Summary & Overview
CPT 0058U: Merkel SmT Oncoprotein Antibody Titer
CPT code 0058U designates the Merkel SmT Oncoprotein Antibody Titer, a Proprietary Laboratory Analyses (PLA) test performed by the University of Washington’s Department of Laboratory Medicine to detect and quantify antibodies to the Merkel cell polyomavirus small T antigen. The assay targets a tumor-specific oncoprotein relevant to Merkel cell carcinoma (MCC), a rare but highly aggressive neuroendocrine skin cancer; as a PLA, the code applies only to this specific test and provider.
This national-level summary highlights coverage and policy relevance for major payers, with Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare included in the overview. The publication describes clinical context for use in MCC surveillance and diagnosis, summarizes typical sites of service and service type, and outlines what readers will find in the full report: payer coverage benchmarks, coding and billing considerations, and clinical context for interpretation.
Readers will learn where CPT code 0058U fits in laboratory service lines, how PLA status affects coding and billing, and the practical implications for hospital and outpatient laboratory operations. Data not available in the input is noted where specific payer coverage determinations, reimbursement rates, and associated taxonomies or ICD-10 linkage are not provided.
Billing Code Overview
CPT code 0058U is a Proprietary Laboratory Analyses (PLA) code for the Merkel SmT Oncoprotein Antibody Titer developed by the University of Washington’s Department of Laboratory Medicine. The test detects and quantifies antibodies to the Merkel cell (MC) polyomavirus small T (sT) antigen/oncoprotein, a key oncogenic driver implicated in Merkel cell carcinoma (MCC), an aggressive neuroendocrine skin cancer.
Service Type: Laboratory diagnostic serology — proprietary antibody quantification
Typical Site of Service: Clinical laboratory or hospital laboratory setting; sample collection commonly performed in outpatient phlebotomy or hospital outpatient drawing stations.
Clinical & Coding Specifications
Clinical Context
A 68-year-old patient with a history of a rapidly growing, firm, painless cutaneous nodule on the forearm is diagnosed with Merkel cell carcinoma (MCC) by biopsy. The treating dermatologic oncologist orders the Merkel SmT Oncoprotein Antibody Titer performed by the University of Washington Department of Laboratory Medicine to detect and quantify antibodies to the Merkel cell polyomavirus small T (sT) antigen. The test is used as a tumor-associated serologic marker to aid in baseline staging, to help assess tumor burden, and to monitor disease recurrence or response during surveillance after definitive therapy (surgery, radiation, or systemic therapy).
Typical clinical workflow:
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Patient evaluated in dermatology or oncology clinic; biopsy confirms MCC.
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Order placed for proprietary laboratory test
0058Uwith clinical indication of MCC and intent (baseline serology or surveillance). -
Blood draw performed in outpatient phlebotomy or oncology infusion center; specimen shipped per University of Washington instructions.
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Laboratory performs proprietary assay and reports quantitative sT antibody titer; result is returned to ordering clinician and placed in the medical record.
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Clinician interprets titer in the context of imaging, pathology, and clinical exam to inform surveillance intervals and assessment of treatment response.
Coding Specifications
| Modifier | Description | When to Use |
|---|---|---|
00 | Default/No modifier | General reporting when no specific modifier applies |
26 | Professional component | When billing separately for the professional interpretation component, if applicable |
TC | Technical component | When billing only the technical component of the laboratory assay |
52 | Reduced services | If the assay was partially completed or a reduced service was performed |
53 | Discontinued procedure | If specimen collection or processing was initiated but discontinued for valid clinical reasons |
59 | Data not available in the input. | Data not available in the input. |
AD | Advanced beneficiary notice (ABN) indicator | When an ABN is on file indicating patient may be liable for the test |
QK | CLIA waived test performed by a physician | If the performing lab meets conditions for this QA modifier (rare for PLA) |
QX | CLIA non-waived test performed by a qualified person | When the test requires high complexity testing personnel |
QY | Documentation only; test ordered by physician | When documentation supports test ordering under certain payor policies |
SH | Digital or remote services - data not applicable | Data not available in the input. |
SJ | Data not applicable | Data not available in the input. |
TG | Pathology other than surgical pathology | When the test is reported in conjunction with pathology services |
| Taxonomy Code | Specialty | Notes |
|---|---|---|
| 207RH0000X | Hematology & Oncology | Medical oncologists ordering and interpreting surveillance assays |
| 207Q00000X | Surgical Oncology | Surgical oncologists managing MCC patients and follow-up |
| 207P00000X | Dermatology | Dermatologists diagnosing MCC and initiating testing |
| 208000000X | Pathology | Pathologists involved in test validation and interpretation |
| 363L00000X | Clinical Laboratory | Clinical laboratory directors or specialists overseeing testing procedures |
Related Diagnoses
| ICD-10 Code | Description | Clinical Relevance |
|---|---|---|
C4A.0 | Merkel cell carcinoma of skin: Data not available in the input. | Data not available in the input. |
C44.99 | Other and unspecified malignant neoplasm of skin, unspecified site | Used when MCC is coded under unspecified skin malignancy pending precise site coding |
C80.1 | Malignant (primary) neoplasm, unspecified | Used in atypical presentations or when primary site uncertain at time of testing |
Z85.828 | Personal history of malignant neoplasm of skin | Relevant for surveillance testing in patients with prior MCC |
R92.8 | Other abnormal and inconclusive findings on diagnostic imaging of breast and skin | Used when imaging findings prompt additional serologic surveillance |
Related CPT Codes
| CPT Code | Description | Relationship to This Procedure |
|---|---|---|
86318 | Antibody; infectious agent antigen detection by enzyme immunoassay technique, qualitative or semiquantitative | Common serologic platform used for other antibody assays; conceptually similar immunoassay methodology though not specific to this PLA |
86850 | Tissue identification by immunoassay technique | Complementary tissue-based testing in MCC diagnostic workflows when correlating serology with tumor antigen expression |
88305 | Pathology, surgical; level IV - surgical pathology, gross and microscopic examination | Performed on the diagnostic biopsy or excision specimen that establishes MCC diagnosis prior to ordering 0058U |
96413 | Chemotherapy administration, intravenous infusion, for therapeutic drugs | Systemic therapy administration CPT that may occur as part of MCC treatment alongside surveillance with 0058U |
77334 | Radiation therapy; complex treatment devices and calculations (per treatment) | Radiation therapy delivery CPT often used in definitive or adjuvant treatment of MCC; serologic monitoring with 0058U may occur during follow-up |