Summary & Overview

CPT 83505: Total Hydroxyproline, 24-Hour Urine

CPT code 83505 identifies a quantitative laboratory assay for total hydroxyproline, usually measured in a 24-hour urine specimen to evaluate collagen turnover and bone metabolic activity. Nationally, this specialized biochemical test is relevant for monitoring conditions that affect collagen degradation and bone remodeling, including metabolic bone disease and disorders that alter collagen metabolism. Its use informs clinical decisions about bone activity and disease progression rather than serving as a general screening tool.

Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of clinical context, common sites of service, and the role of the assay in diagnostic workflows. The publication summarizes how payers typically position coverage for specialized biochemical assays and provides benchmarking context where available. Topics addressed include clinical indications for ordering the test, typical laboratory workflows, and payer considerations relevant to coverage and claims processing.

This nationally focused summary is intended for clinicians, laboratory directors, and billing professionals who need a clear description of what CPT code 83505 represents, why the assay matters clinically, and what to expect operationally when this test is ordered.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicareCPT 83505hydroxyprolineurine assayclinical laboratorybone metabolismbiochemical assaylaboratory billingdiagnostic testing

Billing Code Overview

CPT code 83505 measures the total hydroxyproline level, typically performed on a 24-hour urine specimen. The test quantifies hydroxyproline, an amino acid derived from collagen breakdown, and is used to assess collagen turnover and bone metabolic activity.

Service type: Clinical laboratory test — quantitative biochemical assay

Typical site of service: Clinical laboratory or hospital laboratory, using outpatient urine collection

Clinical & Coding Specifications

Clinical Context

A typical patient is a postmenopausal woman or an adult with suspected metabolic bone disease referred for biochemical assessment of bone turnover. The clinician orders 83505 (total hydroxyproline measurement) when there is concern for increased collagen degradation as seen with osteoporosis, Paget disease, hyperparathyroidism, bone metastases, or monitoring response to antiresorptive therapy. The patient collects a 24‑hour urine specimen following lab instructions and returns it to the outpatient laboratory or hospital clinical laboratory. The laboratory analyst receives the specimen, documents completeness of the collection, performs any required specimen processing (aliquoting, centrifugation), and runs the hydroxyproline assay. Results are reported to the ordering provider with reference intervals and interpretation comments as appropriate for assessing collagen turnover and bone activity. Typical sites of service are outpatient laboratory, hospital clinical laboratory, or an ambulatory diagnostic center.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when only the professional component of the test is billed separately from the technical component.
`TC`

Taxonomy Code	Specialty	Notes
363A00000X	Clinical Pathology	Clinical pathologists oversee laboratory testing, interpretation, and quality control for `83505`.
207K00000X	Endocrinology	Endocrinologists commonly order hydroxyproline testing for metabolic bone disease assessment.
2080P0005X	Family Medicine	Primary care clinicians often initiate the test as part of osteoporosis workup or monitoring.
207L00000X	Rheumatology	Rheumatologists may use the test when evaluating systemic connective tissue disorders that affect collagen turnover.

CPT Code	Description	Relationship to This Procedure
`81000`	Urinalysis, by dipstick or tablet reagent; non-automated, with microscopy	Performed as an initial screening of urine specimen quality prior to a 24-hour collection for `83505`.
`81025`	Urine pregnancy test, by visual color comparison methods	May be performed prior to collecting a 24-hour urine in women of childbearing potential.
`85025`	Blood count; automated complete CBC with automated differential	Used adjunctively to evaluate overall patient health when assessing bone disease causes.
`82040`	Assay of urinary calcium, qualitative or semiquantitative	Often ordered alongside `83505` to assess bone resorption and calcium excretion.
`83986`	Assay of urinary creatinine, quantitative	Performed on the 24‑hour urine to validate completeness of the collection and to normalize hydroxyproline excretion.

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