M1339 HCPCS Follow-Up Assessment Reimbursement

HCPCS Level II code M1339 captures a follow-up functional assessment performed 30 to 180 days after an index assessment when the patient demonstrates improvement or maintenance of functioning. The code aligns with value-focused measurement of patient outcomes and is relevant for programs that monitor functional recovery or stability over a defined performance period. Nationally, the code matters for payers and providers tracking longitudinal functional outcomes, quality reporting, and bundled or value-based payment arrangements.

Key payers in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find concise benchmarks for use frequency where available, context on typical service settings and clinical intent, and guidance on how the code fits into performance measurement workflows. The publication outlines clinical context for when a 30–180 day reassessment is indicated, discusses typical sites of service such as outpatient clinics and home health or ambulatory care, and summarizes common billing modifiers and administrative considerations. Data not available in the input is noted where applicable. This national overview provides operational clarity for revenue cycle, clinical leaders, and policy analysts who manage or evaluate outcome-based assessment coding.

Billing Code Overview

HCPCS Level II code M1339 describes patients who had a follow-up assessment 30 to 180 days after the index assessment and who demonstrated positive improvement or maintenance of functioning scores during the performance period. This code represents a performance or outcome-based assessment tied to longitudinal functional status tracking.

Service type: Follow-up functional assessment and outcome monitoring
Typical site of service: Outpatient clinic or home health/ambulatory care setting where periodic functional assessments are performed

Clinical Context

A typical patient is a 68-year-old Medicare beneficiary recovering from a stroke with documented functional deficits in mobility and activities of daily living. The patient receives an initial standardized functional assessment (index assessment) by a physical therapist or occupational therapist in an outpatient rehabilitation clinic or home health visit. A follow-up assessment is scheduled between 30 and 180 days after the index assessment to measure change or maintenance in functional status using the same standardized instruments (for example, FIM, Barthel Index, or an established CMS-approved functional outcome measure). The follow-up visit documents positive improvement or maintenance of functioning scores during the performance period compared to the index assessment and supports continued rehabilitation, discharge planning, or maintenance therapy.

Typical workflow:

Referral and intake with baseline functional assessment (index assessment) performed and scores documented.
Initiation of therapy interventions (physical therapy, occupational therapy, speech therapy as indicated) with documented goals and progress notes.
Scheduled follow-up assessment between 30 and 180 days post-index assessment using identical measurement tools; comparison of scores to demonstrate improvement or maintenance.
Documentation includes date of index assessment, date of follow-up, specific standardized instrument used, itemized scores, narrative interpretation of change (improved/maintained), and plan of care adjustments if applicable.
Billing uses HCPCS Level II code M1339 for the follow-up assessment that meets the timeframe and outcome criteria; relevant CPT services (evaluation, therapy visits) and appropriate modifiers are appended per payer rules.

Coding Specifications

Modifier	Description	When to Use
`22`	Increased procedural services	When the follow-up assessment requires substantially greater time and effort beyond typical requirements and documentation supports the increased service.

23 | Unusual anesthesia | Not typically applicable to functional follow-up but may be used in rare circumstances where anesthesia was required for assessment procedures.

52 | Reduced services | When a follow-up assessment is partially reduced or discontinued and the provider documents reduced service.

53 | Discontinued procedure | When the assessment was started but stopped due to patient instability or other documented reasons.

54 | Surgical care only | Not usually applicable to this assessment; relevant when only surgical care is billed separately.

55 | Postoperative management only | Use if only postoperative management is reported by a different provider than the surgeon; rarely used with this assessment.

56 | Preoperative management only | Rarely used; applicable when only preoperative management is billed by a different provider.

62 | Two surgeons | Use when two qualified providers share responsibility for care during an assessment that is part of a combined service.

AS | Physician assistant, nurse practitioner, or clinical nurse specialist services for Medicare beneficiaries | When a PA, NP, or CNS performs the follow-up assessment under their state scope and Medicare billing rules.

CO | New technology (or contractual obligation) — payer-specific | Applied per payer contractual requirements; use only when payer policy specifies.

CQ | Service furnished by a nurse practitioner/physician assistant/clinical nurse specialist in the Skilled Nursing Facility setting under the Medicare Part B benefit | When the follow-up assessment is furnished in an SNF by an NP/PA/CNS and payer requires this modifier.

FX | Single surgeon | Use when documentation clarifies a single surgeon performed the related services; rarely applied to assessments.

FY | Left via global surgery modifiers (provider-specific) | Not typically used for functional assessments; included if payer requires.

QK | Medical direction of two, three, or four concurrent anesthesia procedures | Not applicable to routine functional assessments; included for completeness when anesthesia services are part of the encounter.

QX | CRNA service with medical direction by a physician | See QK note; rarely relevant.

QY | Medical direction of one CRNA by an anesthesiologist | See QK note; rarely relevant.

Taxonomy Code	Specialty	Notes
`174100000X`	Physical Therapist	Most common provider performing standardized functional follow-up assessments in outpatient, SNF, and home health settings.

334800000X | Occupational Therapist | Frequently performs ADL-focused functional assessments and documents maintenance/improvement.

208D00000X | Physical Medicine & Rehabilitation Physician | Oversees rehabilitation plans, interprets outcomes, and coordinates ongoing care.

363L00000X | Speech-Language Pathologist | Performs functional communication and swallowing-related assessments when applicable.

367A00000X | Nurse Practitioner | Performs follow-up assessments in outpatient, home health, and SNF settings where scope allows and billing permits.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`I69.351`	Left hemiplegia following cerebral infarction, affecting dominant side	Post-stroke motor deficits commonly require baseline and follow-up functional assessments to document recovery or maintenance.

I69.391 | Hemiplegia and hemiparesis following unspecified cerebrovascular disease, affecting unspecified side | Typical neurological diagnosis prompting standardized functional follow-up to measure ADL independence.

M62.81 | Muscle weakness (generalized) | Generalized weakness from deconditioning or chronic illness often tracked with functional outcome measures.

S72.001A | Fracture of unspecified part of neck of right femur, initial encounter for closed fracture | Post-hip-fracture patients require functional assessments during rehabilitation to document progress.

R26.2 | Difficulty in walking, not elsewhere classified | Functional mobility limitation commonly assessed and monitored with standardized tools.

G81.90 | Hemiplegia, unspecified affecting unspecified side, unspecified | Broad stroke-related diagnosis that commonly triggers serial functional assessments.

M54.5 | Low back pain | Chronic musculoskeletal conditions that may require functional assessments to document response to rehabilitation interventions.

Z47.1 | Aftercare following joint replacement surgery | Routine follow-up assessments to document maintenance or improvement of function after major orthopedic procedures.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`97161`	Physical therapy evaluation, low complexity	Initial or subsequent therapy evaluation that may precede the index functional assessment and inform the plan of care.

97110 | Therapeutic exercises to develop strength and endurance, range of motion and flexibility | Common therapy treatment provided between index and follow-up assessments to improve functional scores.

97162 | Physical therapy evaluation, moderate complexity | Used for more complex initial evaluations that can serve as the index assessment documentation.

97164 | Re-evaluation of physical therapy established plan of care | Periodic re-evaluation that may coincide with or complement the standardized follow-up assessment billed with M1339.

97530 | Therapeutic activities, direct (one-on-one) patient contact | Functional task training frequently provided as part of rehabilitation between assessments.

99509 | Home visit for assessment and/or care coordination (example code — payer-specific) | Home-based assessment or care coordination visits that may accompany a home health follow-up functional assessment (note: use payer-specific guidance for home visit CPT codes).

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Summary & Overview

HCPCS Level II M1339: Follow-Up Functional Assessment (30–180 Days)