A witness of a traffic accident called 911. An ambulance with emergency basic life support arrived at the scene of the accident. The injured party…

A0429 designates “Ambulance service, basic life support, emergency transport.”

Because the crew provided BLS care in response to a 911 call, the transport meets CMS’s definition of an emergency BLS run (CMS Pub-100-04, Ch. 15 §30.2).

Modifier pair −SH indicates origin Scene of accident (S) and destination acute-care Hospital (H) (§20.1).

Modifier QN is used when the ambulance is furnished directly by a provider of services (e.g., a hospital-based ambulance responding to 911) (§30.2.7).

Therefore the complete code is A0429-QN-SH.

A. A0426 is Advanced Life Support, non-emergency; does not match BLS or emergency nature.

C. A0427 represents ALS emergency; wrong service level and reversed destination modifier (-HS).

D. A0428 is BLS non-emergency and modifier order is reversed; does not describe an emergency response.

1. 2024 HCPCS Level II Professional Edition

A0426–A0429 code descriptors

p. 290.

2. Centers for Medicare & Medicaid Services (CMS). Medicare Claims Processing Manual

Pub 100-04

Ch. 15: “Ambulance

”

§20.1 Origin/Destination Modifiers; §30.2 Definition of Emergency vs. Non-Emergency Transport; §30.2.7 Modifiers QM & QN.

3. 42 CFR §410.40(b)(1) – Definition of BLS emergency ambulance services.