Summary & Overview

CPT 83500: Free Hydroxyproline Measurement

CPT code 83500 represents a laboratory assay that measures free hydroxyproline in samples such as plasma, serum, urine, or cerebrospinal fluid. Clinically, the test is used to detect elevations of hydroxyproline associated with rare inherited or genetic disorders that affect collagen turnover; it is a targeted biochemical diagnostic tool rather than a routine screening test. Nationally, accurate coding and reporting of specialized biochemical assays like 83500 matters for diagnostic clarity, laboratory billing consistency, and appropriate clinical follow-up of uncommon metabolic conditions.

Key payers covered in this analysis include Aetna, Blue Cross Blue Shield, Cigna Health, UnitedHealthcare, and Medicare. Readers will find a concise overview of the clinical context for CPT code 83500, typical sites of service, and the service type. The publication summarizes how the code is positioned within laboratory service lines and highlights areas where payers and providers commonly focus, such as diagnostic indication and laboratory setting. Data not provided in the input are noted where applicable. This summary prepares clinical laboratory managers, billing professionals, and policy analysts to understand the code’s purpose and where to look for payer-specific coverage and billing guidance.

AetnaBlue Cross Blue ShieldCigna HealthUnitedHealthcareMedicare83500CPTlaboratoryhydroxyprolinebiochemical assaydiagnostic testingclinical laboratoryrare disease testing

Billing Code Overview

CPT code 83500 describes a laboratory measurement of free hydroxyproline in biological samples such as plasma, serum, urine, or cerebrospinal fluid. The test quantifies the amount of the amino acid hydroxyproline, which can be elevated in certain rare inherited or genetic disorders affecting collagen metabolism.

Service type: Clinical laboratory biochemical assay
Typical site of service: Clinical laboratory or hospital laboratory (specimen collected in outpatient or inpatient settings as appropriate)

Data not available in the input.

Clinical & Coding Specifications

Clinical Context

A typical patient is a child or adult referred for biochemical testing after suspicion of a rare metabolic or connective tissue disorder. The clinician suspects increased collagen degradation or an inherited disorder affecting collagen metabolism (for example, certain osteogenesis imperfecta variants or rare inherited connective tissue diseases). The patient presents with clinical features such as recurrent fractures, blue sclerae, joint laxity, poor wound healing, or unexplained elevated markers of bone turnover. The clinician orders laboratory assessment of free hydroxyproline in a sample (urine, plasma/serum, or cerebrospinal fluid) to quantify collagen breakdown.

The clinical workflow: the provider obtains informed consent when required, collects the appropriate specimen (commonly a timed urine collection or a serum sample), labels and transports the specimen to the clinical laboratory. The laboratory analyst performs the 83500 assay using validated biochemical methods, documents results in the laboratory information system, and posts a report to the ordering clinician. The ordering clinician interprets the hydroxyproline concentration in the clinical context, correlates with radiographic and genetic testing as indicated, and documents diagnostic or monitoring decisions in the medical record.

Coding Specifications

Modifier	Description	When to Use
`26`	Professional component	Use when billing only the professional interpretation portion if the lab separates professional and technical components.
`TC`	Technical component	Use when billing only the technical component (laboratory processing and analysis) without a professional interpretation.
`90`	Reference (outside) laboratory	Use when the test is performed by an outside/referral laboratory and results are reported by that lab.
`91`	Repeat clinical diagnostic laboratory test	(Note: `91` is not in the provided list; Data not available in the input.)
`90`	Reference (outside) laboratory	Duplicate entry suppressed per list — (Note: duplicate avoided).
`52`	Reduced services	Use when the lab performs a partial or limited version of the test relative to the full procedure.
`53`	Discontinued procedure	Use when specimen processing was started but the test was discontinued for documented clinical reasons.
`59`	Distinct procedural service	(Note: `59` is not in the provided list; Data not available in the input.)
`62`	Two surgeons	(Typically not applicable to lab testing)
`78`	Return to OR for related procedure	(Not applicable to lab testing)

Taxonomy Code	Specialty	Notes
207RH0000X	Clinical Laboratory	Medical technologists, clinical laboratory specialists who perform biochemical assays.
207K00000X	Pathology	Pathologists who oversee laboratory testing and validate results.
207L00000X	Clinical Cytogenetics (Laboratory Genetics)	Laboratory geneticists or biochemical geneticists involved when tests relate to inherited disorders.
208M00000X	Pediatrics	Pediatricians who order testing for congenital or inherited collagen disorders.
208D00000X	Family Medicine	Primary care clinicians who may order initial screening tests and coordinate referrals.

Related Diagnoses

ICD-10 Code	Description	Clinical Relevance
`M80.00`	Age-related osteoporosis with current pathological fracture, unspecified site	Osteoporosis with increased bone turnover can prompt assessment of collagen breakdown; hydroxyproline may be used adjunctively.
`M85.8`	Other specified disorders of bone density and structure	Used when rare structural bone disorders are considered; hydroxyproline can reflect collagen degradation.
`Q78.0`	Congenital osteogenesis imperfecta	Directly related inherited collagen disorder where hydroxyproline measurement may assist in biochemical evaluation.
`M35.8`	Other specified systemic involvement of connective tissue	Connective tissue disorders with suspected increased collagen breakdown.
`R79.89`	Other specified abnormal findings of blood chemistry	Non-specific abnormal chemistry prompting further metabolic testing including hydroxyproline.

Related CPT Codes

CPT Code	Description	Relationship to This Procedure
`81002`	Urinalysis, by dipstick or tablet reagent; non-automated, without microscopy	Performed as an initial urine screen; may precede urine collection procedures and specimen assessment for `83500` when urine is the specimen.
`83986`	Organic acids; qualitative, urine (e.g., gas chromatography/mass spectrometry)	May be ordered alongside metabolic testing when evaluating suspected inherited metabolic disorders contributing to abnormal collagen turnover.
`80305`	Drug screen, presumptive, any number of drug classes; any number of devices or procedures, non-instrumented	Not directly related but often part of broader toxicology panels when evaluating causes of bone or connective tissue abnormalities.
`82542`	Amino acids; other than plasma, qualitative or quantitative	Other amino acid assays that may be ordered in metabolic workups for inherited disorders affecting amino acid metabolism.