CPT Code 99358: Prolonged E/M Service Before and/or After Direct Patient Care, First Hour

What is a prolonged E/M service (before/after visit)?

A prolonged evaluation and management service before or after a direct patient encounter refers to the time a qualified health care professional spends on medically necessary tasks that support patient care but do not involve direct patient contact.

These services often involve pre-service time, such as reviewing external records before an office visit, or post-service activities like analyzing lab results and writing detailed care coordination notes.

CPT code 99358 documentation requirements

To report 99358 accurately, the provider must include specific elements in the medical record. Thorough and compliant documentation ensures that the prolonged service is justified, especially when billing payers such as Medicare.

Time spent on the service

Documentation must reflect the total time spent on non-face-to-face activities. A minimum of 31 minutes is required to report CPT 99358, and the total time must be clearly noted in the chart.

Description of the service

The medical record must specify what was done during the prolonged service. Examples include pre-visit extensive record review, post-visit diagnostic analysis, or coordination with external healthcare providers.

Medical necessity justification

The prolonged service must be clinically appropriate. The provider must explain why these additional services were necessary for the patient’s care and why they could not be performed during the standard face-to-face E/M service.

Separation from other services

The time reported for CPT 99358 must be distinct from any face-to-face time already reported under another E/M code. It cannot overlap with time billed on the same date using office visit codes or other direct patient services.

CPT code 99358 billing guidelines

Proper billing of CPT 99358 ensures accurate reimbursement while complying with the Medicare Physician Payment Schedule and commercial payer rules. Below are the key billing considerations.

Bill once per date of service

CPT 99358 is billed once for the first hour (minimum 31 minutes) of prolonged service time on a given date. It must be performed personally by the billing physician or qualified healthcare professional.

Use add-on code 99359 for additional time

If more than one hour of prolonged non-face-to-face service is provided, use add-on code 99359 to report each additional 30-minute increment. Ensure the documentation clearly supports the extra time spent.

Must be on a separate calendar date

99358 cannot be billed on the same day as a face-to-face E/M service such as an office visit (e.g., 99202–99215).

The date of service must be distinct, and the prolonged service must not occur on the same calendar date as the related patient encounter.

Personally performed by provider

Services reported under 99358 must be directly performed by the physician or qualified healthcare professional. Work performed by clinical staff or support personnel does not qualify, even if medically necessary.

Supporting documentation for high volumes

If billing exceeds Medicare’s Medically Unlikely Edits (MUEs) or payer-imposed time thresholds, the documentation must include a clear rationale, clinical complexity, and justification for the prolonged services.

Applicable modifiers for CPT code 99358

While CPT 99358 does not always require modifiers, certain situations may call for them to ensure correct claims submission and avoid denials:

• Modifier 76 – Repeat procedure by same provider: Use this if the same provider repeats the prolonged service more than once in a single day, and each session is medically necessary.
• Modifier 77 – Repeat procedure by different provider: Use when another qualified healthcare professional provides the prolonged service on the same calendar date.
• Modifier 59 – Distinct procedural service: Apply this modifier only if no other modifier accurately describes the situation, such as when the service is distinct from other reported services.
• Modifier 91 – Repeat diagnostic lab test: Rarely applicable to 99358, but may be used in edge cases based on payer policy.

Other relevant CPT codes

Several related codes may be billed alongside or instead of 99358, depending on the nature and timing of the services provided:

• 99359 – Prolonged E/M services, each additional 30 minutes
• 99417 – Prolonged services on the same day as an outpatient office visit (used instead of 99358 when added time occurs during the face-to-face E/M visit)
• 99415–99416 – Clinical staff face-to-face prolonged services (used when prolonged services are performed by clinical staff under supervision)
• 99483 – Assessment and care planning for patients with cognitive impairment (used in conjunction with prolonged service codes for complex neurological or dementia care)
• 99497 – Advance care planning including discussion and documentation (may accompany prolonged service codes when extensive planning is involved)