Summary & Overview
HCPCS Level II M1438: Time Last Known Well to Hospital Arrival ≤ 210 Minutes
HCPCS Level II code M1438 documents the time interval from a patient’s last known well state to hospital arrival of less than or equal to 3.5 hours (210 minutes). This time-sensitive measure is clinically important for acute stroke pathways, where arrival within specific time windows influences triage decisions, eligibility for time-dependent interventions, and quality reporting. Nationally, standardized documentation of last-known-well intervals supports performance measurement and care coordination across emergency and inpatient settings.
Key payers addressed include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the clinical meaning and service context for M1438, plus what to expect in payer coverage and typical use cases. The publication summarizes benchmarking approaches, common policy considerations affecting time-window documentation, and operational implications for emergency departments and stroke teams. It also outlines gaps where input data were not provided.
This summary is intended for clinicians, billing professionals, and policy analysts seeking a national perspective on the role of M1438 in acute stroke care documentation, reporting, and payer interactions.
Billing Code Overview
HCPCS Level II code M1438 indicates time last known well to hospital arrival less than or equal to 3.5 hours (<= 210 minutes). This code documents the interval from when a patient was last known to be symptom-free to their arrival at a hospital.
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Service type: Time interval documentation related to acute stroke/timely arrival assessment
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Typical site of service: Emergency department or acute inpatient hospital setting
Clinical & Coding Specifications
Clinical Context
A patient in their mid-60s is brought to the emergency department by ambulance after sudden onset of right-sided weakness and aphasia noted by family. Emergency medical services documents the patient was last known well 2 hours and 15 minutes prior to hospital arrival. On arrival the ED team performs a rapid stroke assessment, obtains emergent non-contrast head CT to exclude hemorrhage, and initiates stroke pathway evaluation including NIH Stroke Scale scoring, point-of-care labs, and IV access. Given that the time last known well to hospital arrival is within 210 minutes (≤ 3.5 hours), the patient is assessed for eligibility for acute ischemic stroke interventions such as intravenous thrombolysis per local protocol. Stroke neurology is consulted, imaging and lab results are reviewed for contraindications, and documentation captures the exact time last known well, time of ED arrival, and all decision points for reperfusion therapy consideration.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
24 | Unrelated evaluation and management service by the same physician during a postoperative period | Use when an E/M for stroke assessment is unrelated to a prior procedure and occurs during a global period |
25 |