12.2 Emergency Department and Observation Services

The COC exam tests facility outpatient coding, but Evaluation and Management (E/M) still sits in the 13-question CPT domain. Hospital claims and professional claims are not interchangeable. The hospital bills the UB-04 (CMS-1450) with revenue codes. The physician or qualified health professional (QHP) bills the CMS-1500. Both may describe the same emergency department (ED) encounter with CPT codes 99281-99285, yet the documentation standard, the payment system, and sometimes the code set diverge by payer.

Emergency department E/M codes that are still in use

Type A hospital emergency departments — facilities that operate 24 hours a day, seven days a week — report facility ED visits with CPT 99281-99285. Those codes remain the facility ED visit codes under the Medicare Hospital Outpatient Prospective Payment System (OPPS). Pair them with an ED revenue code, most often 0450 (emergency room, general classification), unless the chargemaster uses a more specific 045x subcategory that still identifies an ED visit.

Type B emergency departments — dedicated emergency departments that are not 24-hour operations — report facility visits with HCPCS G0380-G0384 rather than 99281-99285. Do not put a Type B G-code on a professional claim, and do not put G0463 (hospital outpatient clinic visit) on an ED encounter merely because the patient was "seen in the hospital."

On the physician or QHP professional claim, beginning with the 2023 CPT E/M revisions, ED visit levels 99282-99285 are selected by medical decision making (MDM), not by history and examination bullet counts, and not by time. CPT continues to treat time as not a descriptive component for ED E/M levels because emergency care is typically delivered at variable intensity across several patients. Time is used for critical care (99291-99292) and, when the category allows it, for hospital inpatient or observation professional E/M. It is not the professional ED leveling pathway.

For professional reporting, 99281 is the lowest ED level. Its descriptor allows an ED E/M that may not require the presence of a physician or other QHP. 99282 requires straightforward MDM, 99283 low MDM, 99284 moderate MDM, and 99285 high MDM, each with a medically appropriate history and/or examination. Do not copy a copyrighted MDM grid into your notes. The CPT E/M guidelines in your book define MDM through three elements: the number and complexity of problems addressed, the amount and/or complexity of data reviewed and analyzed, and the risk of complications, morbidity, or mortality of patient management. The professional visit level is based on two of those three elements. When an exam item asks for the physician or QHP level, open the official MDM guidance in the CPT E/M guidelines rather than reconstructing a table from memory.

Facility leveling versus CPT definitions

CMS does not prescribe one national hospital ED facility-leveling method. Medicare Claims Processing Manual, Chapter 4, section 160 instead instructs each hospital to create and follow its own written guidelines based on hospital resources such as nursing interventions, tests, treatments, monitoring, and supplies. The guidelines must reasonably relate resource intensity to the reported levels, be consistently applied, follow hospital coding principles, and not facilitate upcoding. A physician's CPT MDM level therefore does not directly set the hospital facility level. A resource-based tool associated with the American College of Emergency Physicians (ACEP) may inform a hospital policy, but the hospital's adopted guidelines and facility record control.

Professional ED coding on the CMS-1500 uses the same 99281-99285 series for Type A settings, with MDM as the level driver. Facility and professional levels are not required to match, because they measure different things (hospital resources versus physician or QHP work), but both must be supported by the record.

Observation: CPT codes versus Medicare facility payment

Keep three rule sets separate.

CPT hospital inpatient and observation care E/M codes (99221-99223 initial, 99231-99233 subsequent, 99234-99236 same-date admission and discharge, plus discharge-day codes) describe professional E/M when a physician or QHP provides hospital inpatient or observation care. Those 2023 combined hospital inpatient and observation descriptors live in the E/M section of CPT. They are the usual professional-claim codes. They are not the Medicare hospital's hourly observation HCPCS code.

Medicare hospital facility observation is reported with HCPCS G0378 (hospital observation service, per hour) on the UB-04, typically with revenue code 0762. Direct referral to observation, when the patient is not seen in the hospital clinic or ED first, uses G0379 in addition to G0378 on the same date.

Medicare payment for a qualifying extended assessment and management encounter is the Comprehensive Observation Services comprehensive Ambulatory Payment Classification (C-APC) 8011, status indicator J2. CMS Medicare Claims Processing Manual, Chapter 4, and the OPPS C-APC policy (continued in the calendar year 2026 OPPS final rule, which still lists one Observation Services J2 APC) require all of the following for C-APC 8011:

1. Units of G0378 equal or exceed 8 hours.
2. A qualifying visit on the same date as G0378 or the day before: a Type A or Type B ED visit (99281-99285 or G0380-G0384), a hospital outpatient clinic visit (G0463), critical care (99291), or a same-date direct referral G0379.
3. The claim does not contain a procedure assigned status indicator T (separately paid surgical procedure subject to multiple-procedure reduction) or J1 (other comprehensive APC primary service).

If observation lasts fewer than 8 hours, hospitals still document and may report G0378, but Medicare does not pay the J2 composite. Payment stays with the separately payable visit (ED, clinic, or critical care), and observation is packaged. Observation after a T-status surgical procedure is treated as recovery, not as payable observation.

Observation start and stop times are clock times in the record that match a physician order to begin observation and the end of clinical interventions, including wrap-up after a discharge or inpatient-admission order. Report the hours as G0378 units, rounded per CMS instruction to the nearest hour, on one line. If care crosses calendar days, the date of service is the date observation began.

Eight hours versus midnight

The 8-hour threshold is an OPPS payment rule for C-APC 8011. It is not a CPT descriptor, and it is not a requirement that the patient remain past midnight. The CMS Two-Midnight Rule is an inpatient admission and status rule: when the physician expects medically necessary hospital care spanning at least two midnights, inpatient admission is generally appropriate. It does not convert an 8-hour observation stay into an inpatient stay, and it does not replace G0378 unit counting.

Some commercial payers use their own observation hour rules or require the stay to cross midnight before they pay an observation rate. Those are contract and payer-policy rules. They are not CPT. On the exam, identify the payer in the stem. For Medicare facility observation, count G0378 hours and test the J2 criteria. For professional observation E/M, use the CPT hospital inpatient and observation codes and the MDM-or-time instructions in that subsection of your book.

Scenario

A Medicare patient presents to a Type A ED with chest pain. The ED physician documents moderate MDM, while the hospital's documented internal guideline independently assigns facility level 99284 from the recorded nursing interventions and resources. The physician places the patient in hospital observation. Nursing records 10 hours of ordered observation. No T-status surgery is performed. The facility claim includes 99284 with revenue 0450, G0378 × 10 with revenue 0762, and diagnostic tests. That claim meets the 8-hour J2 pattern: qualifying ED visit, eight or more units of G0378, and no T or J1 procedure. The professional claim reports ED E/M and, if a physician provides observation care, the appropriate CPT observation or hospital E/M codes per CPT and payer rules — not G0378, which is a facility hourly HCPCS code.