CPT code 88364: ISH probe stain, each additional probe2026 Medicare rate & RVUs in Maryland
Reports an additional single-probe in situ hybridization stain on a specimen after the initial probe procedure, such as an additional FISH probe.
Medicare pays $128.00–$146.26 for 88364 in the office in Maryland, from Rest of Maryland to Washington, DC area. Which amount applies depends on the service address.
Medicare allowed amount for participating (non-QP) physicians, before deductible, coinsurance and claim adjustments. Not a patient’s bill or a hospital charge.
Your location
On this page 9 sections
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.
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 in Maryland
The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.
3 payment localities
$128.00 to $146.26
| Payment locality | Office | Facility |
|---|---|---|
| Baltimore area, MD | $134.65 | Unavailable |
| Rest of Maryland | $128.00 | Unavailable |
| Washington, DC area | $146.26 | Unavailable |
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.
How the rate is built · 88364
RVUs × geographic indexes × conversion factor
Work0.68
0.68 RVUs× 1.000 GPCI
Practice expense3.09
3.09 RVUs× 1.000 GPCI
Malpractice0.02
0.02 RVUs× 1.000 GPCI
Adjusted RVUs
3.7900
Conversion factor
$33.4009
Medicare rate
$126.59
Every GPCI starts at 1.000, the national rate. Enter a ZIP or drag a slider.
Payment rules and modifiers for 88364
The CMS indicators that decide how 88364 is paid alongside other services.
CMS payment indicators · 88364
ISH probe stain, each additional probe
| Rule | CMS value | What it means |
|---|---|---|
| Global period | ZZZ | Add-on code: falls within the primary procedure’s global period. |
| Multiple procedures | 0 | No multiple-procedure reduction. |
| Bilateral (modifier 50) | 0 | The 150% bilateral adjustment doesn’t apply. |
| Assistant at surgery (80/81/82/AS) | 0 | Not paid without supporting documentation. |
| Co-surgeons (62) | 0 | Not permitted. |
| Team surgery (66) | 0 | Not permitted. |
| Professional/technical | 1 | Diagnostic test with separate professional (26) and technical (TC) components. |
What modifiers do to the payment
Modifier 26 · payment effect
With and without the modifier
88364 without 26 · national office
$126.59
ISH probe stain, each additional probe
88364-26 · Professional component
$31.73
Pays only the interpretation and report.
88364 compared with similar codes
Compare codes · National
5 codes, side by side
How to choose
- 88365In situ hybridizationManual probe stain
- 88365 represents the initial single-probe stain on a specimen. Use 88364 for an additional single-probe stain procedure.
- 88366FISH interpretationInterpretation and report
- 88366 reports interpretation and a report for in situ hybridization; 88364 represents the additional probe stain procedure itself.
- 88367ISH analysisAutomated morphometric analysis
- 88367 reports manual morphometric analysis of in situ hybridization findings, rather than an additional probe stain procedure.
- 88368ISH analysisManual, initial probe
- 88368 reports computer-assisted morphometric analysis; 88364 reports an additional single-probe stain procedure.
88364 billing questions
When is this code used instead of the initial-probe code?
Use it for each additional single-probe stain procedure on a specimen after the initial probe procedure. The initial stain is reported with 88365.
Can this code be billed by itself?
No. It is an add-on code and must be reported with an eligible primary procedure, such as the initial probe stain.
How are units counted?
Count each additional single-probe stain procedure per specimen. Document the specimen and the additional probe or target tested.
When should modifier 26 or TC be used?
Use modifier 26 for the professional interpretation or TC for the technical work, equipment, and staff. Without either modifier, the claim represents the global service.
What documentation supports an additional-probe claim?
The record should show which specimen received testing, the additional probe or target, and that the service was an additional stain procedure beyond the initial probe.
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
Show the CMS file lines behind this rate
Fee sheets · Coming soon
Put 88364 and the rest of your codes on one sheet
Your codes at your locality, with payer contracts beside Medicare.
Join the waitlist