Billing code 88121: Urine FISHMedicare rate & RVUs in Illinois
Computer-assisted in situ hybridization evaluates urinary tract cells with three to five probes, typically supporting assessment or surveillance for urothelial carcinoma.
Medicare pays $363.25–$404.77 for 88121 in the office in Illinois, from Rest Of Illinois to Suburban Chicago. 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.
On this page 9 sections
What 88121 covers
88121 represents computer-assisted cytopathologic analysis of a urinary tract specimen using in situ hybridization with a panel of three to five probes. The method evaluates probe signals in urothelial cells for chromosomal changes associated with urothelial carcinoma; it may be used when evaluating hematuria or monitoring a patient with a history of bladder cancer. Laboratory staff prepare and analyze the specimen, with a pathologist or other qualified professional interpreting the findings. Pathology and molecular diagnostic laboratories commonly perform this service.
Report one unit for each specimen examined. Documentation should identify the urinary specimen, the probe panel and count, the computer-assisted method, and the interpretation. This distinguishes 88121 from 88120, which describes the corresponding service without computer assistance. CMS recognizes professional and technical components: modifier 26 identifies interpretation, modifier TC identifies equipment and staff, and billing without either modifier represents the global service.
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 88121 pays more and less in Illinois
The same RVUs, adjusted for each area’s costs. Open a locality for its calculation, history and nearby areas.
4 payment localities
$363.25 to $404.77
| Payment locality | Office | Facility |
|---|---|---|
| Chicago | $397.55 | Unavailable |
| East St. Louis | $366.37 | Unavailable |
| Rest Of Illinois | $363.25 | Unavailable |
| Suburban Chicago | $404.77 | Unavailable |
How the 88121 rate is calculated
Each of 88121’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 · 88121
RVUs × geographic indexes × conversion factor
Swap in your local Medicare rate.
Work 0.98Practice expense 10.77Malpractice 0.04
All indexes start at 1.000 (the national rate). Enter a ZIP or drag a slider.
Payment rules and modifiers for 88121
The CMS indicators that decide how 88121 is paid alongside other services.
CMS payment indicators · 88121
Urine FISH
| Rule | CMS value | What it means |
|---|---|---|
| Global period | XXX | The global surgery concept doesn’t apply. |
| 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
88121 without 26 · national office
$393.80
Urine FISH
88121-26 · Professional component
$45.43
Pays only the interpretation and report.
88121 compared with similar codes
Compare codes
88121 vs 88120 vs 88112 vs 88104: national Medicare rates
Swap in your local Medicare rate.
How to choose
- 88120Urine FISH
- Choose 88121 when the urinary in situ hybridization analysis is computer-assisted. 88120 describes the corresponding three-to-five-probe service without computer assistance.
- 88112Selective-enhancement cytology
- 88112 is a cell-enhanced cytology examination focused on cell morphology. 88121 is a probe-based molecular analysis of a urinary tract specimen.
- 88104Fluid cytology
- 88104 reports morphologic examination of a fluid or washing smear. 88121 reports computer-assisted in situ hybridization with three to five probes.
88121 billing questions
How does 88121 differ from 88120?
Both involve urinary tract specimens and three to five probes. 88121 is the computer-assisted service; 88120 is the corresponding service without computer assistance.
How many units should be reported?
Report one unit for each specimen examined. The three-to-five-probe range describes the panel for the service, not the number of units.
Which modifiers identify the components?
Use modifier 26 for the professional interpretation and modifier TC for the technical service involving equipment and staff. Without either modifier, the claim represents the global service.
Can 88121 be reported with conventional urine cytology?
88121 represents molecular in situ hybridization, while conventional cytology evaluates cell morphology. Report both only when both distinct services were performed and documented.
What documentation supports reporting 88121?
Record the urinary tract specimen, the computer-assisted in situ hybridization method, the three-to-five-probe panel, and the professional interpretation when that component is billed.
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
Put 88121 and the rest of your codes on one sheet
Build a fee sheet from your own code list at your locality, put your payer contracts beside Medicare, and see what changed each quarter.
Build my fee sheetOr price your code list free →