Billing code 88364: ISH probe stainMedicare rate & RVUs

Medicare pays $126.59 for 88364 nationally in the office. Local office rates run $111.71–$174.40.

Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.

What 88364 covers

This code covers an additional single-probe in situ hybridization stain procedure on a specimen after its initial probe stain. A pathology laboratory performs the probe-based testing on tissue or other submitted material, and a pathologist interprets the findings as part of the diagnostic workup. Fluorescence in situ hybridization (FISH) is a familiar example; the additional stain may assess another target on the specimen.

Report the code only with an eligible primary procedure, such as the initial single-probe stain, and count each additional probe stain procedure per specimen. The record should identify the specimen, the additional probe or target, and the testing performed. Medicare treats this as an add-on paid within the primary procedure’s global period. The global service is billed without a component modifier; modifier 26 reports the interpretation, while modifier TC reports the technical work, equipment, and staff. Both modifiers are separately priced under the CMS facts.

This summary was written with AI assistance from CMS physician fee schedule data and checked against the CMS billing rules shown here. Rates on this page come directly from CMS files.

Where 88364 pays more and less

The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.

109 of 109 payment localities

88364 rates by state

Office rate range in each state. Select a state to see its payment localities.

How the 88364 rate is calculated

Each of 88364’s three RVUs is multiplied by a geographic index (GPCI) for the payment locality, added up, and multiplied by the conversion factor. Drag the indexes or enter a ZIP to see what moves the rate.

Payment rules and modifiers for 88364

The CMS indicators that decide how 88364 is paid alongside other services.

What modifiers do to the payment

When to use modifier 26

88364 compared with similar codes

How to choose

88365In situ hybridization

88365 represents the initial single-probe stain on a specimen. Use 88364 for an additional single-probe stain procedure.

88366FISH interpretation

88366 reports interpretation and a report for in situ hybridization; 88364 represents the additional probe stain procedure itself.

88367ISH analysis

88367 reports manual morphometric analysis of in situ hybridization findings, rather than an additional probe stain procedure.

88368ISH analysis

88368 reports computer-assisted morphometric analysis; 88364 reports an additional single-probe stain procedure.

Codes related to 88364

Related codes aren’t interchangeable: bill the code that matches the service performed.

Where these rates come from

FeeBase calculates base physician payments from CMS work, practice-expense and malpractice RVUs, adjusted by each locality’s geographic indexes and the conversion factor. Services without a published rate are labeled, never given a made-up amount. Amounts are Medicare allowed amounts before claim adjustments: not a patient’s bill or a commercial rate.

CMS RVU26D · effective Oct 1, 2026 through the day before Jan 1, 2027

Open CMS sourceHow we calculate rates