CPT Code 88364Complete Billing & Coding Guide (2026)Insitu hybridization (fish)
About CPT 88364
CPT 88364 is a Current Procedural Terminology code in the Pathology/Lab category maintained by the American Medical Association. The CMS short descriptor reads "Insitu hybridization (fish)". For the full AMA long descriptor and clinical guidance, refer to the current CPT code manual.
Add-on codes cannot be billed alone and inherit their global period from the primary procedure. Payer scrubbers will reject add-on codes submitted without a valid base code on the same claim.
88364 has 2 NCCI bundling edit pairs documented. Run your scrubber against the NCCI quarterly update before submission. When clinically warranted, use modifier 59 or the X-modifiers (XE, XS, XP, XU) to bypass an indicator-1 edit, with chart documentation supporting the distinct service.
Code Properties
RVU Breakdown
Every CPT code’s Medicare payment is calculated from three Relative Value Unit components: physician work, practice expense, and malpractice. Together they multiply by the conversion factor to produce the payment amount.
Payment = Total RVU × Conversion Factor ($33.4009) × Geographic Adjustment (GPCI). National averages shown. Actual payment varies by locality.
Medicare Payment by State
Medicare adjusts payment by locality based on GPCI (Geographic Practice Cost Index). Higher cost-of-living areas like California and New York pay more. Rural states pay less. Top 12 states shown.
Showing top 12 of 53 states. Full locality data available in CMS PFS Locality file.
NCCI Bundling Edits
2 pairsThese codes trigger National Correct Coding Initiative edits when billed with 88364. An indicator of 0 means the pair cannot be unbundled. Indicator 1 means modifier 59 or X-modifiers may allow separate billing with supporting documentation.
88364 + 88346: bundled, modifier may bypass (indicator 1)
The most-asked bundling question on this code. Verdict pulled from the current NCCI quarterly file.
Modifier indicator 1 means a modifier may bypass the edit when the clinical scenario supports a distinct, separately identifiable service. Most billers default to modifier 59, but payers prefer the more specific X-modifiers (XE, XS, XP, XU) and pay them with less audit scrutiny. Documentation must establish the separation factor.
CPT Manual or CMS manual coding instruction
Billing 88364 alongside a bundled code without the correct modifier generates CARC 97 denials. Payers often flag these as audit risks. Document medical necessity for the separate service and apply modifier 59 or the appropriate X-modifier (XE, XS, XP, XU) only when clinically justified.
CPT Manual or CMS manual coding instruction
CPT Manual or CMS manual coding instruction
Bundling denials on 88364 are recoverable when the edit indicator is 1 and the chart documents a distinct, separately identifiable service. Our coders verify the indicator and pick the precise X-modifier (XE, XS, XP, XU) instead of defaulting to modifier 59.
Denied on 88364 + 88346 with the wrong modifier? Send us the EOB.
Most bundling denials on 88364 are recoverable when an X-modifier replaces a generic mod 59 and the chart supports a distinct service. A coder will read the EOB and the operative or procedure note for you.
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Applicable Modifiers
Modifiers commonly paired with 88364 based on its category. Apply only when the clinical circumstance warrants. Incorrect modifier use is a top audit target.
Component split modifiers (26 professional, TC technical) are the most under-applied modifiers in diagnostic billing. Practices that bill global on services where they only provided the read silently invite refund requests. We split components correctly at submission.
Supporting ICD-10 Diagnoses
These diagnosis codes commonly support medical necessity for CPT 88364. Using the correct ICD-10 prevents CARC 50 denials. Payer rejects when the diagnosis doesn’t support the procedure.
CARC 50 medical-necessity denials carry both rework cost and an audit-risk signal when patterns repeat. Our coders verify ICD-10 specificity and policy alignment at the coding stage so these losses get prevented upstream.
Find the revenue leakage in your 88364 claims.
Wrong modifier, missing documentation, bundling without justification, stale ICD-10 linkage: these are the silent revenue killers on Pathology/Lab claims. Our AAPC-certified team audits your last 90 days of 88364 claims, surfaces the recoverable dollars, and appeals them. Free, no obligation.
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Related CPT Codes
Codes in the same family as 88364
Everything about CPT 88364
What does CPT code 88364 cover?
CPT 88364 is a Current Procedural Terminology code in the Pathology/Lab category maintained by the American Medical Association. The CMS short descriptor reads "Insitu hybridization (fish)". For the full AMA long descriptor and clinical guidance, refer to the current CPT code manual.
What is the Medicare payment for CPT 88364?
The national average Medicare payment for CPT 88364 is approximately $126.59 in a non-facility setting and $126.59 in a facility setting. Actual payment varies by locality based on GPCI adjustments. Total RVU is 3.79 with a conversion factor of $33.4009.
What is the global period for CPT 88364?
CPT 88364 is an add-on code (indicator ZZZ). Its global period matches the base procedure it's billed with. Cannot be billed alone. Must be paired with a primary code per CPT guidelines.
What codes bundle with CPT 88364?
CPT 88364 has NCCI Procedure-to-Procedure edits with 2+ codes including 88346, 96523. Modifier indicator 0 means the edit cannot be bypassed. Indicator 1 means modifier 59 or X-modifiers may allow separate billing with documentation.
CPT codes and descriptions are copyright of the American Medical Association. RVU values reflect current CMS publications. Actual payment varies by locality. Commercial payer rates vary by contract.
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We audit your last 90 days of claims and surface the revenue leakage: wrong modifiers, missed bundling appeals, ICD-10 specificity gaps. AAPC-certified coders. 2.49% of collections. No setup fees.