Code | Relationship | Base Units | Key Distinction |
|---|---|---|---|
| 00300 | Adjacent — different anatomic scope | 3 | Head/neck surface; NOT neck organs |
| 00320 | Primary code (this code) | 6 | Default neck organ anesthesia, age ≥1 |
| 00322 | Procedure-specific carve-out | 3 | Thyroid needle biopsy only; lower intensity |
| 00326 | Age-specific carve-out | 7 | Larynx/trachea, age <1 year; higher intensity |
| 00350 | Adjacent — vascular scope | 10 | Major neck vessel surgery; not neck organs |
| 00352 | Adjacent — vascular scope | 5 | Simple ligation of neck vessel |
| +99100 | Add-on qualifying circumstance | +1 | Extreme age (≥70); listed separately with 00320 |
What Is the Correct Reporting Order When CPT 00320 Appears With Add-On Codes?
- Report CPT 00320 as the primary anesthesia code with the appropriate provider modifier (AA, QK, etc.) in the first modifier position.
- If the patient is age 70 or older, list add-on code +99100 on a separate line of the claim form, referencing the same date of service.
- If the case involves MAC, add modifier QS in the next available modifier position on the 00320 line.
- Physical status modifiers (P1–P6) are informational; append to the 00320 line per payer instructions, typically after the required provider modifier.
- When multiple surgical procedures are performed during one anesthesia encounter, report only the anesthesia code with the highest base unit value as the primary anesthesia code. Report time as the combined total for the entire session. Do not bill multiple anesthesia codes for the same session at full base unit value.
Real-World Coding Scenario — How CPT 00320 Is Applied in Practice
Clinical Encounter: A 74-year-old male with a multinodular goiter and airway compression undergoes a total thyroidectomy performed at a hospital outpatient surgical suite. The anesthesiologist performs a pre-operative airway evaluation documenting a Mallampati Class III airway, establishes the anesthesia plan (general endotracheal anesthesia with video laryngoscope anticipated), and is personally present for induction and emergence. Anesthesia time is 112 minutes. The anesthesiologist did not direct any concurrent CRNA cases.
Correct Code Application
- Primary anesthesia code: CPT 00320 — Anesthesia for all procedures on esophagus, thyroid, larynx, trachea, and lymphatic system of neck; age 1 year or older
- Provider modifier: Modifier AA — Anesthesia personally performed by anesthesiologist
- Physical status modifier: Modifier P3 — Patient with severe systemic disease (multinodular goiter with airway compromise; likely hypertension and other comorbidities documented)
- Add-on qualifying circumstance: CPT +99100 — Patient age 74, meeting the ≥70 threshold
- Time units: 112 minutes ÷ 15 = 7.47 → 7.5 time units (Medicare rounds to one decimal)
- Total units billed: 6 (base) + 7.5 (time) + 1 (99100) = 14.5 units
Common Mistake in This Scenario
- Error: Billing CPT 00320-AA without appending +99100, despite the patient being 74 years old
- Why it fails: The practice leaves 1 qualifying circumstance unit unbilled — a recurring revenue leak that compounds across a high-volume thyroid surgery practice
- Second common error: Appending modifier P3 in the first modifier position rather than the required provider modifier (AA). Payers expect the provider modifier (AA) first; misplacing P3 in position 1 causes claim rejection at the modifier validation edit level
Frequently Asked Questions About CPT Code 00320
Is CPT Code 00320 Still Valid for Use in 2025 and 2026?
CPT code 00320 remains a fully active, billable anesthesia code with no changes to its descriptor or base unit value through at least CY 2025, as confirmed by the CMS Anesthesia Base Units table. Coders should verify annually against the current AMA CPT Professional Edition and the CMS Anesthesiologists Center base unit files to confirm the code remains unchanged for CY 2026.
What Is the Difference Between CPT 00320 and CPT 00326?
CPT 00320 is used for anesthesia during larynx and trachea procedures in patients age 1 year or older, while CPT 00326 is the age-specific code for the same anatomic region in patients younger than 1 year of age. The key differentiator is solely the patient’s age at the time of surgery — not the procedure type, anesthesia method, or clinical complexity. CPT 00326 carries 7 base units versus 00320’s 6 base units, reflecting the additional anesthetic complexity involved in pediatric airway cases on infants.
How Is Anesthesia Time Calculated and Reported for CPT 00320?
Anesthesia time for 00320 begins when the anesthesia provider starts preparing the patient for induction and ends when the patient can safely be placed under post-anesthesia supervision. Under Medicare, this time is documented in actual minutes and converted to time units using a 15-minute interval (e.g., 90 minutes = 6 time units, calculated to one decimal place). Commercial payers may use 10- or 12-minute intervals, so biller teams should verify each payer’s time unit convention separately.
Can a CRNA Bill CPT 00320 Independently Without Physician Direction?
Yes, a CRNA may bill CPT 00320 independently in states where opt-out of the physician supervision requirement is in effect, using modifier QZ (CRNA service without medical direction by a physician). In states without opt-out, the CRNA providing anesthesia under physician medical direction bills with modifier QX, while the directing anesthesiologist simultaneously bills with QY (if directing one CRNA) or QK (if directing 2–4 concurrent cases). State law and payer contracts govern which arrangement is permissible.
When Should +99100 Be Added to a CPT 00320 Claim?
Add-on code +99100 should be reported alongside CPT 00320 whenever the patient is age 70 years or older at the time of the procedure. It adds 1 qualifying circumstance unit to the claim, which increases the total unit count and thereby increases the reimbursed allowable. Note that Medicaid programs in some states do not recognize qualifying circumstance codes, so billers must verify the payer’s policy before submitting +99100.
What Happens if the Wrong Anesthesia Code Is Billed for a Neck Procedure?
Billing the wrong anesthesia code — for example, 00320 instead of 00322 for a thyroid needle biopsy, or 00320 instead of 00326 for an infant’s airway procedure — results in either a claim denial (age mismatch) or an overpayment (base unit mismatch). Overpayments identified in a RAC or payer audit trigger recoupment demands and, in systematic patterns, can result in compliance referrals. Anesthesia billing teams should implement a pre-submission crosswalk check comparing the surgical procedure code against the expected anesthesia code family to catch these errors before claim submission.
Does Medicare Cover CPT 00320 for All Neck Organ Procedures?
Medicare covers CPT 00320 when the underlying surgical procedure is medically necessary and performed in a covered setting by a covered provider. Because 00320 is the anesthesia code rather than the surgical code, coverage ultimately follows the surgical procedure’s medical necessity determination. Anesthesia billers should pair 00320 with the appropriate ICD-10-CM diagnosis code consistent with the surgeon’s operative documentation to prevent medical necessity denials.
Key Takeaways for Billing and Coding CPT 00320
- CPT 00320 is the default anesthesia code for all neck organ procedures (esophagus, thyroid, larynx, trachea, cervical lymphatics) in patients age 1 year or older, carrying 6 base units.
- Patient age is the critical branch point in this code family: use 00326 for patients under 1 year; use 00322 when the procedure is limited to a thyroid needle biopsy.
- Every CPT 00320 claim must include a required anesthesia provider modifier (AA, QK, QY, QX, QZ, or AD) in the first modifier position — claims submitted without this modifier will be rejected.
- Reimbursement follows the Standard Anesthesia Formula: (Base Units + Time Units) × Conversion Factor × Modifier Percentage. Base units are fixed at 6; time units vary by the actual anesthesia duration.
- Add-on code +99100 should be appended whenever the patient is age 70 or older — omitting it is one of the most common, easily preventable revenue leaks in anesthesia billing.
- Routine pre/post-op care, IV placement, and non-invasive monitoring are bundled into 00320 and cannot be separately billed on the same claim.
- Annual verification against the CMS Anesthesia Base Unit table and the AMA CPT Professional Edition ensures your team is current — anesthesia codes do not change frequently, but conversion factors update every calendar year.
For additional guidance on anesthesia modifier billing rules, NCCI bundling edits, and medical necessity documentation, review the CMS Medicare Claims Processing Manual, Chapter 12, Section 50, and the CMS NCCI Policy Manual, Chapter 2 (Anesthesia Services).
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