Laboratory Billing Cheat Sheet (2026)
Laboratory and pathology billing concentrates risk in two places: the professional and technical split that decides what the practice keeps, and the stain and immunohistochemistry units that get miscounted. Add strict medical-necessity policies and the margin for error is small.
Quick reference for laboratory billers. Last updated .
Top Laboratory CPT Codes & 2026 Medicare Allowables
| Code | Description | Non-Facility | Facility | Total RVU |
|---|---|---|---|---|
| 88305 | Surgical pathology, gross and microscopic, level IV | $70.14 | $70.14 | 2.10 |
| 88304 | Surgical pathology, gross and microscopic, level III | $41.08 | $41.08 | 1.23 |
| 88307 | Surgical pathology, gross and microscopic, level V | $277.90 | $277.90 | 8.32 |
| 88309 | Surgical pathology, gross and microscopic, level VI | $413.50 | $413.50 | 12.38 |
| 88312 | Special stains, group I (microorganisms) | $109.55 | $109.55 | 3.28 |
| 88313 | Special stains, group II (other than enzymes/microorganisms) | $80.83 | $80.83 | 2.42 |
| 88341 | Immunohistochemistry, each additional single antibody | $94.19 | $94.19 | 2.82 |
| 88342 | Immunohistochemistry, first single antibody stain | $110.22 | $110.22 | 3.30 |
| 88112 | Cytopathology, selective cellular enhancement, interpretation | $65.47 | $65.47 | 1.96 |
| 88160 | Cytopathology smears, any other source, screening and interpretation | $81.50 | $81.50 | 2.44 |
| 88173 | Cytopathology, fine needle aspirate, interpretation and report | $166.67 | $166.67 | 4.99 |
| 89220 | Sputum specimen collection by induction | $21.04 | $21.04 | 0.63 |
National 2026 Medicare Physician Fee Schedule estimates (total RVU multiplied by the conversion factor). These are adjusted by state locality. See the per-state table on the Laboratory billing services page.
Modifiers That Prevent Laboratory Denials
The pathologist's professional interpretation only, when the practice does not own the technical component.
The technical component only, when the lab performs the technical work but does not interpret.
A distinct test or service separate from another that NCCI would otherwise bundle.
A repeat clinical diagnostic lab test to obtain subsequent results, not to confirm or rerun the first.
A test referred to and performed by an outside laboratory and billed by the referring entity where permitted.
An ABN is on file (GA) or expected denial with no ABN (GZ) for a test likely to fail medical necessity.
Top Laboratory Denials → Quick Fix
Bill modifier 26 for the pathologist interpretation only when the practice does not own the technical component. Global billing double-counts and denies.
88342 is the first single antibody stain and 88341 each additional; multiplex uses 88344. Document each antibody and method so the units match the work.
88312 and 88313 are billed per stain group per specimen. Document the stain group and the block or specimen so the units are supportable.
Link a covered diagnosis meeting the national or local coverage policy for the test. Screening or reflex tests without a covered indication are denied.
Append modifier 91 for a medically necessary repeat to obtain subsequent results, with the clinical reason, so it is not rejected as an exact duplicate.
NCCI Bundling Watch-Outs
Code pairs from this specialty's set that carry NCCI edits. Billing both without a justified modifier triggers a bundling denial.
| Code | Bundles With | Rationale |
|---|---|---|
| 88305 | 88160 | More extensive procedure |
| 88305 | 88161 | More extensive procedure |
| 88304 | 88160 | More extensive procedure |
| 88304 | 88161 | More extensive procedure |
| 88307 | 88160 | More extensive procedure |
| 88307 | 88161 | More extensive procedure |
| 88309 | 88160 | More extensive procedure |
| 88309 | 88161 | More extensive procedure |
Documentation That Holds Up on Appeal
The specimen and the level of service, since the code level is specimen-driven.
Each antibody stained and the method, since the codes are per-antibody units.
The stain group and the block or specimen, since billing is per stain group per specimen.
The ordering diagnosis that meets the coverage policy, and an ABN where the test may not meet necessity.
Whether the practice owns the technical component and who interpreted, supporting 26, TC, or global.
Revenue Laboratory Practices Leave on the Table
Billing globally for interpretation-only work, which double-counts the technical component and denies.
Undercounting immunohistochemistry and special stain units against the antibodies and groups actually performed.
Necessity denials because the ordering diagnosis did not meet the coverage policy and no ABN was obtained.
Repeat tests rejected as duplicates because modifier 91 and the clinical reason were omitted.
Laboratory Billing FAQ
When do I use modifier 26 versus TC for pathology?
26 when the pathologist interprets a specimen the practice did not technically process, TC when the lab does the technical work without interpreting, and global only when the practice owns and performs both.
How are immunohistochemistry stains billed?
88342 for the first single antibody, 88341 for each additional single antibody, and 88344 for multiplex. Each antibody and the method have to be documented so the units match the work performed.
Why do lab tests deny for medical necessity?
Because the ordering diagnosis did not meet the national or local coverage policy for the test. A covered indication has to be linked, and an ABN obtained when the test may not meet necessity.
How do I bill a medically necessary repeat test?
Append modifier 91 with the clinical reason for obtaining subsequent results. Without it the repeat is rejected as an exact duplicate.
Stop Losing Laboratory Revenue to Preventable Denials
Our AAPC-certified laboratory coders apply every rule on this sheet to your claims. Call 888-701-6090 for a free billing assessment.